Mutations

Question 1

Define a mutation

Answer 1

Change in a nucleotide sequence

Question 2

Define mutagenesis

Answer 2

The process of mutation generation.

Question 3

Give an example of a spontaneous mutation

Answer 3

Deamination of cytosine into uracil

2) deamination of 5-methylcytosine into thymine

Question 4

If deamination were to occur , approx after how many rounds of replication would the change be fixed ?

Answer 4

Two round

Question 5

What are a few examples of exogenous factors that can cause mutations ?

Answer 5

• ionising radiations
• free radicals
• mutagenic chemicals and anti cancer agents

Question 6

What are examples of endogenous factors that could cause mutations ?

Answer 6

• transposable elements

2) dna replication defects

Question 7

What is an example of a transposable element ?

Answer 7

Transposons

Question 8

What is a transposon and how do they work ?

Answer 8

A DNA sequence that can change its position within a genome.

-

Question 9

What is transposition

*hint : in relation to transposons

Answer 9

• the transposon can jump out of a gene and into another gene - activating or deactiving it.

Question 10

What is single nucleotide polymorphisms

Answer 10

• these are positions in the genome where some individuals have one nucleotide and others have a different nucleotide.

Question 11

What are the three types of micro mutations in a base sequence ?

Answer 11

• deletion
• insertion
• substitution

Question 12

What are 5 examples of macro mutations in chromosomes ?

Answer 12

• deletion
• duplication
• inversion
• substitution
• translocation.

Question 13

What is translocation - a type of macromutation

Answer 13

Rearrangements of parts of chromosomes between non-homologous chromosomes

Question 14

What is an inversion

Answer 14

Segment of a chromosome is reversed from end to end

Question 15

What is a transition substitution single nucleotide change ?

Answer 15

Where the change in base is to the same type. Of base

Eg purine to purine

Pyrimidine to pyrimidine

Question 16

What is a transversion substitution?

Answer 16

When there is anchange to a different type of base

For example purine to pyrimidine

Question 17

If there is a base substitution mutation in codon 7 of the haemoglobin gene in anaemia , why is there a change in the 6th AMINO ACID ?

Answer 17

Because the methionine start codon amino acid is removed - thus it would have been the 7th amino acid but now that the methionine is removed , it is the 6th amino acid that is changed from glutamic acid to valine.

Question 18

Define a missense mutation

Answer 18

• anpoint mutation where a single nucleotide change results in a codon that codes for a different amino acid.

Question 19

What is a non-sun opus mutation

Answer 19

• a single point mutation that results in a change in a single nucleotide which results a codon that codes for a different amino acid

Question 20

What what is a synonymous mutation

Answer 20

• silent / neutral mutations that do not have an effect on amino acid sequences

Question 21

How can a mutation have an effect on the polypeptide length?

Answer 21

1) a frame shift mutation

2) mutation of a stop codon ( also known as nonsense codon )

Question 22

How can you change the amount of gene product?

Answer 22

Alter promoter activity

• alter translational initiation at AUG
• prevents mRNA splicing
• reduce mRNA stability

Question 23

What are the two types of translocation ?

Answer 23

Reciprocal and

Question 24

What are the two types of inversions ?

Answer 24

Parade trip and pericentric

Question 25

What is robertsonian translocation?

Answer 25

— two different chromosomes break on the centromere

• the Q ( bottom) arms fuse. Whereas the P arms ( top) do not fuse
• this results In 45 chromosomes instead of 46.

Question 26

What is polyploidy?

Answer 26

• gain a haploid set of chromosomes , so you have 69 chromosomes instead of 46. You have 3 copies of the same chromosome number.

Question 27

What is the most common cause of polyspermy?

Answer 27

• two sperms fuse with one egg.

- three sets of DNA.

Question 28

What is aneuploidy?

Answer 28

Loss and gain of whole chromosomes

• for example in Down syndrome : 47,+21

Question 29

What is mosaicism

Answer 29

Two different genotypes from an individual which developed from a singly fertilsized normal egg.

• presence of two or more chromosomal different populations of cells(cell lines) in their body.
• caused by non-disjunction in mitosis

Question 30

What is a nonsense mutation

Answer 30

Ca change in nucleotide which results in a stop codon.

Question 31

What are symptoms of robertsonian translocation ?

Answer 31

• people don’t t even know that they have it.
• sometimes they have no symptoms
• could be at a higher risk of miscarriage, fertility ,
• you may have an increased risk of having a child with Down syndrome.
• people only find out about this disorder when they start to have children

Question 32

What is meiotic non disjunction

Answer 32

When the chromosomes are not separated properly during meiosis which could result in zygote having abnormal number of chromosomes

Question 33

Give three examples of chemical mutagens

Answer 33

1) reacting chemicals : react directly with the nitrogenous bases of DNA. For example nitrous acid reacts with nitrogenous bases of DNA and remove an amino group from purine/pyrimidine. = DEAMINATION
2) intercalating agent : the chemicals intercalate or slip in between two base pairs in DNA in the DNA helix. This alters the morphology of DNA at that position.
3) BASE ANALOGUE: these chemicals are morphologically similar to that of normal nitrogenous bases which means that during replications these molecules are incorporated instead of nitrogenous bases which results in mutations?