Oct 16

Question 1

What 2 factors can damage DNA spontaneously?

Answer 1

Reactive oxygen species and water can nucleophillic attack

Question 2

What are the 3 types of DNA damage?

Answer 2

1. Spontanous and mutagen induced gene mutation
2. Recombination, unequal crossing over as the homologous chromosomes don’t line up, result is 1 longer and 1 shorter chromatid
3. Transposable elements: they are things that randomly insert intern genomes

Question 3

Describe the 2 types of point mutations

Answer 3

Missense is a base change that now means the codon encodes for a diff AA
Nonsense is when a stop codon is now there

Question 4

What are the 2 types of frameshift mutations, caused by slippage of what on what?

Answer 4

Slippage of new template strand, means it bunches up, and DNA poly doesn’t read a section of it in second generation, so deletion. Slippage of new strand formed means that next time that strand is replicated (second generation), the template strand has more codons inserted into it to match the new strand? so insertion

Question 5

What is the more common and less common form of each purine and pyrimidines?

Answer 5

Adenine and cytosine have amino, imino is rare
Guanine and thymine keto, enol is rare

Question 6

What do each of the following base pair with and what is the resulting new base pair?
1. Enol of thymine
2.Enol of guanine
3.Imino of Adenine
4. Imino of cytosine

Answer 6

1. Enol thymine base pairs with keto guanine, results in TA to CG
2. Enol guanine with keto thymine, GC to AT
3. Imino adenine with amino cytosine: AT to GC
   4.Imino cytosine with amino adenine, CG to TA

Enols and keto stay together, so the enol of one can pair with keto of other and then vice versa

Question 7

What are transition and transversion mutations and examples of each?

Answer 7

Transition is purine-pyrimidine to purine pyrimidine, so CG becomes TA or TA becomes CG.

Transversion is purine -pyrimidine to pyrimidine-purine. Like CG becoming GC or AT

Question 8

When do you get the mutated version of DNA following a substitution point mutation?

Answer 8

You get the tautomer in the first generation replication strands as the parental strands are replicated. When the first generation replicates, the strand with the mutation will have the strand based off it to have a different nucleotide in the second generation

Question 9

What would K53X mutation mean?

Answer 9

Lysine at codon 53 is replaced by a stop codon

Question 10

Indel mutations in multiples of what preserve the reading frame of the gene?

Answer 10

Multiples of 3

Question 11

What causes indel mutations, what is the result when in multiples of 3?

Answer 11

It is slippage of DNA polymerase, some codons are repeated more then originally, so trinucleotide repeat/expansion disorder

Question 12

Which codon expansion of repeats results in huntington’s. What about fragile x syndrome?

Answer 12

Huntingtons is CAG, fragile X is CGG

Question 13

In fragile X syndrome, 6-54 repeats of CGG are normal, 55-200 is a carrier, 200-1000 results in disease. How detect this?

Answer 13

With PCR then electrophoresis, as more PCR compies made, the number of CGG repeats will increase, so there will be some bands that are shorter, then some that are longer and longer as PCR makes more copies