• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12
  13. 13
    13
  14. 14
    14
  15. 15
    15
  16. 16
    16
  17. 17
    17
  18. 18
    18
  19. 19
    19
  20. 20
    20
  21. 21
    21

Periodic table

Free essay example:

Chemistry

In the beginning a long time ago before cars and mobile phones, students spent all day learning about the matter that made up the earth. They had long lessons, wore funny clothes and only had religious holidays.

Alchemists people who made up weird potions to live forever or make gold.

At the same time a man named Democritus (A teacher) suggested everything in the world was made up of tiny particles that could not be seen. He called them atoms

2000 years later Democritus idea was correct.

Scientists today don’t rely on weird potions and secret spaces with cauldrons instead they rely on investigations carried out with careful observations.  

Today there are 112 known elements

Building Blocks

Atoms are joined together in groups called molecules

Atoms can join together to form elements or large molecules of many different shapes

Polymer scientific word to describe large molecules e.g. Rubber, Cotton

Questions

  1. What is a molecule? Name the 2 compounds that are made up of molecules?
    Groups of atoms joined together, Carbon dioxide (CO
    2) and Water (H20)
  2.  Are all compounds made up of molecules? explain
    No some can exist in their natural form on their own
  3. Name 4 elements that occur naturally as molecules
    Carbon Dioxide (CO
    2) and Water (H20) Methane and ozone
  4. What are polymers? Give three examples
    Large Molecules eg plastics. glass and paint

Atoms

The particles in the centre of the atom are called protons (+) and neutrons (neutral)

Together they form the nucleus

Moving rapidly around the nucleus are tiny little electrons (-) arranged in shells

Number of protons = Number of electrons

The number of protons in an atom is called its atomic number

The atomic number tells us what element it is

Naming Elements as individuals

O = Oxygen, C = Carbon, N = Nitrogen

When there is more than one element

Cl = Chlorine
Ca = Calcium

Cu = Copper

If there is an element that has a symbol that doesn’t match

Na = Sodium

Pb = Lead

Ag = Silver

Periodic table

As early scientist discovered more and more elements they had to think of a way to organise them. Each element was given a name and a number

Dmitiri Meneleev a Russian scientist organised a system called the periodic table

Scientist today used a modified version of this table       image00.jpg

The group number is the number of electrons in the outside shell

The period number refers to the outermost shell containing electrons

The atomic number is the Protons and the neutrons in an atom

Inert Gases gasses which don’t change or mix

Noble gasses which cannot be mixed with other gasses

First 20 elements

  1. Hydrogen H
  2. Helium He
  3. Lithium LI
  4. Beryllium Be
  5. Boron B
  6. Carbon C
  7. Nitrogen N
  8. Oxygen O
  9. Fluorine F
  10. Neon Ne
  11. Sodium NA
  12. Magnesium Mg
  13. Aluminium Al
  14. Silicon Si
  15. Phosphorus P
  16. Sulphur S
  17. Chlorine Cl
  18. Argon Ar
  19. Potassium K
  20. Calcium Ca

The Nucleus

The atomic number is the number of protons present in each atom. Atoms with same atomic number have identical chemical properties. Mass number is the sum of the number of protons and neutrons in the atom. The number of neutrons in an atom can be calculated by subtracting the atomic number from the mass number.

A = the mass number

Z = the atomic number

E = symbol of the element

E.g. find the number of neutrons calcium has.

Atomic number - 40.08

Mass number – 20

Number of neutrons = 40.08 – 20 = 20.08

It is difficult to measure and compare the mass of atoms because of their extremely small size. So we try to compare the equal numbers of atoms rather than trying to measure the mass of a single atom. However a problem arises when not all atoms of an element are identical. Some elements may contain atoms with slightly different masses called isotopes. This is worked out as an average rather than a whole number.

