6.3b Mutations & Mutagens (CQ - exam)

Question 1

How is it possible that some, but not all, mutations get passed from one generation to the next?

Answer 1

Mutations may be passed from one generation to the next because people can be carriers of the mutation even if not displaying symptoms of the mutation.

Question 2

Would a frameshift mutation occur if six nucleotides were deleted in a sequence of DNA? Explain your answer.

Answer 2

Yes, because the amino acids would be in a different sequence

Question 3

Which type of mutation would be least harmful to an organism: silent, missense, or nonsense? Explain your answer

Answer 3

A silent mutation would be least harmful to an organism because although present, does not alter function of gene and does not change the amino acid sequence of a protein.

Question 4

difference between gene mutations and chromosomal mutations?

Answer 4

• Gene mutations: the change in a single base pair within a DNA sequence
• Chromosomal mutations: the rearrangement of genetic material and often affect several genes.

Question 5

What are two cellular processes that can cause mutations?

Answer 5

1. Deletion
2. Insertion
3. Substitution

Question 6

the difference between a specific and a non-specific DNA repair mechanism.

Answer 6

An example of specific DNA repair is UV radiation causing 2 thymines to covalently bond causing a dimer. Photorepair is a specific repair that is a solution to the thymine dimer.

An example of non-specific DNA repair mechanisms is a repair mechanism that can mend many forms on damage. Excision repair is a non-specific repair mechanism that removes damaged DNA and replaces it with the correct sequence.

Question 7

two types of mutagens

Answer 7

1. Physical: changing DNA structure
   - Example of a physical mutagen is X-rays
2. Chemical: a molecule enters the nucleus of a cell and induce mutations by reacting with the DNA
   - Example of a chemical mutagen is carcinogens which can be from cigarette smoke

Question 8

10. Xeroderma pigmentosium (XP) is a rare genetic disease caused by defective photorepair mechanisms. Individuals with XP have a 1000-fold higher risk of skin cancer than those without XP.

Explain why individuals with XP have a higher risk of skin cancer

Answer 8

Individuals that have a defective photorepair mechanism would have a higher risk of skin cancer because photorepair is a specific repair that only mends thymine dimers. Thymine dimer is considered a potential factor for skin cancer, that can be caused by UV radiation. Without XP’s mechanisms that repairs the thymine dimer, people with this would have a higher risk of skin cancer.