Discuss human chromosome and try to explain their structure and functions in human body and in part 2 we look at a genetic disorder, sickle cell anemia.

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Biology Assignment

Name: Behrooz Khoshooee

Student Number: 283644

Biology, November 2005

Introduction:

This paper has two parts, in part one we discuss about human chromosome and try to explain their structure and functions in human body and in second part we look at a genetic disorder, sickle cell anemia. We will investigate what affect it has in human body and how one person could get this genetic disorder.

Part 1

Nucleus

Nucleus contains the DNA in chromosomes and therefore it is the primary source of information for controlling the metabolism, reproduction of cell and inheritance. Using a microscope we could see a dark network in nucleus which is called chromatin. Chromatin consists of a complex of DNA coated in protein, which during cell division it becomes structured and turn into separate packages of chromosomes (Czepulkowski 2001).

(1) Nuclear envelope (2) Ribosomes (3) Nuclear pore complexes (4) Nucleolus (5) Chromatin (6) Nucleus (7) Endoplasmic reticulum (8) Nucleoplasm

Chromosome

The number of chromosomes is always the same in each type of species i.e. in human cells there are 46 chromosomes and it would be same for everyone.

Because chromosomes are paired, the possibility of having an odd number of chromosomes is zero, so chromosomes number is always an even number. The chromosomes pairs are called homologous pairs which means similar in structure, one from each parent (Murray 2001).

In cell division chromosomes replicates it self and the identical structures are called chromatids. While chromosomes replicate themselves the main goal is to replicate the DNA which we will go in to more details (Murray 2001).

Human Chromosomes

Structure of chromosome

Deoxyribonucleic acid and ribonucleic acid

Nucleic acid is very important as they play a major role in releasing and storage of energy and more importantly they are involved in determination and transmission of genetic characteristic. If we separate nucleic acid from protein, we will discover that nucleic acid is build of component called nucleotide. These components are made of sugar, a phosphate group and a nitrogen-containing protein. There are two type of sugar in these unit, ribose or deoxyribose when one oxygen atom is missing, and both have 5 carbons. This would result into having two types of nucleic acid, Deoxyribonucleic acid/DNA and ribonucleic acid/RNA. The genetic information is stored in DNA; the sequences of DNA will be used as template for production of RNA. And the RNA will be used as template for producing the protein polypeptide (Czepulkowski 2001).

In nucleotide, Nitrogen-containing part is the most changeable part. We could separate them into two main different types according to whether they have one or two carbon-nitrogen ring. If they have one carbon ring they are called “pyrimidines” and if they have two carbon rings are called “purines”. In DNA and RNA there two main types of purines, Adenine (A) and Guanine (G); but when it comes to pyrimidines DNA and RNA have different types of pyrimidines. In DNA we have Cytosine (C) and Thymine (T) and in RNA we have Cytosine (C) and Uracil (U) instead of thymine. Nitrogen-containing element is known as base as well (Czepulkowski 2001).

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It was in 1953 when Watson and Crick proposed the double-stranded structure for the DNA molecules and it was soon accepted by everyone. They proposed that double-stranded structure has free ends which would enable it to separate the complementary strand. The two complementary strands are hold together by a series of week hydrogen bonds. This bond is between the bases of each strand. In DNA A always bonds with T and C bonds with G (Czepulkowski 2001).

To have the long strand of DNA we need bonds between the carbon atoms in consecutive sugars. These bonds are called ...

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