Most elements exist as two or more isotopes. Isotopes all have the same chemical properties, but slightly different masses. When the protons and neutrons are held tightly together the nuclei are stable when they are not they are unstable.

Unstable isotopes disintegrate to form other substances which are radioactive. Some atoms are naturally radioactive; others have to be made active and are called artificial.

The energy emitted by radioactive substances is called nuclear radiation.

3 types of nuclear radiation:

Alpha – alpha particles are helium nuclei that contain 2 protons and 2 neutrons. Positively charged and cannot travel through materials easily. E.g. human skin and paper. Little hazard

Beta: beta particles are the same size and mass as electrons. They can have a positive or negative charge. Can penetrate human skin and damage cells. Do not penetrate thin layers of plastic, wood or aluminium

Gamma rays: not particles but bursts of energy which is released when alpha or beta particles are emitted. They travel at the speed of light and highly penetrate. They cause serious and permanent damage to the human body.

image01.jpg

Shell Diagrams

  • When atoms come in contact with each other, they often join together to form molecules. Other atoms join together to from giant crystals that contain billions of atoms.
  • It is the electrons in each atom that account for the chemical behaviour of all matter, because they form the outermost part of the atom.
  • An electron shell diagram is a simplified model of an atom. In these diagrams the nucleus of the atom, containing protons and neutrons is drawn in the middle. Electrons are arranged in a series of energy levels around the nucleus in shells.
  1. First shell holds only 2 electrons (K)
  2. Second shell holds up to 8 electrons (L)
  3. Third shell holds up to 18 electrons (M)
  4. Fourth shell holds up to 32 electrons (N)
  • The Outside shell can only ever hold 8 electrons
  • The following equation is used to calculate the maximum number of electrons in each shell. The xth shell holds a maximum of 2x2
  • The number of electrons in a shell corresponds to the number of period numbers on the periodic table. When Mendeleev and Meyer grouped the elements they had no idea that electrons existed. E.g. Group number 1 electrons contain 1 electron in the outer shell.
  • If an atom is given enough energy e.g. heat, the electrons will be able to move from one shell to another. Electrons move from a place of either higher energy to a place of lower energy and vice versa.
  • Knowledge of the outer shell helps us understand how compounds form. E.g. Sodium chloride (salt) forms when Sodium gives and electron to Chlorine, therefore giving chlorine a full outer shell. This then forms an ion.
  • Ions form when an atom looses or gains an electron to get a full outer shell. Atoms without 8 electrons in their outer shell are unstable whereas atoms with a full outer shell are stable.
  • Positive ions are called Cations and negative ions are called anions

Drawing and Writing Configurations

  • Ionic compounds form when atoms gain or lose electrons. Atoms can gain stability by sharing electrons. When two or more atoms share electrons a molecule is formed.
  • A chemical bond formed by the sharing of electrons is called a covalent bond. Non-metals share electrons to form covalent bonds. E.g. oxygen works best when two oxygen atoms share.
  • Electron dot diagrams are used to show how electrons are arranged. The atoms are drawn showing the outer shell only.
  • Most covalent compounds have the following properties.
  • They exist as gases, liquids or solids with low melting points because the forces of attraction between the molecules are weak.
  • They generally do not conduct electricity because they are not made up of ions.
  • They are often insoluble in water.
  • A molecular formula is the way of describing the number and type of atoms that join to form a molecule.
  • The formula of a compound shows the symbols of the elements that have combined to make the compound, and the ratio in which the atoms have joined together. E.g. CaCl2 which means 2 chlorine ions for every calcium ion.
  • The valency of an element is equal to the number of electrons that atom needs to gain, lose or share to fill its outer shell. If electrons are lost the valency it + and if electrons are gained the valency is -. E.g. Cl-1, Mg-2


Atoms:

Atoms – tiny indestructible particles

Protons - The positively charged particles in the centre of the atom

Neutrons - The neutrally charged particles in the centre of the atom

Nucleus – very small and dense centre of an atom, it contains protons and neutrons

