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Flashcards in Mutations and genetic variation Deck (47):
1

What is depurination?

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

2

What is deamination?

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

3

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

When UV light dimerizes adjacent Thymine bases

4

What are somatic mutations?

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

5

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

Mosaicism

6

What is a germline mutation?

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

7

Variations in nucleotide sequences is what type of mutation?

Gene mutations

8

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

Chromosomal

9

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

A genomic mutation

10

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?

Mutations impacting chromatin

11

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

Chromosomal --multiple genes may be affected

12

What are the four types of point mutations?

1. Silent
2. missense
3. Nonsense
4. insertion/deletion

13

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?

Silent

14

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

Missense

15

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

Nonsense

16

What are three factors that contribute to small insertions/deletions

1. Incorrect recombination
2. Strand slippage
3. Intercalating agents

17

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

Incorrect recombination

18

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

Strand slippage

19

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

Frameshift mutation

20

What is the process by which homologous chromosomes line up?

Synapsis

21

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

Synaptonemal complex

22

What are chisasmata?

The sites of chromosomal crossover

23

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

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

24

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

Trismony

25

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

Monosomy

26

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

False

27

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

13, 18, 21

28

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

Patau syndrome

29

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

Edward syndrome

30

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

Down syndrome

31

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

Mosaicisim

32

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

By proofreading the bases it inserts as it transcribes DNA.

33

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?

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

34

What is Lynch syndrome (HNPCC)?

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

Increased colorectal cancer

35

What is the function of DNA glycosylases?

Recognize specific altered/damaged *bases* and repair them.

36

When is nucleotide excision repair utilized?

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

37

What is xeroderma pigmentosum?

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

What is non-homologus end joining?

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

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

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

40

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

Homologous end-joining.

41

What is cytrabine? How does it work?

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

What is cyclophosphamide? How does it work?

Treatment for hodgkins.

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

43

What is doxorubicin? How does it work?

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

44

Where do strand slippages usually occur?

Where there are repetitive areas of bases.

45

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

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

What is the order of nucleotide exicision repair?

1. Nucleases/helicases remove the bad segment
2. DNa Pol and ligase repair

47

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

Xeroderma pigmentosum