D1.3 - mutations and gene editing

Question 1

somatic

Answer 1

of the body

Question 2

What is a gene mutation?

Answer 2

structural changes to genes at a molecular level which change the base sequence of DNA

Question 3

What are the 3 types of gene mutation?

Answer 3

1. Substitutions
2. Insertion
3. Deletions

Question 4

What is a substitution?

Answer 4

where one base is replaced with another base

Question 5

What is an insertion?

Answer 5

where a base is added to a gene

Question 6

What is a deletion?

Answer 6

where a base is removed from a gene

Question 7

What is a SNP?

Answer 7

single-nucleotide polymorphism

Question 8

Which type of mutation forms a SNP?

Answer 8

base substitution reactions

Question 9

What are the consequences of base substitutions on the process of protein synthesis?

Answer 9

1. Template strand of DNA will have a different triplet.
2. Different codon produced within the mRNA molecule.
3. Different tRNA will bind to the modified mRNA.
4. Different amino acid may be incorporated into the polypeptide chain.
5. Polypeptide could fold into a different shape with a different function.

Question 10

What is a missense mutation?

Answer 10

a change in amino acid causes a different protein to be made during translation

Question 11

What is a silent mutation?

Answer 11

due to degeneracy of the genetic code, mutation may or may not change a single amino acid in the polypeptide

Question 12

What is a nonsense mutation?

Answer 12

if a stop codon was generated in the base substitution, the protein made is truncated (cut short)

Question 13

Why is the amino acid change not guaranteed following a base substitution reaction?

Answer 13

the degeneracy of the genetic code means that more than one codon codes for a particular amino acid

Question 14

What are 3 causes of gene mutation?

Answer 14

1. Chemical mutagens such as benzene or polystyrene
2. Mutagenic forms of radiation such as UV light and radium
3. Errors in DNA replication or repair

Question 15

What is the randomness of mutations?

Answer 15

• mutations can occur anywhere in a base sequence of a genome, but some bases such as CpG sites have a higher probability of mutation than others
• no natural mechanism is known for making a deliberate change to particular bases with the purpose of changing a trait

Question 16

Where do most mutations occur and what is the impact?

Answer 16

• most mutations occur in non-coding regions which can impact the gene expression or disrupt functional roles of DNA

Question 17

What are the 2 outcomes of insertion and deletion mutations?

Answer 17

There is a likelihood of polypeptides ceasing to function due to :
1) Frameshifts - deletion or insertion of 1 or 2 bases results in all codons being modified, resulting in amino acid changes.
2) Major insertions or deletions - if sections of many amino acids are added to or removed from the protein, the 3D shape and it’s function will change.

Question 18

In what circumstances would an insertion or deletion not cause a frameshift mutation?

Answer 18

• If base insertions or base deletions occur in multiples of 3; causing discrete amino acids to be added or removed.

Question 19

What is a germ cell?

Answer 19

Germ cells use meiosis to produce gametes for sexual reproduction.

Question 20

What are somatic cells?

Answer 20

Somatic cells use mitosis to divide and provide cells for tissue and organs within the body.

Question 21

What can occur of the mutations in the somatic cell DNA mean the process of mitosis becomes uncontrolled?

Answer 21

Mutations in somatic cells are associated with cancer and the formation of tumors. The mutation will be found in the DNA of all cells of the tumor.

Question 22

What are the consequences of mutation in germ cells?

Answer 22

Mutated genes are passed onto the gametes and inherited by the next generation (or organism).

Question 23

What are the consequences of mutation in somatic cells?

Answer 23

Mutations in somatic cells are not passed on to the next generation or organism.

Question 24

What is the role of SNP’s in genetic variation?

Answer 24

The formation of single-nucleotide polymorphism causes new alleles to be formed.

Question 25

What is the impact of most mutations for an individual?

Answer 25

Most mutations are either harmful or neutral for an individual organism.

Question 26

Why are mutations essential at a species level in the long-term?

Answer 26

Mutations are essential in the long-term for evolution by natural selection.

Question 27

What is the role of mutation as a source of genetic variation?

Answer 27

• Genetic mutation is the source of all genetic variation

Question 28

What is the process of evolution by natural selection?

Answer 28

1. Mutations form new alleles and cause variation amongst organisms of the same species.
2. Some mutations make organisms more suited to the environment.
3. Individuals that are better adapted survive and reproduce to produce offspring.
4. Individuals pass on mutation to their offspring.
5. Natural selection increases the frequency of characteristics and therefore alleles that make individuals better adapted to the environment.