Electrons – Move rapidly around the nucleus, are arranged in shells, they are negatively charged

First 20 elements:

  1. Hydrogen -  H
  2. Helium - He
  3. Lithium - LI
  4. Beryllium - Be
  5. Boron - B
  6. Carbon - C
  7. Nitrogen - N
  8. Oxygen - O
  9. Fluorine - F
  10. Neon - Ne
  11. Sodium - NA
  12. Magnesium - Mg
  13. Aluminium - Al
  14. Silicon - Si
  15. Phosphorus - P
  16. Sulphur - S
  17. Chlorine - Cl
  18. Argon - Ar
  19. Potassium - K
  20. Calcium - Ca

The group number is the number of electrons in the outside shell.

The period number refers to the number of shells containing electrons.

The atomic number is the Protons and the neutrons in an atom.

Dimitri Mendeleev – was a teacher of chemistry, he attempted to classify the elements according to their chemical properties, and he noticed patterns that led him to propose his Periodic Table.

Radioactive Isotopes - Some elements may contain atoms with slightly different masses called isotopes

Stable and unstable isotopes - When the protons and neutrons are held tightly together the nuclei are stable when they are not they are unstable.

Unstable isotopes disintegrate to form other substances which are radioactive.

3 types of nuclear radiation:

Alpha: alpha particles are helium nuclei that contain 2 protons and 2 neutrons. Positively charged and cannot travel through materials easily. E.g. human skin and paper. Little hazard

Beta: beta particles are the same size and mass as electrons. They can have a positive or negative charge. Can penetrate human skin and damage cells. Do not penetrate thin layers of plastic, wood or aluminium

Gamma rays: not particles but bursts of energy which is released when alpha or beta particles are emitted. They travel at the speed of light and highly penetrate. They cause serious and permanent damage to the human body.

Binary Fission – when an atom is split into two or more smaller nuclei. For example when splitting uranium – neutrons are fired at the radioactive uranium this causes the nuclei to split and form two new elements – this then releases neutrons, radiation and heat.

An electron shell diagram is a simplified model of an atom. In these diagrams the nucleus of the atom, containing protons and neutrons is drawn in the middle. Electrons are arranged in a series of energy levels around the nucleus in shells.

  1. First shell holds only 2 electrons (K)
  2. Second shell holds up to 8 electrons (L)
  3. Third shell holds up to 18 electrons (M)
  4. Fourth shell holds up to 32 electrons (N)

The Outside shell can only ever hold 8 electrons

The following equation is used to calculate the maximum number of electrons in each shell. The xth shell holds a maximum of 2x2

Knowledge of the outer shell helps us understand how compounds form. E.g. Sodium chloride (salt) forms when Sodium gives and electron to Chlorine, therefore giving chlorine a full outer shell. This then forms an ion.

Ions form when an atom looses or gains an electron to get a full outer shell. Atoms without 8 electrons in their outer shell are unstable whereas atoms with a full outer shell are stable.

Positive ions are called Cations and negative ions are called anions

Ionic Compounds - when atoms come into contact and lose or gain electrons and form a compound they are known as ionic compounds. Ionic compounds form when metal and non-metal atoms combine.

Electron Dot Diagrams – they only show the symbol of the atom and use dots for the Outer shell of atoms. They don’t show all the shells only the outer ones.

E.g.

image02.png

=    image03.png

Most covalent compounds have the following properties.

  • They exist as gases, liquids or solids with low melting points because the forces of attraction between the molecules are weak.
  • They generally do not conduct electricity because they are not made up of ions.
  • They are often insoluble in water.

The formula of a compound shows the symbols of the elements that have combined to make the compound, and the ratio in which the atoms have joined together. E.g. CaCl2 which means 2 chlorine ions for every calcium ion.

