Mutations

Question 1

When Sarah investigate the effects of the nuclear meltdown on animals in Chernobyl, she found the rate of mutation of organisms is significantly more than organisms in Kyiv.
What type of mutation is this and describe this mutation. Hence, state the effects of this mutation on these organisms.

(4M)

Answer 1

• Induced mutation
• Caused by exposure to mutagenic agents
• Mutagenic agents increases the rate of mutations, which causes (choose one):
  1. DNA replication error
  2. DNA breakage or lengthening
  3. Damage DNA structure/block DNA replication
  4. Causes damaged DNA cells to/DNA of the cell damage and multiply.

Question 2

Differenciate between somatic mutation and germline mutation.

Answer 2

Somatic mutation occurs in the body cells while germline mutation occurs in the gametes

Somatic mutation cannot be pass on to offspring while germline mutations can be pass on to offspring

Question 3

Differenciate between gene mutation and chromosomal mutation.

(4M)

Answer 3

• Gene mutation affects only one gene during DNA replication while chromosomal mutation effect more than one gene during DNA replication
• Gene mutation only affect one trait while chromosomal mutations affect multiple traits
• Gene mutation happens during DNA replication while chromosomal mutation happens during cell division

Question 4

List three types of mutations:

Answer 4

Subsitution
Deletion
Insertion

Question 5

Define frameshift mutations and describe how it can affect the gene.

Answer 5

• Insertion or deletion of one more bases
• Insertion or deletion results in the shift of reading frames

Question 6

A mutagen has caused a point mutation in one of the chromosomes. However, it has no effect on the organism as the protein maintains it’s normal structure.
What type of effect of mutation is this describing?

Answer 6

Neutral Mutation

Question 7

A mutagen caused a mutation resulting in a haemoglobin having a sickle shape. What effect of mutation is this?

Answer 7

Missense mutation

Question 8

A mutagen has cause a removal of the base of a DNA. This causes a protein to stop being produced. What type of mutation is this and how does it affect the gene?

Answer 8

Deletion has occured. This causes a frameshift, which change the reading template from the mutation onwards. This causes nonsense mutation.

Question 9

The duchenne form of muscle atrophy is a form of gene mutation that is unlikely to live past 20-25 years of age. The genes are contributed from two heterozygous individuals.
Describe what causes Duchennes and how can it affect a foetus .

Answer 9

The inheritant of homologous recessive genes from the mother, which forms lethal recessives.
Causes wasting of leg muscles, failure of respiratory muscles and death (to boys).

Question 10

Within the Ashkenazi population, there is a prevalence of Tay-Sachs disease within the community.

What is the cause the disease, the effects of the disease and explain how the recessive allele for Tay-Sachs Disease benefits the survival of the population.

(7M)

Answer 10

• There is variation in the gene pool
• such that there is a mutation of the HEXA gene
• causes the accumulation of lipids in the nervous system.
• The recessive allele is passed on by two heterozygous individuals
• causing a lethal recessive (causes death), which causes the frequency of that allele to decrease in the gene pool
• However, those who have heterozygous genes have a resistance to tuberculosis
• which favours the allele for Tay-Sachs.
• This increase the number of offspring with that particular allele in the gene pool.

Question 11

Describe five different types of chromosomal mutations.

(10M)

Answer 11

• Deletion. Part of the chromosome is lost or deleted.
• Non disjunction. The incomplete separation of chromosomes causes one daughter cell has an extra chromosome and one daughter cell to have less one chromosomes during meiosis
• Translocation. Parts of the chromosome break off and rejoined to the wrong chromosome.
• Duplication. The section of chromosome that appears twice
• Inversion. The section of chromosome breaks and the broken piece joins back but it’s the wrong way around. This changes the order of the chromosome.