D1.3 Mutation and Gene Editing

Question 1

Define mutation.

Answer 1

Change in the DNA base sequence

Question 2

Distinguish between base substitution, insertion and deletion mutations.​

Answer 2

Base substitution mutation occur when one or more nucleotides in a DNA sequence is replaced by another nucleotide
Insertion mutation occur when one or more nucleotides is added to a base sequence
Deletion mutation occur when one or more nucleotides are removed from a DNA sequence

Question 3

Define single- nucleotide polymorphism.

Answer 3

Single nucleotide base substitution that leads to two different phenotypes within a population

Question 4

Outline the impact of genetic code degeneracy on the effect of mutations.

Answer 4

If genetic code is degenerate then AA can be coded by more than one codon. A base substitution doesn’t affect the protein if mutated codon codes for the same AA in a protein. If base substitution mutation mutates a codon to code for a different AA then a different protein sequence is produced.

Question 5

Distinguish between same-sense, nonsense and mis-sense base substitution mutations.

Answer 5

Same sense mutation : doesn’t alter the AA sequence
Nonsense mutation : base substitution creates premature stop codon
Missense mutation : base substitution creates codon that codes for different AA

Question 6

Define “frameshift” mutation.

Answer 6

Results from insertions or deletions of nucleotides and changes all codons after the mutation

Question 7

Outline the consequences of insertions and deletions on polypeptide structure and function.

Answer 7

All codons after insertion and deletion are changed which completely changes the sequence of AAs the polypeptide will have a different shape and won’t be able to carry out its function.

Question 8

Outline causes of gene mutation.

Answer 8

Errors in DNA replication or during repair of damaged DNA

Question 9

Define mutagen.​

Answer 9

Agents that cause permanent heritable changes to the DNA of cells

Question 10

Distinguish between germ cells and somatic cells.

Answer 10

Germ cells develop into gametes such as sperm or eggs
Somatic cells are all cells which aren’t reproductive cells

Question 11

State that no natural mechanism is known for making a deliberate change to a DNA sequence.​

Answer 11

No natural mechanism is known for making a deliberate change to a DNA sequence

Question 11

Discuss the impact of randomness of gene mutations.

Answer 11

If a mutation is caused in the wrong area that cell may grow uncontrollably and can cause cancer.

Question 12

Define genetic variation.

Answer 12

A requirement for evolution by natural selection

Question 12

State the source of new alleles of a gene.

Answer 12

Genetic mutation

Question 13

Compare the consequences of a germ cell versus somatic cell mutation.

Answer 13

If the gamete has a mutated gene, the allele will be present in the zygote after fertilization
If the somatic cell is mutated, then it will not be passed on to offspring

Question 14

State that gene mutation is the original source of all genetic variation.

Answer 14

Gene mutation is the source of genetic variation

Question 15

Distinguish between beneficial, neutral and harmful gene mutations.

Answer 15

Beneficial genetic mutation is natural selection
Negative genetic mutation is cancer
Neutral genetic mutation is the change in a codon that doesn’t change the AA sequence

Question 16

State the function of gene knockout studies.

Answer 16

Allows scientists to study the impact on an organism of removing a gene.

Question 16

Outline the method scientists use to “knockout” genes.

Answer 16

A technique where a targeted gene is inactivated or removed from an organism

Question 17

Describe the process of gene editing using CRISPR Cas9.

Answer 17

Guides the enzyme Cas9 to cut DNA at a specific location
A gRNA molecule is used to target a specific sequence in a gene as it has a sequence of complementary bases to the target sequences.
Enzyme Cas9 cuts the gene at the target location
Can knock out genes or insert a DNA sequence where a gene was cut.

Question 18

Outline uses of CRISPR Cas9 gene editing.

Answer 18

Gene therapy : replace or repair a gene responsible for genetic diseases
Genetic research : effective method to knock out genes, allowing researchers to better understand certain genes
Malaria prevention : modify genomes of mosquitoes, reduce spread of malaria

Question 19

Outline the ethical implications of gene editing.

Answer 19

Human Safety :
Risk of exploitation for eugenics : creating a superhuman

Question 20

List common examples of the products coded for by conserved sequences of DNA.

Answer 20

RNA polymerase, helicases, translation and transcription related sequences

Question 20

Define “conserved sequence” of DNA.

Answer 20

Identical or similar genes across a species or group of species

Question 21

State two hypotheses that account for conserved sequences between species.

Answer 21

Functional Constraint Hypothesis : gene sequences are essential to the structure and function of the protein coded by the gene. Any mutation is naturally selected against as the associated protein would not function
Slower Rates of Mutation Hypothesis : highly conserved sequences are under selective pressure to maintain their function, resulting in slower rate of mutation in these sequences.