Water covalent bonding:

             O

          /     \    

        H       H  

= The hydrogen atoms share one electron each and the oxygen needs two                                      to get a full outer shell

  •  Single Bond – shares only one electron to gain a full shell.
  •  Double bond – shares two electrons to gain a full shell.
  • Triple Bond – shares three electrons to gain a full shell.

The valency of an element is equal to the number of electrons that atom needs to gain, lose or share to fill its outer shell. If electrons are lost the valency it + and if electrons are gained the valency is -. E.g. Cl-1, Mg-2

Reactants – the original chemicals in a reaction – Reactants are on the left hand side in an equation

Products – the new substances or chemicals produced – Products are on the right hand side of an equation

Note – Both were found by Antoine-Laurent Lavoisier

Law of Conservation of Mass – states that matter can neither be created nor destroyed during a chemical reaction.

Law of Constant Proportions – states that a compound no matter how it is formed always contains the same relative amounts of each element. E.g. Carbon Dioxide will always have 2 oxygen atoms in it no matter how it is formed.  

Physical change – no new substances are formed e.g. when ice melts it doesn’t form a new substance it is still water and they can be gotten back for example the water can be frozen to form ice again

Chemical change – new substances are formed and once they are formed you can’t get the original substance back.

Exothermic reactions – chemical reactions which give out energy. (Warm)

Endothermic Reactions – chemical reactions which absorb energy. (Cold)

Precipitate – when an ionic compound is unable to dissolve in water it forms a precipitate.

Corrosion – when metal is eaten away by substances in the air or water.

Displacement Reactions – when an element displaces another element. E.g. when silver is removed from silver nitrate solution by putting copper in it.

Combustion Reactions – when a substance reacts with oxygen and heat is released

Decomposition Reactions – when one single compound breaks down into two or more simpler chemicals

Combination reactions – when two elements combine in chemical reactions to form a compound

Redox Reactions – in many reactions electrons are either completely or partially transferred from one atom, ion or molecule to another. This process is known as electron transfer.

Chemical reactions which involve electron transfer are redox reactions.

In a redox reaction the loss of electrons is Oxidation, the gain of electrons is reduction.

Easy way to remember:

O – Oxidation

I - Is

L - Loss

R - Reduction

I - Is

G - Gain

When Metals react with acids =
Metal + Acid
 Salt + Hydrogen Gas

Acids – have a low pH level

Bases – have a high pH level

Alkalinity - measure of the ability of a solution to neutralize acids – Bases that can be dissolved in water are called alkalis

Neutralization – the reaction that takes place when an acid and a base are mixed – the substance becomes neutral it is neither an acid nor a base.

Examples of acids – hydrochloric acid, caustic soda, battery acid, gastric juices.

Peptic Ulcers:

What is it?

A break in a surface, whether it is on the skin, mucous membrane or the internal surface likes the stomach

How’s it caused?

By inflammation,

By bacteria and by effects of acid on the stomach

Symptoms:

Pain – Burning pain in lower stomach

Nausea

Vomiting

Loss of appetite

Weight loss

Weakness

Tiredness

Blood vessels may burst and bleed into your stomach – rapid bleeding into the stomach

How can it be diagnosed?

Endoscopy – small tube with a camera inserted down the esophagus to the stomach

Barium Meal – give you a special fluid then take an X-ray of the stomach

Urea Breath test – involves swallowing radioactive carbon and then testing the breath

Who found out the new cure? What does it mean?

Dr Robin Warren and Dr Barry Marshall

Discovered that a bacteria H Pylori (bacteria that lives in the lining of the stomach) caused ulcers and they could be cured by antibiotics

What it means:

Easier treatment

Patients have a normal life

Ulcers now curable

Catalysts:

Reactions can be sped up by:

Increasing the temperature

Increasing the surface are of solid reactants

The exposure to light

Using a catalyst

Catalysts:

Are chemicals – speed up reactions

Not changed by reaction

Same amount of catalysts left at the end as there was in the start

Catalysts help by making bonds break more easily – reactants use less energy – therefore reaction is faster

Catalysts can be recovered and used again

Biological catalysts found in our bodies are called enzymes

DNA – Cells

Cell theory:

  • States that all living things are composed of cells
  • States that cells are produced from pre-existing cells.

