Topic 8 A Level Biology

Question 1

What is a mutation?

Answer 1

• A change in the DNA base sequence.

Question 2

Where do mutations occur?

Answer 2

• Mutations occur in normal body cells and gametes.

Question 3

What are the 6 type of mutations?

Answer 3

1) Substitution
2) Deletion
3) Addition
4) Inversion
5) Duplication
6) Translocation

Question 4

What happens during substitution?

Answer 4

• Where 1 base is substituted for another

Question 5

What happens during deletion?

Answer 5

• Where 1 base is lost

Question 6

What happens during addition?

Answer 6

• Where 1 or more base is added

Question 7

What happens during duplication?

Answer 7

• Where a sequence of bases or whole gene is inserted twice or multiple times.

Question 8

What happens during inversion?

Answer 8

• Where a base sequence is removed, rotated by 180 degrees and inserted back again.

Question 9

What happens during translocation?

Answer 9

• Where a base sequence is taken out and inserted at a different position in the genome.

Question 10

Why aren’t mutations completely harmful? (2 reasons)

Answer 10

1) Some mutations take place within introns.
2) Genetic code is degenerate so the sequence of amino acids coded for may still be the same as the new codon.

Question 11

Why do mutations cause harm?

Answer 11

• Mutations cause a frame shift meaning all bases shift in one direction so every codon is read differently.

Question 12

What are mutagenic agents?

Answer 12

• Substances that increase the rate of mutations.

Question 13

How do mutations work?

Answer 13

• Some chemicals may delete/alter bases.
• Radiation may alter the structure of DNA as problems occur during replication.

Question 14

What are the 2 properties of stem cells?

Answer 14

• Stem cells can divide and replicate.
• Stem cells can also differentiate.

Question 15

What are totipotent cells?

Answer 15

• A type of stem cell where division and differentiation can be applied to any type of body cell.
• They only occur for a very limited time in mammalian embryos.
• During development, only part of the DNA is translated, leading to specialisation.

Question 16

What are pluripotent cells?

Answer 16

• Descendants of totipotent cells that can specialise into any type of body cell except for cells that make up the placenta.

Question 17

What are multipotent cells?

Answer 17

• Cells that differentiate into a limited number of types of body cell.

Question 18

What are unipotent cells?

Answer 18

• Cells that differentiate into 1 type of cell.

Question 19

What is the use of pluripotent stem cells?

Answer 19

• Divide into unlimited numbers and can be used to treat human disorders.

Question 20

What is the use of unipotent cardiomyocytes?

Answer 20

• Could develop into new heart tissues.

Question 21

What is the use of induce pluripotent stem cells?

Answer 21

• A type of stem cell that is made by reprogramming adult body cells.

Question 22

What are the pros of IPS cells?

Answer 22

• There is no destruction of embryos, avoiding ethical issues.
• No risk of rejection