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BIO1334 - Genetics > Origins of Variation in Genomes > Flashcards

Origins of Variation in Genomes Flashcards

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Biology 101 flashcards
1
Q

Give an overall summary of mitosis:

A
  • Somatic cells
  • 2n –> 2n + 2n
  • (1n –> 1n + 1n, in haploid organisms)
  • Genetically identical daughter cells
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2
Q

Give an overall summary of meiosis:

A
  • Haploid gamete production
  • 2n –> n x 4
  • Genetically different daughter cells
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3
Q

What happens to homologous chromosomes during mitosis?

A

Remain separate throughout

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4
Q

What happens to homologous chromosomes during meiosis?

A

Pair and recombine

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5
Q

At which stage of meiosis I does homologous recombination occur?

A

Prophase

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6
Q

Is the DNA replicated at the prophase of meiosis I?

A

Yes

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7
Q

What is another way to describe homologous recombination?

A

Crossing over

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8
Q

What is visible crossing overs known as?

A

Chiasmata

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9
Q

What is homologous recombination?

A
  • Breakage and joining of DNA
  • Reciprocal
  • Genetic rearrangement
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10
Q

How does meiotic homologous recombination generate crossovers?

A
  • Enzyme Spo 11 and Mre 11 nuclease complex cuts one of the double stranded chromosomes
  • Repaired DNA double strand by either non homologous end joining or homologous recombination
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11
Q

How is DNA double strand breaks repair by non homologous end joining?

A
  • Loss of nucleotides due to degradation from ends
  • Blunt joining of ends
  • Deletion of DNA sequence has occurred
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12
Q

How is DNA double strand breaks repair by homologous recombination?

A
  • 2 different sisters chromatids
  • Loss of nucleotides due to degradation from ends
  • End processing and homologous recombination
  • Damage repaired by using information from sister chromatids
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13
Q

Which out of non homologous and homologous recombination are a universal process?

A

Homologous recombination

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14
Q

Describe in detail DNA double strand breaks repair by homologous recombination:

A
  • Double strand break
  • Exonuclease degrades 5’ ends and creates 3’ overhang
  • Strand invasion causes branch point known as heteroduplex structure (D-loop)
  • DNA synthesis and migration of branch point where the 3’ overhang is being repaired on double strand
  • Continued branch migration followed by pairing of newly synthesis DNA with top strand and top strand of DNA synthesis
  • DNA ligation where all the breaks in DNA are repaired by DNA ligase
  • Double stranded break is accurately repaired
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15
Q

How is a heteroduplex structure formed?

A
  • Synapsis catalysed by RAD51 and other proteins
  • Binds to 3’ single stranded end of damaged DNA
  • Forms a dynamic 3- stranded structure with ds-DNA
  • ‘Searches’ for homology
  • Structure is formed
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16
Q

Is homologous recombination repair of double strand breaks reciprocal or non-reciprocal?

A

Non-reciprical

17
Q

What is lost during homologous recombination can repair double strand breaks?

A

Local loss of heterozygosity

18
Q

DNA double stranded break repair by homologous recombination can occur in:

1) a haploid yeast cell in G1 phase of the cell cycle
2) human gametes
3) polyploid plant cells
4) somatic mammalian cells

A. 1) and 2)
B. 1) and 4)
C. 2) and 3)
D. 3) and 4)

A

D

19
Q

What are the two main ‘jobs’ of homologous recombination?

A

Repairing double strand breaks and generating crossovers

20
Q

How does meiotic homologous recombination generate crossovers?

A
  • Pair of homologous chromosomes
  • SPo11 and Mre11 nuclease complex break the double strand on one chromosome
  • Spo11 removes a part of that chromosome and exposes single stranded 3’ end
  • RecA-type strand exchange protein loaded (strand invasion
  • Forms d-loop going the two chromosomes
  • DNA Synthesis followed BY DNA ligation
  • Forming double holiday functions
  • The are two alternative paths which resolve holiday junctions by breakage and joining of DNA
  • First way: cutting DNA strands in the same plane producing a chromosome without crossover
  • Second way: cutting DNA strands in the different plane producing chromosomes with a crossover
21
Q

What is an holiday junction?

A

branched nucleic and structure containing four double stranded arms joined together

22
Q

What is linkage analysis?

A

Genes on a chromosome are linked both physically and genetically

23
Q

Is it proportional or disproportional relating to recombination frequency and distance apart for two linked genes?

A

Proportional

24
Q

Finish the sentence:

Genes further apart have…

A

a higher recombination frequency

25
Q

What can be exploited for gene targeting?

A

Homologous recombination

26
Q

What is gene targeting?

A

Targeting specific gene mutation in vivo via introducing DNA containing homologous sequences and selectable markers which are integrated in to DNA

27
Q

Describe gene targeting with a circular DNA:

A
  • Single crossover of SEL (circular DNA)

- Insertion of the gene into chromosome

28
Q

Describe gene targeting with linear DNA:

A

-Double crossover of SEL (linear DNA)
-The gene is deleted from the chromosome and replaced with the SEL
-

29
Q

Give examples of gene targeting with linear DNA:

A
  • Yeast gene deletion

- Knockout mice

30
Q

Describe homologous recombination in bacteria with circular DNA:

A
  • Chromosome and other DNA (e.g plasmid) present
  • Region og homology
  • Two parts of the DNA are fused together
31
Q

Describe homologous recombination in bacteria with linear DNA:

A
  • Homologous DNA and chromosome present

- Genetic recombination replaces a section of the chromosome with homologous DNA

32
Q

What can bacteriophage do within in bacterial cells?

A

Infect and reproduce

33
Q

Can recombination occur in bacteria via bacteriophage?

A

Yes

34
Q

Describe homologous recombination in bacteria with bacteriophage:

A
  • Bacteriophage inserts phage DNA
  • Recombination occurs in the cell (ignoring the chromosome)
  • Recombinant phage produce
35
Q

What is the bacteria to the bacteriophage during homologous recombination?

A

A host to reproduce

BIO1334 - Genetics (24 decks)

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