Cells are different in size, shape and in their organelles – however they have similar basic structures.

Organelles – very small structures in the cytoplasm, they are surrounded by a membrane and they each have a particular function. They work together to maintain the metabolic (life processes) of the cell.

Membrane – cells are surrounded by this

Cell Wall – plant, bacteria and fungi have this instead of a membrane

Eukaryotic cells – these each have a membrane bound nucleus and other organelles – animals, plants, fungi, protista.

Prokaryotic cells – bacterial cells that do not have a nucleus or other organelles held in membranes

Differentiated cells – some cells (mainly multi-cellular organisms) change during the lifespan to carry out a particular function. Some cells even die during this process. Examples include cells that make bone in mammals or those that carry water from the roots in plants.

Viruses dead or alive? Viruses do not have an organelle nor do they carry out processes common to cells that are alive. Viruses penetrate other cells and feed of their nucleic material – enables viruses to survive for longer, if a virus enters you it may never leave – lay dormant until the right time.

Biotechnology – describes the way we use plant and animal cells and micro-organisms to produce useful substances and to perform tasks for us.

An example of this is retting – where linen is made by putting flax inyo pits of water. The soft parts of the stem are decomposed by the action of micro-organisms.

Other examples include fermenting (making wine and beer etc.) and culturing (antibiotics are made this way – it is a controlled growth of micro-organisms on special nutrients – enabling large scale production of antibiotics)

Enzymes – large protein molecules

DNA and Chromosomes

Nucleus – a small organelle which is only visible under the electron microscope – contains the blueprints of life and keeps it going. Nucleus is separated from the rest of the cell by a nuclear membrane.

The nucleus contains chemical compounds called nucleic acid – DNA.

DNA – Deoxyribonucleic Acid, it is found in the nucleus. It carries coded instructins and ribonucleic acid – RNA. RNA allows DNA to read the coded instructions. DNA is responsible for most of our characteristics. About 1 metre of DNA in each cell – the DNA molecule looks like a double helix.

Watson and Crick worked out what the structure of DNA looked like in 1953

Chromosomes – when the cell is about to divide lengths of DNA called chromosomes shorten and coil. Each chromosome is made up of two strands or chromatids and they are held together by the centromere.  

During cell division – chromosomes become single stranded – later they become double stranded again – this ensures that the DNA molecule has been replicated exactly and that characteristics are passed on unchanged.

Every living thing has chromosomes – kangaroos: 6 pairs, fruit fly: 4 pairs, humans 23 pairs.

Every cell in the human body will have 23 pairs of chromosomes or 46 pairs of chromatids.

Sex chromosome - contains all the info. For the sexual characteristics of the body. Males have a longer X sex chromosome and a shorter Y sex chromosome whereas females have two X sex chromosomes.

Autosomes – any chromosome that is not a sex chromosome.

Karyotyping – is the process of sorting out chromosomes into the matched pairs. Karyotyping is an important technique used in investigating chromosomal disorders. E.g. Down Syndrome.

Genes – sections of DNA which contain complete messages are known as genes. They are messages in code that provide the information for all cellular functions.

Genes determine:

  • Characteristics that are used to classify it into the plant or animal kingdom and into specific family and species
  • How it uses food
  • How well it fights infection
  • At times hot it behaves

Genes control the production of proteins that make up most of our body.  

How genes work:

Each organism has its own regulators i.e. things that control how the gene works e.g. how hard the gene will work, when the gene will work, therefore a gene from another organism will not automatically work it its placed in a different organism.

