Investigating the Function of Individual Genes

Question 1

How do we get information about the function of a gene from its phenotype?

Answer 1

By studying organisms that are naturally mutant for a particular gene, we can work out what a gene might fo

Question 2

What do we do when no natural mutants exist?

Answer 2

Make our own

Question 3

What can we learn from studying natural and our own mutants?

Answer 3

How particular mutations lead to phenotypic changes

Question 4

What happens within natural mutants?

Answer 4

Genetic change (mutation) alters the phenotype

Question 5

What does natural mutants do?

Answer 5

Give us clues to gene function

Question 6

What is conserved in other animals?

Answer 6

Many of the human genes which have unknown functions still

Question 7

How many human genes still have unknown function?

Answer 7

Around 4500 (23%)

Question 8

What can we do to the genes which animals and humans have in common?

Answer 8

Create mutants of them and then we may learn of their functions in humans

Question 9

What do we study when using genetic techniques to find out what a gene does?

Answer 9

Organisms that are naturally mutant for the gene (rare)

Question 10

What can we increase to find out what a gene does?

Answer 10

The rate of random mutation, select for a phenotype of interest and sequence the genome to identify the mutation (genetic screen)

Question 11

What can you do with genes to find out what it does?

Answer 11

Take the gene you are interested in, copy it and insert it into another organism (transgenesis/genetic engineering)

Question 12

What can you deliberately do to a gene to find out what it does?

Answer 12

Break a particular gene to find out what happens (targeted mutation/gene knockout/reverse genetics)

Question 13

What is the approach called when using genetic techniques to find out what a gene does?

Answer 13

Functional molecular genetics

Question 14

What do share with animals?

Answer 14

Many of our genes

Question 15

What are model organisms?

Answer 15

Ones that can easily be raised in a controlled environment and are easy to manipulate genetically

Question 16

What does each organism have?

Answer 16

A different approach that works best for making changes to the DNA genome

Question 17

How can mutants be made?

Answer 17

By treatment of gametes with mutagens such as x-rays or chemicals

Question 18

What are mutations made by treatment of gametes with mutagens such as x-rays or chemicals?

Answer 18

Random and can give quite dramatic phenotypes

Question 19

What is the DNA code?

Answer 19

Universal

Question 20

What is meant by the DNA code being universal?

Answer 20

Any DNA can be used by any organism and interpreted by any cell- even synthetic DNA

Question 21

What is transgenesis?

Answer 21

Engineering a multicellular organism by adding in “foreign” DNA

Question 22

What can we use transgenic DNA for?

Answer 22

To understand how genes work, to engineer recombinant proteins (synthetic biology), or in gene therapy approaches

Question 23

How does transgenesis occur?

Answer 23

A fertilised embryo is held by a pipette and the DNA from the transgender is added through the zone and cell membrane into the male pronucleus hoping it will get integrated into the chromosomal DNA of the organism. The embryo is then inserted into the organism and left to process

Question 24

How do we know if a gene variant is pathogenic?

Answer 24

Modern genetics targets mutations to the DNA sequence of your choice to “break” specific genes

Question 25

How can we damage or modify the gene we are interested in?

Answer 25

By genetically modifying an organism or cell line

Question 26

What can we do by examining the organism or its offspring?

Answer 26

We should be able to work out what the gene normally does

Question 27

Where did the Cas9 protein come from?

Answer 27

It evolved in bacteria for an antiviral defense

Question 28

What needs to be decided in CRISPR-Cas9?

Answer 28

Which gene you wish to mutate

Question 29

What do you do once you have decided which gene you want to mutate?

Answer 29

Design a short "guide" RNA that only binds to your gene of interest and combine this with the Cas9 protein to make a Cas9-guide RNA complex

Question 30

What do you do with the Cas9-guide RNA complex?

Answer 30

Get it into the cells of interest in the model organism which is not as easy as it seems

Question 31

What happens once the Cas9-guide RNA complex is in the cells of interest in the model organism?

Answer 31

Cas9 enters the nucleus and finds the target sequence in the genome that match guide RNA

Question 32

What does Cas9 do once it has entered the nucleus?

Answer 32

It makes a double stranded break in DNA at the target site

Question 33

What happens once Cas9 makes a double stranded break in DNA at the target site (in the absence of a template)?

Answer 33

DNA repair enzymes try to patch up the cut which often results in errors as there is no template to read from. Small indels are created at the target site, the gene is potentially disrupted or mutated

Question 34

What happens once Cas9 makes a double stranded break in DNA at the target site (in the presence of a template)?

Answer 34

It is possible to use the repair template to edit the DNA sequence at the cut site (gene editing)

Question 35

Can we fix a genetic disease?

Answer 35

Yes we can but only if we know what causes it, have a way to correct the defect and have considered ethics

Question 36

How are somatic genetic diseases fixed?

Answer 36

The cells or organs affected are targeted which does not affect the next generation as it is not a change to the germline

Question 37

How may gremlin genetic diseases be fixed?

Answer 37

Pre-implantation genetic diagnosis, Three parent babies or CRISPR "gene" edited babies

Question 38

What is involved in pre-implantation genetic diagnosis?

Answer 38

In families with an identified risk, IVF can be used to make embryos from the parents eggs and sperm. These embryos can be tested before implantation and only healthy embryos implanted

Question 39

What is the faulty gene in three parent babies?

Answer 39

The faulty gene is on the mitochondrial DNA

Question 40

How are three parent babies formed?

Answer 40

The nucleus from the fertilised egg of the parents which contains the mitochondrial disease is removed and transplanted into a donor egg which contains good mitochondria and has had the nucleus destroyed

Question 41

What is the composition of the embryo of three parent babies?

Answer 41

Nuclear DNA from biological parents and mitochondrial DNA from the donor