HUMAN MOLECULAR GENETICS SHIT THAT I HAVE TO KNOW :(

Question 1

Why was the human genome sequenced? (5)

Answer 1

1. to identify all genes and their roles
2. analyse genetic variation between humans as a species
3. to be able to sequence the genomes of model organisms used in genetics such as the fruit fly
4. develop new sequencing techniques and computational analysis
5. share genome information with the public

Question 2

What are the reasons for analysing genetic variation within the human genome? (6)

Answer 2

1. discover who you are related to
2. determine where some of your ancestors come from
3. muscle types
4. risk of disease
5. drug metabolism
6. crime solving

Question 3

Explain why polygenic genetic disorders are usually probabilistic, not deterministic, and provide ONE example.

Answer 3

Most diseases arise through a combination of genetic variants (DNA changes), and interaction with the environment. This means that having a disease-related variation does not mean that you will get the disease, therefore is probabilistic.
eg. cancer, diabetes, multiple sclerosis

Question 4

What is triplet repeat expansion?

Answer 4

An error where triplets become massively expanded creating a repeated cluster of three nucleotides. e.g. Huntington’s disease CAG

Question 5

Outline the process of transgenesis

Answer 5

‘Foreign’ DNA (containing gene of interest) is injected into the male pronucleus of the fertilised mouse egg. Eggs are then transplanted back into the female for embryos to develop, and a litter is born. Successful transgenic mice contain an extra piece of DNA and can express the protein e.g. the transgenic jellyfish green fluorescent protein

Question 6

What is an STR?

Answer 6

repeats of 2-5 nucleotides found in specific regions of the genome where the number of repeats varies.

Question 7

What are CNVs?

Answer 7

large areas of DNA >500bp that are present in different amounts person to person (large portions that have been duplicated or deleted compared to the human reference genome).

Question 8

What is gene therapy?

Answer 8

We can use a virus to deliver a good copy of a gene into the stem cells and then the descendants of the stem cells will all be fixed.

Question 9

How do we know if a gene variant is pathogenic?

Answer 9

By damaging a gene we are interested in to work out what the gene normally does

Question 10

CRISPR is one way to test if a gene is pathogenic. Explain how it works

Answer 10

• Cas9 protein contrains active sites that can cut DNA
• a guide RNA binds with the Cas9 protein forming a complex that is allowed to then be introduced into the cell
• In the nucleus, the complementary sequence of the RNA binds to part of the target gene
• the active site of the Cas 9 protein cut the DNA on both strands
• this results in a cut in the target gene
• the broken strands of DNA are “repaired” by the the cell in two different ways

Question 11

Why is transgenesis useful? (4)

Answer 11

• To understand how genes work / what a gene does.
• To engineer useful protein products (synthetic biology).
• For gene therapy approaches.
• To study the effect of making a foreign protein or of making a protein in the wrong cells.