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Enzymes > Mutations and genetic variation > Flashcards

Mutations and genetic variation Flashcards

1
Q

What is depurination?

A

The process by which purine bases are lost due to spontaneous hydrolyization

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2
Q

What is deamination?

A

Loss of an amine group by one of the bases–particularly cytosine (making uracil)

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3
Q

What is pyrimidine dimerization (in the scope of our lecture)?

A

When UV light dimerizes adjacent Thymine bases

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4
Q

What are somatic mutations?

A

Mutations in the genes of somatic cells–do not affect progeny

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5
Q

What is the result of somatic mutation early on in the development of the organism?

A

Mosaicism

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6
Q

What is a germline mutation?

A

A mutation in the sex cells–causes mutation in the offspring.

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7
Q

Variations in nucleotide sequences is what type of mutation?

A

Gene mutations

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8
Q

Rearragements, deletions, or duplications of chromosomal regions are what type of mutation?

A

Chromosomal

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9
Q

A surplus or loss of chromosomes is what type of mutation?

A

A genomic mutation

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10
Q

Changes in the methylation of DNA or in the modification of histone proteins that contribute to the control of gene expresses are what type of mutation?

A

Mutations impacting chromatin

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11
Q

What is likely to have a greater impact: mutations at the chromosomal level, or at the genome level?

A

Chromosomal –multiple genes may be affected

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12
Q

What are the four types of point mutations?

A
  1. Silent
  2. missense
  3. Nonsense
  4. insertion/deletion
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13
Q

A change in a single base that does not result in the change of the protein that the codon encodes is what type of point mutation?

A

Silent

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14
Q

A change in a single base that results in a single codon/amino acid to change is what type of point mutation?

A

Missense

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15
Q

A change in a single base that results in premature stopping of translation of the polypepetide is what type of point mutation?

A

Nonsense

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16
Q

What are three factors that contribute to small insertions/deletions

A
  1. Incorrect recombination
  2. Strand slippage
  3. Intercalating agents
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17
Q

Unequal crossover due to the presence of very similar base pairing between two separate chromosomes is what type of insertion/deletion?

A

Incorrect recombination

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18
Q

A DNA segment that has a repetitive sequence may inadvertently loop out during replication and cause a deletion during replication. What is the name for this type of insertion/deletion

A

Strand slippage

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19
Q

Insertion or deletion of a number of bases, n, where n=3x and x=1,2,3… results in what type of mutation?

A

Frameshift mutation

20
Q

What is the process by which homologous chromosomes line up?

A

Synapsis

21
Q

The protein complex that holds the homologous chromasomes together is called what?

A

Synaptonemal complex

22
Q

What are chisasmata?

A

The sites of chromosomal crossover

23
Q

Are genes that are close to each other on a chromosome more or less likely to crossover?

A

Less likely–the closer they are together, the more likely they are to be inherited together.

24
Q

What is the condition where there is an extra copy of a chromosome?

A

Trismony

25
Q

What is the condition where there is one less chromosome than usual?

A

Monosomy

26
Q

True or false: monosomy of an autosome can produce viable offspring

A

False

27
Q

Which autsomes can have an extra pair and still produce viable offspring?

A

13, 18, 21

28
Q

What is the condition called when there is an extra copy of chromosome 13?

A

Patau syndrome

29
Q

What is the condition called when there is an extra copy of chromosome 18?

A

Edward syndrome

30
Q

What is the condition called when there is an extra copy of chromosome 21?

A

Down syndrome

31
Q

What is the term for having the same genotyped cells within the same individual

A

Mosaicisim

32
Q

How does the exonuclease activity of DNA polymerase delta contribute to the accuracy of DNA replication?

A

By proofreading the bases it inserts as it transcribes DNA.

33
Q

If there is an issues in one of the DNA strands being replicated, how do enzymes tell which one is the new one and which is the original?

A

There are nicks in the new one. Helix distortions are also specifically recognized

34
Q

What is Lynch syndrome (HNPCC)?

A

A disease caharacterized by the propensity of DNA to mutate due to defects in the DNA repair mismatch system.

Increased colorectal cancer

35
Q

What is the function of DNA glycosylases?

A

Recognize specific altered/damaged bases and repair them.

36
Q

When is nucleotide excision repair utilized?

A

Where there are large changes in the structure of DNA (e.g. pyrimidine dimers)

37
Q

What is xeroderma pigmentosum?

A

A disease characterized by an extreme sensitivity to sunlight, skin pigment changes, and skin cancers due to a defect in the nucleotide excision repair mechanism.

38
Q

What is non-homologus end joining?

A

When breaks in DNA occur in two different strands, the chains are simply ligated back together, resulting in the loss of a nucleotide(s).

39
Q

Why does non-homologus end joining work without critical damage to the cell?

A

Most of the DNA does not encode protein; ligated areas are not expressed

40
Q

What is the process by which a homologus chromosome is used as a template to repair another chromosome?

A

Homologous end-joining.

41
Q

What is cytrabine? How does it work?

A

Inhibitor of DNA repair process.

Has an arabinose instead of ribose, causing it to be converted to cytrabine trisphosphate. Cytrabine trisphosphate then competes with DNAs, and thus blocks replication

42
Q

What is cyclophosphamide? How does it work?

A

Treatment for hodgkins.

It is converted to phosphoramide mustard, which is a bi-functional alkylating agent, forming intrastrand DNA cross links.

43
Q

What is doxorubicin? How does it work?

A

Anti-cancer agent that inhibits topoisomerase II, leading to doube strand breaks

44
Q

Where do strand slippages usually occur?

A

Where there are repetitive areas of bases.

45
Q

What is the order for repairing a spontaneous conversion of Cytosine to uracil (4 steps)?

A
  1. Uracil DNA glycosylase excises theuracil
  2. AP endonuclease breaks the local phosphodieaser bond
  3. DNA phophodiesterase removes the phosphate backbone of the a-purinc base
  4. DNA pol tries again
46
Q

What is the order of nucleotide exicision repair?

A
  1. Nucleases/helicases remove the bad segment

2. DNa Pol and ligase repair

47
Q

A defect in the nucleotide excision repair mechanism can lead to what disease?

A

Xeroderma pigmentosum

Enzymes (24 decks)

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