Mutations

Question 1

What is a mutation?

Answer 1

A random change to genetic material

Question 2

Describe the effect of mutations

Answer 2

Effect depends on type and location

A protein requires the correct sequence of amino acids to function properly and if the base sequence of a gene is disrupted, the amino acid sequence may be disrupted aswell

Question 3

What are single gene mutations or point mutations?

Answer 3

Involves a change in one of the base pairs of a single gene

Question 4

What are the three types of point mutation?

Answer 4

Substitution

Insertion

Deletion

Question 5

Describe substitution as a point mutation

Answer 5

Substitution is when one base is swapped for another and a substitution mutation may result in a change in the amino acid sequence

Question 6

Describe the possible effects of substitution as a point mutation

Answer 6

Silent - has no effect on the protein sequence

Missense - results in an amino acid substitution

Nonsense - substitutes in a stop codon for an amino acid

Question 7

Describe insertion as a point mutation

Answer 7

Caused by the addition of one or more nucleotides into a section of DNA

FRAMESHIFT mutation

Question 8

Describe deletion as a point mutation

Answer 8

Caused by the removal of one or more nucleotides from the DNA

FRAMESHIFT mutation

Question 9

Describe the effects of frameshift mutations

Answer 9

When the codons are read at the ribosome the codon reading frame is shifted

This can result in completely different amino acids coded for or the stop sequence being misplaced

Can lead to a non-functioning protein

Question 10

What are chromosome mutations?

Answer 10

Chromosome mutations arise through changes in the structure of chromosomes

These changes occur when a chromosome breaks and the cell attempt to repair the break but in doing so, may not restore the chromosome to its original structure

Question 11

What are the 4 types of chromosome mutations?

Answer 11

Deletion

Duplication

Inversion

Translocation

Question 12

Describe deletion as a chromosome mutation

Answer 12

Where genes break off of a chromosome and the cell loses them

Question 13

Describe duplication as a chromosome mutation

Answer 13

Where genes from a matching chromosome are inserted in a break in a chromosome leading to duplicated genes

Advantage - Can produce a copy of a gene free from selection pressure (no competition)

Disadvantage - common form of cancer

Question 14

Describe inversion as a chromosome mutation

Answer 14

Where some genes break off of a chromosome and are rotated 180 degrees so that the genes become inverted

This can cause difficulties during the formation of gametes (non-viable gametes)

Question 15

Describe translocation as a chromosome mutation

Answer 15

Where part of a chromosome breaks and is joined on to a different chromosome

This can cause difficulties during the formation of gametes (non-viable gametes)

Question 16

What is the evolutionary importance of gene duplication?

Answer 16

Produces a second copy of the gene which is free from selection pressure so it can become altered without affecting the original genes function which may confer advantages to the organism

Question 17

What is polyploidy?

Answer 17

Polyploidy is duplication of all the chromosomes - resulting in extra sets

Result of an error during gamete formation

Polyploid plants are normally larger and have increased seed and fruit size which is of economic importance

Question 18

What happens if a polyploid plant has an uneven number of sets of chromosomes?

Answer 18

It is sterile allowing the production of seedless fruits

Question 19

Describe polyploidy in animals

Answer 19

It is thought that polyploidy contributed to the evolution of vertebrate animals

However, polyploid mammals fail to survive

Question 20

Effect fo mutations in non-coding DNA

Answer 20

Some regions of DNA are made up of nucleotide repeats which must be a certain length for the cell to function normally

Insertions and deletions change the length of the non-coding genes causing mutations

Question 21

What are splice site mutations?

Answer 21

One which substitutes, inserts or deletes one or more nucleotides at a site where introns are normally removed from the primary mRNA transcript by enzymes

This results in a different mature transcript being formed and therefore a different protein

Question 22

How changes in DNA sequence can lead to an inferior phenotype

Answer 22

Changes in the amino acid sequence can impact the function of the protein

Gene mutations often lead to an inferior version of the phenotype which can be lethal