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Chromosomes and Life Cycles

Satisfactory Essays
Chromosomes and Life Cycles

Chromosome Structure

All cells contain a nucleus that has a membrane around it. Inside the

nucleus are chromosomes. The chromosomes are made from a molecule

called deoxyribonucleic acid - which is commonly known as DNA. DNA is

a very long molecule, so long in fact that the DNA from just one

person is long enough to stretch all the way to the moon. Reading this

it would be hard to understand how DNA could fit into our cells, but

this problem is overcome due to it being highly coiled to make it much

shorter, and is also divided into lengths called chromosomes.

DNA has two jobs to do - 1) It must store information, this would

account for why the DNA molecule has to be so long, as it has to store

a phenomenal amount, and 2) It must be able to copy itself so that

this information can be passed on to the next generation. It is

important that the DNA can make an exact copy of itself with as few

mistakes as possible so that problems will not occur due to faulty

genes in the next generation.

[IMAGE]

A simplified picture of DNA is shown above.

The DNA is divided into sections called genes. Each gene contains all

the information for a single instruction. This instruction is how to

make a single protein, which is produced in the cells cytoplasm. The

body uses the different proteins produced by the genes in many

different ways. Every cell in your body contains about 40,000

different genes. All this may be more easily understood by reading the

next statement,

'If all the chromosomes in a nucleus are represented by a book, and

each chromosome is represented by a chapter, then each gene would

represent a single letter.'

From species to species the number of chromosomes varies. In humans

there are normally 46 chromosomes. However on rare occasions there can

be more than this, but it always leads to health problems. An extra
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