How living things appear and function depends on their phenotype – physical characteristics. This is caused by a combined effort of their coding – Genotype and the environment.

 The position occupied by the gene on the chromosome is the locus.

Most DNA looks like a double helix – the letters A T C G that exist on this helix are a particular code that makes up the basic units of DNA.

These building blocks are called nucleotides. Nucleotides are made up of 3 parts: Sugar, Phosphate and a Nitrogenous base. The sugar and phosphate stay the same but the nitrogenous base changes i.e. it could have any of the letters A T C G but it will still have sugar and a phosphate attached to it.

The rules:

ATCG always stands for: (they never change when attached to DNA)

  • A = Adenine
  • T = Thymine
  • C = Cytosine
  • G = Guanine

NB: A is always attracted to T and C is always attracted to G – this forms the rungs of the double helix model. A sequence of 3 nucleotides is called a triplet. Triplets code for particular amino acids.

Protein Synthesis

Protein Synthesis is the ability of DNA to make proteins, using the bases found on each of the DNA strands. The DNA unzips, copies itself, and sends codes to the ribosomes, where proteins are made. Here at the ribosomes the message is translated into amino acids which then make proteins.

Transcription is the process in which the unzipped DNA is copied by other free nucleotides.

Example:

The copy of DNA sequence is called messenger RNA. This message passes through the cytoplasm to the ribosomes where proteins are manufactured. RNA is not the same as DNA because thymine (T) is replaced by the base Uracil (U).

At the ribosomes the message is translated i.e. the amino acids are linked together in triplets to make specific proteins.

Amino Acids  Protein  Original DNA instructions.

Mitosis and Meiosis

Each kind of cell division involves chromosomes. What happens during this process is passed onto the next generation.

Mitosis: makes body cells e.g. stomach, skin, hair etc.

New body cells need to have the same amount of chromosomes every time during the replication process, so that a new cell has all the information the original cell had. The number of chromosomes in each body cell is called the diploid number. In normal body cells the chromosomes occur in pairs – 2n (diploid number). Therefore the diploid number of chromosomes in humans is: 2n = 2 × 23 = 46

image04.png

Meiosis – makes new human beings e.g. foetus  baby  adult

In sexually reproducing organisms such as humans gametes are produced in the sex organs – meiosis. During fertilisation the male gamete (sperm) fuses with the female gamete (ovum) to form the zygote – first cell in a human. Zygote = never identical to parents due to mixture of cells.

image05.png

1. The DNA replicates to form two chromatids. These then arrange themselves into homologous pairs (both coding for the same characteristics) and prepare for cell division.

4. The homologous pairs separate and go to opposite poles. For each of the 23 pairs there is a 50-50 chance as to which pole the paternal or maternal chromatids go.

5. The nucleus divides into two daughter cells each with a mixture of chromosomes.

6. The two daughter nuclei then divide to form two gametes in the same way as mitosis. The end result is four sex cells.

The Next Generation

Gregor Mendel and Austrian monk carried out experiments in a monastery garden for 17 years. He is known as the father of genetics. Mendel crossed a pure breed of tall plants with a pure breed of short plants. He showed that the shortness had not disappeared because ¼ of the plants were short. He called the shortness factor a recessive factor because it was hidden in the first generation.

Hybrid – a plant with both alternatives such as tallness and shortness for characteristics

Alleles – alternate forms for genes

Monohybrid cross – if only one trait is to be passed on to the next generation then it is a monohybrid cross.

Heredity – passing on characteristics and the study of how characteristics are inherited is called genetics.

If two alleles are the same i.e. AA (dominant pure) or aa (recessive pure) it is a homozygous gene. If they are different Aa (hybrid pure) then it is heterozygous.

Reginald Punnet (geneticist) invented the punnet square. Punnet squares allow us to work out which trait will be passed on, which is dominant and which is recessive.

