Introduction
Chromosomes and genes
Chromosomes, found in the cell nucleus, contain many genes. A gene is a section of DNA, which carries coding for a particular protein. Different genes control the development of different characteristics of an organism. Many genes are needed to carry all the genetic information for a whole organism.
Chromosomes, found in the cell nucleus, contain many genes. A gene is a section of DNA, which carries coding for a particular protein. Different genes control the development of different characteristics of an organism. Many genes are needed to carry all the genetic information for a whole organism.
Human Genes
The number of genes and chromosomes varies from species to species. For example, cells in human beings have 46 chromosomes that carry about 30,000 genes in each cell; and cells in fruit flies have 8 chromosomes that carry about 13,600 genes.
Always in Pairs
As you can see above, each of our chromosomes has a matching one. it is the same length and has the same genes. They are known as a homologous (hom-ol-og-us) pair.
One of the pair is a copy of a chromosome that came from your mother, the other came from your father.
It is useful to have two of each gene because if one does not work properly for some reason, the other takes over the job. We have lots of faults in out DNA but most of the time they present no problem.
The thing is, although we have 2 of each gene they are not always exactly the same. For example you have two genes telling the cells of your eyes to make a protein that gives them colour. However, the gene from your mum may be saying to have green eyes, while the gene from your dad is saying to have blue. We call the different forms of the same gene alleles. (al-eels)
One of the pair is a copy of a chromosome that came from your mother, the other came from your father.
It is useful to have two of each gene because if one does not work properly for some reason, the other takes over the job. We have lots of faults in out DNA but most of the time they present no problem.
The thing is, although we have 2 of each gene they are not always exactly the same. For example you have two genes telling the cells of your eyes to make a protein that gives them colour. However, the gene from your mum may be saying to have green eyes, while the gene from your dad is saying to have blue. We call the different forms of the same gene alleles. (al-eels)
Amazing facts about DNA
There are lots of facts about DNA, but here are 10 that are particularly interesting, important, or fun.
- Even though it codes for all the information that makes up an organism, DNA is built using only four building blocks, the nucleotides adenine, guanine, thymine, and cytosine.
- Every human being shares 99% of their DNA with every other human.
- If you put all the DNA molecules in your body end to end, the DNA would reach from the Earth to the Sun and back over 600 times (100 trillion times six feet divided by 92 million miles).
- A parent and child share 99.5% of the same DNA.
- You have 98% of your DNA in common with a chimpanzee.
- If you could type 60 words per minute, eight hours a day, it would take approximately 50 years to type the human genome.
- DNA is a fragile molecule. About a thousand times a day, something happens to it to cause errors. This could include errors during transcription, damage from ultraviolet light, or any of a host of other activities. There are many repair mechanisms, but some damage isn't repaired. This means you carry mutations! Some of the mutations cause no harm, a few are helpful, while others can cause diseases, such as cancer.
- Scientists at Cambridge University believe humans have DNA in common with the mud worm and that it is the closest invertebrate genetic relative to us. In other words, you have more in common, genetically speaking, with a mud worm than you do with a spider or octopus or cockroach.
- Humans and cabbage share about 40-50% common DNA.
- Friedrich Miescher discovered DNA in 1869, although scientists did not understand DNA was the genetic material in cells until 1943. Prior to that time, it was widely believe that proteins stored genetic information.
Interested?
You can find out more by looking at the A-level pages - just don't go getting yourself confused!