session 9-mutagenesis

Question 1

Base substitutions can be transitional or transverse. What is the difference?

Answer 1

transitional=purine to purine OR pyrimidine to pyrimidine

transverse=purine to pyrimidine OR pyrimidine to purine

Question 2

Even if a point mutation is in non coding region, what else can be affected?

Answer 2

splice sites, promoter sequence and binding sites

Question 3

what does insertion/deletion of a single nucleotide (single base mutation) , a few nucleotides (triplets) or millions of nucleotides (tandem duplications) cause?

Answer 3

frameshift mutation

Question 4

what is a missense mutation?

Answer 4

a mutation in which one amino acid replaces another

Question 5

what is a nonsense mutation?

Answer 5

amino acid changes to stop codon

Question 6

what induces mutations?

Answer 6

chemicals and radiation

Question 7

chemicals that cause mutations are called…

Answer 7

mutagens

Question 8

what is a wild type trait?

Answer 8

trait that is most common within that population

Question 9

how does mismatch repair work?

Answer 9

enzyme detects incorrect pairing and excises and replaces it. Termed as ‘proofreading’

Question 10

how does excision repair work?

Answer 10

• damaged DNA is removed and replaced using dna polymerase
• Nucleotide excision-repairs up to 30 bases (repairs UV damage and carcinogens)
• base excision-replaces 5 bases max (repairs oxidative damage)

Question 11

what does the ‘guardian of the genome’ do and what is its actual name?

Answer 11

protein p53-if DNA damage is too severe and cannot be fixed..apoptosis is promoted

Question 12

what are oncogenes?

Answer 12

a gene which can transform a cell into a tumour cell

Question 13

what is a proto oncogene?

Answer 13

normal gene that can promote cell division or apoptosis. If mutates, it can become an oncogene and contribute to cancer

Question 14

when is southern blotting valuable?

Answer 14

when analysis of larger segments of DNA within and around gene is necessary
-also used to analyse triplet repeat disorder

Question 15

what is the general role of array comparative genomic hybridisation (Array CGH)?

Answer 15

compare patients DNA against normal control DNA to see if there are any chromosomal changes

Question 16

A point mutation can be 1 of 3 types of mutation. what are the 3 types?

Answer 16

• silent
• missense
• nonsense

Question 17

What is a silent mutation?

Answer 17

Single base substitution which does not substitute amino acid
Note:some can disrupt RNA splicing and cause heritable diseases, still.

Question 18

What do gains or losses of base pairs create, when they produce a frameshift?

Answer 18

Ptc-premature termination codons

Question 19

What happens to mRNAs that contain PTCs?

Answer 19

Degrades by nmd (nonsense mediated decay) and little or no protein is produced

Question 20

What is tautomeric shift?

Answer 20

Four bases-proton briefly changes position-behave as altered template base during DNA replication

Question 21

In tautomeric form, what base pairs with what?

Answer 21

C with A

T with G

Question 22

What is IQ

Answer 22

Aromatic amine food mutagen-found in cooked meats and cigarette smoke
Disrupts packing of DNA

Question 23

What do UV light photons do to DNA bases?

Answer 23

Causes advance thymine a to join with one another-resolve spontaneously though through photoreactivation

Question 24

When are the human genes that encode mismatch repair enzymes commonly mutated?

Answer 24

Cases of hereditary non polyps is colorectal cancer

Question 25

What happens in amniocentesis and when is it performed?

Answer 25

Aminiotic fluid is extracted from foetus and DNA sampled

15-20 weeks of gestation

Question 26

What is chorionic villus biopsy and when is it carried out?

Answer 26

Chorionic villi (tissue in placenta) extracted using catheter
Performed at 10-13 weeks of gestation