UK GCSE level age ~14-16, ~US grades 9-10 Biology revision notes re-edit 12/05/2023 [SEARCH]

 Genome: 2. The importance of genome knowledge - the human genome project

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INDEX of biology notes on the human genome

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(2) The importance of genome knowledge - the human genome project

The genome is the term that describes the total genetic material of an organism - all the DNA.

The human genome projects has mapped and identified all the genes found in human DNA.

Every organism has its own unique genome and scientists can now completely work it out - clever stuff!

Genome data is used to characterise species and help research plant and animal evolution patterns.

See note 3. below on the human genome.

The human genome has around 3 billion base pairs in the DNA sequences of the genes-chromosomes!

Apparently quite a lot of your DNA is 'junk', but don't worry, and we won't go into that, just study hard, play hard and enjoy life!

Thousands of scientists around the world have collaborated on the human genome project.

We now know the complete human genome and over 20,000 to 25,000 genes have been located on it, but although we know what many do (code for), there is much more to find out.

Around 1800 genes have been identified that relate to human diseases - and this data is the target of medical research to benefit medicine.

PLEASE NOTE that all humans share 99.9% of their genomes, which makes you think!

 

How is our understanding of the human genome helping science

e.g. evolution theory or medicine?

Any new drug must be targeted at some specific medical condition where there is a need.

The target might be blocking the action of an enzyme or a gene with a chemical agent (drug) you can interfere with the development of a disease e.g. the anti-cancer drugs used in chemotherapy treatments to reduce the growth of tumour cells or kill them.

Studies of the genomes and resulting proteins in both plants and animals are proving useful to identify 'targets'.

You then have to find a chemical that will have an effect on the target, fortunately there are databases of chemicals that have been previously screened for likely effectiveness.

The screening might not initially indicate the best molecule to 'hit the target' in a biochemical sense, but, it may provide a starter molecule - which you can then modify to make different derivative molecules, one of which might provide a more effective treatment.

Medical applications

e.g. prediction and prevention of disease, testing for and treating inherited diseases, more effective medicines, BUT, there are ethical issues to deal with too.

1. It has been possible for genetic scientists to identify particular genes (genetic variants) in the genome that are linked to certain types of non-inherited diseases.

Hopefully it will lead to predicting predisposition to certain diseases, leading to early intervention with medical treatment and perhaps a preventing disease actually developing.

If you know what genes predispose people to certain diseases, medical advice can be more accurately given e.g. choice of diet and other lifestyle factors based on the results of genetic screening tests.

Many common diseases like cancer and heart conditions are caused by the interaction of different genes, as well as lifestyle factors.

See also Introduction to genetic variation - formation and consequence of mutations 

and Stem cells and uses - leukaemia treatment

 

2. From the human genome project, by knowing the genes associated with an inherited disease (genetic disorder), we can understand it more clearly and then develop more effective treatments - which may involve genetic engineering itself.

We know inheriting certain genes greatly increase your risk of developing certain cancers, this can help with making lifestyle choices to minimise the risk of suffering from the disease - as with 1. above, its a sort of risk management situation.

In the UK newborn babies are routinely tested for particular genetic variants known to cause genetic disorders e.g. the double recessive allele that causes cystic fibrosis.

The results from genetic screening enables the medical treatment-management to begin promptly while the baby is still very young.

Children with leukaemia can have a genetic test to help decide which is the most effective treatment in terms of medication and its dose.

See further notes on genetic screening of an embryos or fetus

and Introduction to the inheritance of characteristics and inherited disorders

It is hoped that all this new genetic science will lead to the development of better, and more personal, treatments for a wide range of medical conditions.

We are now developing drugs and other techniques that work at the molecular level in combating disease and tailored to suit the individual's body chemistry.

The variations in patients genetic variants (alleles) mean that one drug isn't necessarily as effective with all patients suffering from the same condition - so new drugs can be designed to suit these 'varying' patient situations.

3. We know certain alleles affect how our body responds to certain diseases and their treatment.

Scientists hope to use this knowledge to develop more effective drugs that can be specifically suited to patients with certain alleles in their genome.

Different drugs can be tested, and their effectiveness compared with the patient's alleles, and you can compare existing drugs with new ones.

It has been found that some breast cancer drugs are only effective in women if they have certain alleles in their genome.

4. To help in these medical quests, scientists are analysing the genomes of human pathogens to help us understand and control certain infectious diseases.

The complete genome of bacteria such as the deadly MRSA, which is resistant to antibiotics.

It is hoped that pathogen genome knowledge will allow swifter decisions as to the best treatment administered to patients i.e. determined by the genomics of the specific bacterial strain.

 

The science of human evolution and migration

The human genome project can be tackled by various genetic strategies.

(i) Analysis of data from people's Y chromosome inherited down the male line.

(ii) Analysing mitochondrial DNA inherited through mothers.

Our knowledge of the human genome is being used to trace the migration of certain populations across the continents of the world.

The latest research suggests that all modern humans have descended from a common ancestor who lived in Africa, and their descendents have spread over all over the Earth - moving by both land and sea.

This is known as the 'Out of Africa' theory and seems to have begun around 60 000 years ago.

Why did this happen?

Maybe change in climate, so seeking more food for hunter-gathering tribes?

It is known the climate in Africa at this time became much dryer - less rain, less plant life, less food for animals, less plants and animals for humans to eat.

All humans have a very similar genome.

In terms of ancestors - genetically, who you were and where you have been is 'hidden' in your genome! until, that is, modern DNA analysis reveals all !!!

However, as different populations of people migrated to different areas of the planet, small differences in DNA 'evolved' (incorporated) into their genome e.g. producing different skin or hair colour or facial features.

The genetic variation is as little as 0.001%, but even so, genetic scientists can work out when these new populations split off in a different 'genetic' and geographical direction.

People who are related will have an even more similar genome.

The human genome is being compared to some of closest relative in the world e.g. primates.

Ever since researchers sequenced the chimp genome in 2005, they have known that humans share about 99% of our DNA with chimpanzees, making them our closest living relatives - that should make you think!


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