chapter 9 - genetic diversity

Question 1

What is a gene mutation ?

Answer 1

• a change in the DNA base sequence

Question 2

How do mutations occur and what are thing that increase the rate of mutations ?

Answer 2

• they occur spontaneously if dna is misread during dna replication
• things that increase the rate of mutations are mutagens
• like ultraviolet/ionsing radiation, chemicals and viruses

Question 3

What are the three types of mutation ?

Answer 3

• substitution
• deletion
• insertion

Question 4

How do mutations affect the protein synthesis ?

Answer 4

• they can leas to a different amino acid sequence
• as the gene has changed
• this means we will get a different polypeptide
• and probably a different tertiary structure

Question 5

What are substitution mutations ?

Answer 5

• when one base is replaced by another
• which can cause the amino acid sequence to change
• but not all substitutions change the amino acid sequence
• because there is more than one triplet code that codes for the same amino acid
• this is the degenerate nature of dna

Question 6

What are deletion mutations ?

Answer 6

• when one base is removed from the sequence
• if a base is deleted, the base sequence shifts
• so all the triplets after the deletion change so the amino acid sequence also changes
• this is a frame shift

Question 7

What is an insertion mutation ?

Answer 7

• when one base is added to the sequence
• this also causes a frame shift
• and all the triplets codes after the insertion change so the amino acid sequence will also change

Question 8

What are missense, nonsense and frame shift mutations ?

Answer 8

• missence is when an amino acid is replace by another one because of a change to the triplet code
• nonsense is when there is a premature stop codon weaning not all the amino acids join the chain
• frame shift is when a base is added or removed so codons shift to either side so all the codons are read different so the amino acid is different

Question 9

What is chromosome mutation ?

Answer 9

• when there is a change to the structure or whole number of chromosomes
• these can happen spontaneously through cell division

Question 10

What are the two types of chromosome mutation ?

Answer 10

• polyploidy = when organisms have more than two sets of chromosomes, mostly seen in plants
• non-disjunction = when homologous chromosomes don’t separate during meiosis meaning there are gamers with extra or missing chromosomes , which leads to individuals with missing or extra chromosomes in all cells

Question 11

What is meiosis ?

Answer 11

• a type of cell division where a parent cell divides into 4 haploid cells where they are all genetically different from each other
• it involves 2 nuclear divisions

Question 12

What area the 2 stages of meiosis ?

Answer 12

• meiosis 1 - homologous chromosomes are separated = independent segregation
• meiosis 2 - chromatids are separated = crossive over
  -before this interphases happens so that each chromosome has 2 chromatids