Mutations and genetic variation

Question 1

What is depurination?

Answer 1

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

Question 2

What is deamination?

Answer 2

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

Question 3

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

Answer 3

When UV light dimerizes adjacent Thymine bases

Question 4

What are somatic mutations?

Answer 4

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

Question 5

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

Answer 5

Mosaicism

Question 6

What is a germline mutation?

Answer 6

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

Question 7

Variations in nucleotide sequences is what type of mutation?

Answer 7

Gene mutations

Question 8

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

Answer 8

Chromosomal

Question 9

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

Answer 9

A genomic mutation

Question 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?

Answer 10

Mutations impacting chromatin

Question 11

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

Answer 11

Chromosomal –multiple genes may be affected

Question 12

What are the four types of point mutations?

Answer 12

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

Question 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?

Answer 13

Silent

Question 14

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

Answer 14

Missense

Question 15

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

Answer 15

Nonsense

Question 16

What are three factors that contribute to small insertions/deletions

Answer 16

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

Question 17

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

Answer 17

Incorrect recombination

Question 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

Answer 18

Strand slippage

Question 19

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

Answer 19

Frameshift mutation

Question 20

What is the process by which homologous chromosomes line up?

Answer 20

Synapsis

Question 21

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

Answer 21

Synaptonemal complex

Question 22

What are chisasmata?

Answer 22

The sites of chromosomal crossover

Question 23

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

Answer 23

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

Question 24

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

Answer 24

Trismony

Question 25

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

Answer 25

Monosomy

Question 26

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

Answer 26

False

Question 27

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

Answer 27

13, 18, 21

Question 28

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

Answer 28

Patau syndrome

Question 29

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

Answer 29

Edward syndrome

Question 30

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

Answer 30

Down syndrome

Question 31

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

Answer 31

Mosaicisim

Question 32

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

Answer 32

By proofreading the bases it inserts as it transcribes DNA.

Question 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?

Answer 33

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

Question 34

What is Lynch syndrome (HNPCC)?

Answer 34

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

Question 35

What is the function of DNA glycosylases?

Answer 35

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

Question 36

When is nucleotide excision repair utilized?

Answer 36

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

Question 37

What is xeroderma pigmentosum?

Answer 37

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.

Question 38

What is non-homologus end joining?

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

Homologous end-joining.

Question 41

What is cytrabine? How does it work?

Answer 41

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

Question 42

What is cyclophosphamide? How does it work?

Answer 42

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

Question 43

What is doxorubicin? How does it work?

Answer 43

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

Question 44

Where do strand slippages usually occur?

Answer 44

Where there are repetitive areas of bases.

Question 45

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

Answer 45

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

Question 46

What is the order of nucleotide exicision repair?

Answer 46

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

Question 47

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

Answer 47

Xeroderma pigmentosum