• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Inherited sources of genetic variation.

Extracts from this document...


Inherited sources of genetic variation One of the key features of all living things from single celled organisms such as amoeba, to plants and animals such as humans, is the ability to reproduce. In smaller single celled organisms such as the amoeba this reproduction is asexual and takes place by a process known as mitosis. Mitosis produces two daughter cells that are genetically identical to, or clones of their parent cell. This process however produces no genetic variation within a community; meaning that the process of evolution is limited and can only take place through an advantageous mutation over a long period of time. Mitosis also produces somatic, or body cells for growth and repair in multi-cellular organisms. To increase genetic variation other larger and more complex organisms such as plants and animals reproduce sexually by Meiosis. ...read more.


It is this random shuffling process that creates a huge variety of gametes from a single parent. Recombination occurs when pieces of chromosomes are exchanged within their homologous pair. This increases the swapping of genetic information leading to more genetic variation. Crossing over only occurs in the first division of meiosis, this is when whole groups of genes are mutually exchanged between the homologous chromosomes. The other factor allowing genetic variation to take place is mate selection. Variation is furthered by the ability of an individual to choose a mate with which to produce offspring. Different combinations of genes will come together in the offspring during fertilisation, depending on which two individuals mate. Mutations also cause variation, as they are the source of all new genetic information. Whilst most mutations are harmful, there are others that are described as 'silent' this means that these mutations have no known effect on the individual, and some can provide an improvement on the original version of the gene. ...read more.


This is caused by a point mutation which is located on the HBB gene on chromosome 11 and involves the substitution of one base for another this alters a single amino acid. This new amino acid makes the haemoglobin behave in a different manner as it has different properties. One other inherited disorder is Down syndrome, which is caused by Trisomy. This is when three chromosomes represent one chromosome pair. The mutation for Down syndrome occurs on chromosome 21, the most common form of this condition arises when meiosis fails to separate the pair of chromosome 21 in female ova. One in 800 babies born to mothers aged 30 to31 have Down syndrome, however this increases rapidly with the mothers age. Some of the symptoms include poor muscle tone, congenital heart disease and mental retardation. Jessica Jennings 13 Kee ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Genetics, Evolution & Biodiversity section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

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

See related essaysSee related essays

Related AS and A Level Genetics, Evolution & Biodiversity essays

  1. Marked by a teacher

    An Investigation into the Mitotic Nuclear Division of Allium Sativum Root Tip Cells, and ...

    5 star(s)

    of chromosomes at the centromere to form individual chromatids, and their assisted movement to the poles of the cell. These processes are more electrochemical in nature than biological, as this movement occurs due to the interactions of a "motor protein", kinesin, which utilises the charged nature of the microtubule to

  2. The Biology of Autistic Spectrum Disorder and the Social Implications

    The parent also added that 'the fundamental issues relating to communication, behaviour and language disorder, Continue to be misinterpreted as "bad behaviour," and "not listening". It could be that teachers are not trained to recognise that bad behaviour could be a result of ASD as disruptiveness is a common symptom.

  1. Recombinant DNA, genetically engineered DNA prepared in vitro by cutting up DNA molecules and ...

    If one copy of the gene is normal, the risks of breast and ovarian cancer are lower. Two different research teams found that the normal function of both genes is to produce proteins that help repair breaks in chromosomes, which contain DNA.

  2. Mitosis and Meiosis

    o) Meiosis occurs in, if you are male, the testes. If you are female, these are the ovaries. p) In plants, meiosis occurs in, the male sex organs, the anthers and the female gonad is the ovary. 5. q)

  1. Cell Theory - Discuss the theory that living organisms are composed of cells.

    Mutation: GAA --> GTA Transcription: CUU --> CAU Translation: valine-->glutamic acid Result: HbA --> HbS (Sickle Cell Anemia) 3.2 Meiosis (2h) 3.2.1 State that meiosis is a reduction division in terms of diploid and haploid numbers of chromosomes. Meiosis: reduction division from diploid to haploid number of chromosomes 3.2.2 Define homologous chromosome.

  2. What different methods exist for studying genetic variation at a molecular level? How could ...

    has been cultivated. An example of such a situation is shown below, where an SNP consists of a T-A nucleotide pair in one DNA molecule and a C-G pair in another molecule. The selected restriction endonuclease, EcoR1, will cut in the middle of a palindromic site reading 5'-GAATTC-3.'

  1. Colour variation in Littorina littoralis on the upper, middle and lower zones of a ...

    Although this is not the case, this provides a rough idea of how I will expect the Littorina littoralis to be distributed. Being submerged by the sea can also help species hide from terrestrial predators. Predation is an important biotic factor on rocky shores especially for Littorina littoralis, whose only defence mechanism is its shell.

  2. Investigating the colour variation of Littorina littoralis and their abundance across the upper, middle ...

    Exposure to sunlight and air causes increased rates of evaporation. For the Littorina littoralis, prolonged exposure to these conditions can cause them to dry out, known as desiccation. For this reason, it would be unlikely for any Littorina littoralis to be permanently situated in the upper zone, or indeed for

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