NB: the ONLY way for a recessive trait to show up in an organism is if that organisms genotype is homozygous recessive (two little letters like “bb”)

Drawing a punnet square:

1. Determine genotypes of the parent organisms

2. Write down your cross (mating)

3. Draw a p-square

4. “Split” the letters of the genotype and them outside the punnet square

5. Determine the possible genotypes of the offspring by filling in the p square

6. Summarise the results

image06.png

Calculating Sex

Each human has 2 pairs of chromosomes, 22 of these are autosomes and the other one is the sex chromosome. Females have two X chromosomes and males have a X and Y chromosome.

Different animals have different sex chromosomes e.g. male birds have two Z chromosomes and female birds have Z and W sex chromosomes.

Twins – twins are born when clusters of cells form during the very early stages of cell division these clusters of cells eventually form two separate individuals hence twins are born. Usually only one ovum is released however if several are released twins or more can result from fertilisation by different sperm – if this happens they are not identical twins.

Certain types of disorders are called X-linked characteristics this because the recessive gene responsible for that particular disorder is carried on the X chromosome. As there is a greater chance of these types of disorders appearing in males it is often called a sex-linked disorder.

Mutations

Mutations are caused by an alteration to genes. Mutations can occure in a single gene – genetic mutation or in a chromosome –called a chromosomal mutation.

Mutations also include the number or the structure of chromosomes in the cells. Some mutations can be detrimental to the organism often causing death. Other mutations can be beneficial e.g. increases species diversity  increasing survival. (Galapagos Finches)

Mutations change characteristic by inserting a new base into a existing code. E.g. the original code may have coded for hair but when a mutation occurs it may change one of the bases e.g. changes the G in the code to a C – now the code codes for whole new protein maybe teeth.  

Mutagens – Factors that trigger a mutation in the cells.

Changes in the letter of a word can change the word’s entire meaning. Gene mutations  uncontrolled cell division which can result in cancerous tumours. Not all mutations are harmful i.e. for insects it is part of their survival mechanism.

Rate of mutations can be increased by exposure to high energy, radiation from X-Rays, nuclear radiation, chemicals and UV part of sunlight.

Mutations change genes using 3 methods, either by:

Deletion – letters in the chain of amino acids are deleted

Inversion – letters are swapped around

Insertion – letters are inserted into the chain

We don’t know what characteristics a baby will have its all random – in the same way getting a genetic disorder is also random. Eugenics is trying to improve the characteristics of human populations by selective breeding or genetic engineering.

Not all genes are turned on at the same time – some switched on later and can lead to late onset disorders such as Huntington’s disease.

Haemophilia – a mutation in one of the clotting factor genes. It is a sex linked disease which affects males of all ethnic backgrounds. People with haemophilia bleed longer because their blood does not clot well – can be treated with medicine – however they may suffer from internal bleeding in joints  painful arthritis.

Gene Technology

Gene Technology is the technology to take a single gene from a plant or animal cell and insert it into another plant or animal cell of a different species.

Transgenic – organisms whose gamete cells contain genetic material from another organism, or contains genetic material that has been altered in some way.

Agriculture – gene technology can be used in agriculture and food production to:

  • Increase crop or animal resistance to pests – reducing the use of chemicals
  • Increase crop or animal tolerance to chemicals
  • Create disease resistant crops and animals
  • Improve the food yield per plant or animal
  • Make plants and animals mire suited special environmental conditions such as drier regions or saline water
  • Improve the nutritional quality of food produced by the plant or animal.

Food – genetically modified food has become a major source of debate during the past 10 years. It is always up to personal opinion to wether eating genetically modified foods is right or wrong.

Medicine – Recombinant DNA is used to produce human insulin to help those suffering from diabetes. Immune reactions were common to the extracted pig insulin. Now the production of insulin comes from the human gene which can be inserted into the plasmids, rings of DNA, of bacteria.

