Chapter 3 Mutations

Question 1

Mutations

What are they

Answer 1

• Change in order of nucleotides
• Can be either somatic mutations where it occurs in the somatic cell. EG) all cells expect gametes. These only affect individuals. An example is cancer.
• Can be germline where it occurs in the sex cells/gametes. This mutation is passed onto the next generation.

Question 2

Mutations

What can cause them

Answer 2

Errors in cell divide cause mutation

1. ​Translation
2. ​Transcription
3. ​DNA replication

Question 3

Types of mutations

What is a SNP

Answer 3

A single nucleotide is affected

Single nucleotide polymorphism

Question 4

Types of mutations

Silent/synonymous mutations

Answer 4

▪ A silent/synonymous mutation occurs when substitution results in a codon that codes for the same amino acid.
→ There is no change in the DNA.
→ No change in the translated Amino Acid.

Question 5

Types of mutations

Missense mutations

Answer 5

▪ A missense mutation occurs when substitution results in a change in one amino acid.

Question 6

Types of mutations

Nonsense

Answer 6

▪ A nonsense mutation occurs when substitution creates a stop codon (ie. early termination).
→ leads to early termination of translation of the transcribed gene sequence.

Question 7

Types of mutations

Insertions and deletions

Answer 7

▪ Insertions and deletions cause the addition or removal of a nucleotide.
Insertion is the addition of one or more nucleotides. Deletion is the loss of a nucleotide.
→ Usually results in a frame-shift mutation, which affects all codons ‘downstream’.
→ All codons from insertion or deletion will be nudged out by one.
→ This results in all the amino acids to be different from the original code.

Question 8

Mutations in chromosomes

Deletions

Answer 8

The removal of a section of DNA

Question 9

Mutations in chromosomes

Inversion

Answer 9

When a section of DNA is flipped/reversed

Question 10

Mutations in chromosomes

Translocation

Answer 10

When a section of a chromosomes swaps with a section of a non-homologous chromosome

Question 11

Mutations in chromosomes

Duplication

Answer 11

When a copy is made of a section

Question 12

Effects of mutations on survival

Neutral mutations

Answer 12

▪ Neutral mutations occurs when the nucleotide is unchanged by the change in an amino acid
→ The survival of an organism is not affected.
→ Occurs with silent mutations.
→ It can sometimes occur with missense mutations if the new amino acid has similar properties to the original.

Question 13

Effects of mutations on survival

Deleterious mutations

Answer 13

▪ Deleterious mutations disrupt the function of encoded proteins and impacts ability to survive.
→ This usually occurs with nonsense mutations with (usually) serious effects.
→ An organism can survive if they have a copy of the normal allele.

Question 14

Effects of mutations on survival

Transposable

Answer 14

▪ Transposable elements cause death if occurring in the exon.
→ These are less harmful in introns and can be passed on if in gametes.

Question 15

Effects of mutations on survival

Beneficial

Answer 15

▪ Beneficial mutations aid the survival of an organism.
→ Missense mutations can change the function of the original protein for the better.
EG: Having one allele of the sickle cell mutation prevents the catching of malaria.
→ Nonsense mutations may eliminate harmful proteins.
EG: Some people have nonsense mutations eliminate surface proteins needed by HIV to enter cells.

Question 16

Causes of mutations

Answer 16

▪ Mutations can be spontaneous due to errors in cell division.
▪ Mutations can also be induced by either chemical or physical mutagens.
▪ According to mutation research:
→ mutations arise spontaneously;
→ environmental influences effect mutations rate;
→ mutations are persistent;
→ mutations usually mean a disadvantage (premature death means alleles spread in population).
▪ Mutations can be invisible, subtle or severe - rarely beneficial.
▪ The effect depends on whether the mutations are in somatic or germ-line cells (gametes).

Question 17

Causes of mutations

Somatic cell mutations

Answer 17

▪ Somatic cell mutations occur only in affected body cells and any daughter cells produced by mitosis.
→ All other cells lack mutation.
→ Mutations usually build up, accelerate ell division and terminates apoptosis.
→ These mutations cannot be inherited.

Question 18

Causes of mutations

Germ-line mutations

Answer 18

▪ Germ-line mutations affect gametes so it can be inherited.
→ If so, present in every cell of the offspring.
→ This often leads to developmental abnormalities that cause spontaneous abortion.
→ If birth occurs, offspring may be born with severe disorders.
→ If consistently passed on, a new allele has entered the population.