13. Intro To Mutations

Question 1

What are exogenous sources of mutation ?

Answer 1

ionising radiation
UV
Mutagenic chemicals

Question 2

What are endogenous causes of mutation?

Answer 2

DNA replication errors
Endogenous free radical damage from metabolism
Transposable elements

Question 3

What are transposable elements?

Answer 3

Specific DNA sequences >1 gene in length which move to random sites as a discrete unit.

Question 4

How can transposable elements cause problems?

Answer 4

Insertion can inactivate the target gene

Insertion may disrupt promotor region

Question 5

What are 3 types of single nucleotide mutations?

Answer 5

Deletion
Insertion
Substitution

Question 6

Which single nucleotide changes will lead to a frameshift?

Answer 6

Deletions and insertions will alter the reading frame of the DNA downstream of the mutation.

Question 7

What can be the effect of single nucleotide mutations?

Answer 7

Can change gene product
Can change the amount of gene product
Can change polypeptide length
Or may not have any effect at all

Question 8

What is a transition mutation?

Answer 8

Change to the same type of base. E.g purine to purine

Question 9

What is a translocation mutation?

Answer 9

Change to a different type of base. E.g purine to pyramidine

Question 10

What mutation is involved in sickle cell anaemia?

Answer 10

A nucleotide substation in the 6th amino acid, causing glutamate to change to valine.

Question 11

What is a mutation which alters the amino acid called?

Answer 11

missense

Question 12

What are mutations which do not have an effect called?

Answer 12

Silent or neutral

Question 13

What are mutations that change an amino acid to a stop codon called?

Answer 13

Nonsense - alter the length of the polypeptide

Question 14

What mutations would alter the amount of gene product?

Answer 14

Mutations affecting transcription and translation - altering promotor activity, altering translation initiation at AUG or preventing mRNA splicing (sequence specific)

Question 15

What types of chromosomal mutations can occur?

Answer 15

Deletions - lose gene(s)
Translocations - move to another chromosome
Inversions - after ds break
Insertions - transposable elements

Question 16

Why is a deletion chromosomal mutation more detrimental than an inversion or translocation?

Answer 16

There is loss of genetic information, inversion and translocation there is no loss of genetic information

Question 17

Define mutation.

Answer 17

A heritable alteration in a gene or chromosome

Or the process that produces the alteration.

Question 18

Mutations vary depending on the source causing them. Describe possible changes that can occur.

Answer 18

Base dimerisation (thymine)
Double or single strand breaks
Mismatches of base pairs
Deamination

Question 19

What can cause free radial production?

Answer 19

UV damage, smoking, ionising radiation, metabolism

Question 20

How can transposable elements affect genes?

Answer 20

insertion into a gene will break the genetic code and inactivate the gene.

Question 21

Transposing do not always have an effect. Why is this?

Answer 21

They may jump into a non-coding region of the gene.

Question 22

Transposing can increase transcription of genes, how?

Answer 22

By inserting into the promotor region, can activate transcription

Question 23

What are 2 sources of endogenous mutation?

Answer 23

Dna replication errors

Transposable elements

Question 24

When is chromosome inversion most likely to occur?

Answer 24

After misrepair of a double stranded break

Question 25

What is the difference between a chromosome substitution and a translocation?

Answer 25

A substitution is exchange of sections at any point in the chromosome, translocation is exchange of the ends of the chromosome.

Question 26

What are symptoms of sickle cell anaemia?

Answer 26

Impaired growth,susceptibility to infections, weakness and tiredness

Question 27

Which chain of haemoglobin is altered in sickle cell anaemia?

Answer 27

beta chain

Question 28

What type of mutation occurs in sickle cell anaemia?

Answer 28

Missense - altered amino acid

Single nucleotide substitution

Question 29

What type of mutations will change the length of the polypeptide?

Answer 29

Frameshift mutations
Mutations of stop codon
Nonsense mutations

Question 30

When might a deletion or insertion not result in a frameshift?

Answer 30

If 3 bases or a multiple of 3 in the correct reading frame, will just remove or add those amino acids