Researches looking at a way to produce vaccines that are edible meaning vaccination programs are as easy as eating a piece of fruit or vegetable. Worried about these getting into our food markets so they focusing on making vaccines edible in the leaves of plants that are not available on sale.

DNA vaccines – instead of stimulating the body’s immune system using the pathogen itself, DNA vaccines use its genetics

Advantages of this include:

  • Purity – made artificially so the vaccine is much purer
  • Specificity – the vaccine only contains one of the many genes necessary for the pathogen to reproduce – it’s enough for the immune system to recognise as foreign but not enough for it to make you sick.  
  • Makes it possible to vaccinate against variants of that disease as well not just one strain
  • Cost and ease of storage – cheap to make and doesn’t require refrigeration and can be stored for a long time

This student written piece of work is one of many that can be found in our GCSE Classifying Materials section.

(?)
Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Related GCSE Science Skills and Knowledge Essays

See our best essays

Related GCSE Classifying Materials essays

  1. Marked by a teacher

    Chemistry revision notes. Atomic Structure and Bonding, Electrolysis, Acids and Alkalis.

    5 star(s)

    the maximum mass of alcohol which could be obtained by fermenting some sugar is 4.6g of alcohol. The actual mass obtained in an experiment was 3.5g. Find the % yield. Answer = 3.5 x 100 = 76.1% 4.6 Rates of Reaction (F)

  2. Marked by a teacher

    Identifying an Ionic Compound. Objectives: To learn and test for metal ions ...

    5 star(s)

    This meant that the litmus paper had been exposed to an alkaline source and so there was a basic solution because the pH greater than 7 (pH of 9). The last test was the flame test for Na+, K+, Ca2+, Cu2+ where dilute hydrochloric acid and heat were applied.

  1. Marked by a teacher

    The Periodic Table - Revision Notes The numbers in italics are the page numbers ...

    5 star(s)

    to make an acidic oxide. 68 Eg. Sulphur + Oxygen Sulphur Dioxide S + O2 SO2 All metal elements burn in oxygen to make basic (alkaline ) oxides. Eg Sodium + Oxygen Sodium oxide 4 Na + O2 2 Na2O Groups and Periods 56 A horizontal line going across the periodic table is called a period of elements.

  2. Marked by a teacher

    Chemistry Revision Notes on atomic structure, nuclear power and the periodic table

    4 star(s)

    All protons have a single positive electric charge. A neutron however is an uncharged particle where as the nucleus contains only protons and neutrons, the positive charge of the protons prevails in the nucleus. > The electric charge on an electron is exactly equal and opposite of that on a proton.

  1. Marked by a teacher

    In this CDA I will write about how plastic bags are made, why plastic ...

    There are also many disadvantages of plastic bags. The United Nations discovered in 2006 that 'Ten percent of the plastic produced every year worldwide winds up in the ocean. 70% of which finds its way to the ocean floor, where it will likely never degrade.'

  2. Rate of reaction of hydrochloric acid on magnesium.

    The actual experiment: The 5 different concentrations of hydrochloric acid I will be using in my experiment are, 0.3M, O.4M, 0.5M, 0.6M and 0.7M. I will achieve these concentrations by diluting 1M of HCl with water. I will have my weakest concentration to be 0.3M because the reaction would not

  1. Reactions of period 3 elements with Oxygen, water and chlorine.

    + Cl2 (g) --> PCl5(s) this reaction is a equilibrium in a closed system. S Reacts on heating to give pale-yellow covalent liquid. 2S(S) + Cl2(g) --> S2Cl2(s) Reactions with "COLD" Water: Na Violent reaction at room temperature; metal melts and rushes about on the surface of the water; hydrogen evolved, product solution alkaline.

  2. Identification of an unknown compound.

    All the evidence from the NMR, infrared and mass spectrum suggests that compound B is the aldehyde ethanal. Several limitations of the provided spectra are described below. NMR: Evidence from the NMR spectrum in particular show that compound B is ethanal.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work