D1.3

Question 1

Define gene mutations

Answer 1

Structural changes or alterations in the DNA sequence of an organism.

Question 2

List the causes of gene mutations

Answer 2

Proofreading errors in DNA replication or transcription.
Physical- UV radiation
Chemical- Cigarette smoke, Nitrate preservatives
Infectious agent- HPV

Question 3

Distinguish between substitutions, insertions and deletions

Answer 3

Substitution- of one nucleotide with another
Insertion- of one or more nucleotides into a DNA sequence
Deletion- of one or more nucleotides from a sequence

Question 4

Define single nucleotide polymorphism

Answer 4

An SNP represents a variation at a single base-pair position in the DNA sequence of an individual. It occurs when a single nucleotide (A, T, C, or G) is substituted by another. These changes can manifest within both coding (gene-containing) and non-coding regions of the genome.

Question 5

Describe the consequences of base substitutions

Answer 5

Single-nucleotide polymorphisms (SNPs) are the result of base substitution mutations and that because of the degeneracy of the genetic code they may or may not change a single amino acid in a polypeptide.

Question 6

Describe the consequences of insertions and deletions

Answer 6

Include the likelihood of polypeptides ceasing to function, either through frameshift changes or through major insertions or deletions.

Question 7

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

Answer 7

Due to the genetic code’s degeneracy, multiple codons can encode for a single amino acid. Thus, a change in one codon might still produce the same amino acid. In such cases, even though a substitution has occurred, it doesn’t alter the amino acid or the protein’s function, hence termed as a ‘silent’ mutation.

Question 8

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

Answer 8

Mis-sense: change alters a single amino acid in a protein change (sickle cell anemia)
Nonsense: Change creates a premature STOP codon which leads to shorter polypetide (Cystic Fibrosis)

Question 9

Define frameshift mutation:

Answer 9

A frameshift mutation in a gene refers to the insertion or deletion of nucleotide bases in numbers that are not multiples of three

Question 10

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

Answer 10

The change in reading frame alters every amino acid after the point of the mutation and results in a nonfunctional protein.

Question 11

Define mutagen

Answer 11

A mutagen is an agent that induces a permanent change to the genetic material of an organism

Question 12

Discuss the impact of randomness of gene mutations

Answer 12

Mutations can occur anywhere although some bases have a higher probability of mutating than others. No natural mechanism is known for making a deliberate change to a particular base with the purpose of changing a trait.

Question 13

Distinguish between germ cells and somatic cells

Answer 13

Germ cells are the cells responsible for the sexual reproduction of new organisms. Regular body cells that repair and reproduce tissues are known as somatic cells.

Question 14

Compare the consequences of a germ cell versus somatic cell mutation

Answer 14

Germline mutations can be transmitted to offspring and every cell in the offspring will have the mutations meaning they are inheritable. Somatic mutations have little effect on the organism because they are confined to one cell and its daughter cells.

Question 15

Define genetic variation.

Answer 15

Variation results from small differences in DNA base sequences between individual organisms within a population.

Question 16

Discuss gene mutation as the original source of all genetic variation.

Answer 16

Although most mutations are either harmful or neutral for an individual organism, in a species they are in the long term essential for evolution by natural selection.

Question 17

State the source of new alleles of a gene

Answer 17

Mutation is a source of new alleles in a population.

Question 18

Distinguish between beneficial, neutral, and harmful gene mutations

Answer 18

The ‘good’ or advantageous that increase fitness, the ‘bad’ or deleterious that decrease it and the ‘indifferent’ or neutral that are not affected by selection because their effects are too small.

Question 19

State the function of gene knockout studies.

Answer 19

Investigating the function of a gene by changing it to make it inoperative.

Question 20

Outline the method scientists use to knockout genes

Answer 20

designing a guide RNA (gRNA) that targets a specific location in the genome,
delivering the gRNA and a Cas9 enzyme (which acts as a molecular scissors) to the target cell, and then allowing the cell to repair the cut in the DNA.

Question 21

Describe the process of gene editing using CRISPR Cas9

Answer 21

Uses a guide RNA to match a desired target gene, and Cas9 (CRISPR-associated protein 9)—an endonuclease which causes a double-stranded DNA break, allowing modifications to the genome

Question 22

Outline the ethical implications of gene editing

Answer 22

Some of the ethical dilemmas of genome editing in the germline arise from the fact that changes in the genome can be transferred to the next generations.

Question 23

Define conserved sequence of DNA

Answer 23

Identical or similar sequences across a species or a group of species.

Question 24

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

Answer 24

Examples of such sequences include those that lead to DNA replication, transcription and translation, and proteins involved in cellular respiration

Question 25

State two hypotheses that account for conserved sequences between species

Answer 25

One is that the functional requirements of the gene are those that the organism cannot survive without
The other is that some sequences of DNA are subject to slower mutation rates