6.5 and 6.6

Question 1

Recombination prefers homologous because

Answer 1

no loss of nucleotides at repair site

Question 2

Homologous Recombination used in

Answer 2

Meiosis and DNA Damage Response

Question 3

Homologous Recombination specific for

Answer 3

Double Stranded Breaks (DSB).

Question 4

Homologous Recombination exchanges

Answer 4

similar/identical genetic information across two separate strands of DNA

Question 5

Meselson-Weigle Experiment

Answer 5

Bacteria (Lambda) was grown/maintained in
“Light” medium

Question 6

Lambda was chosen bc

Answer 6

Half DNA by weight so density of the whole virus reflects the density of its DNA

Question 7

Meselson-Weigle proved

Answer 7

crossing over also involves breakage and reunion of DNA molecule

Question 8

Yeast as a Model Organism

Answer 8

*Cheap
*Abundant
*Fast to grow
*Eukaryotic
*Easy to Genetically Manipulate
*Can be studied as Haploid or Diploid
–Yeast can undergo Meiosis

Question 9

Yeast

Answer 9

has help in the understanding of recombination

Question 10

Spo11

Answer 10

protein that makes a double strand break on on of the chromatids by cleaving the phosphodiester bond

Question 11

Exonuclease

Answer 11

enzyme that removes nucleotides from an end of a DNA molecule

Question 12

Dmc1

Answer 12

takes 3’ tail and promotes invasion into homologous chromatid – forms heteroduplex

Question 13

Heteroduplex

Answer 13

region of double stranded DNA in which two strands have nonidentical sequences
Formed during crossing-over
Held by hydrogen bonds

Question 14

D-loop

Answer 14

Structure where the two strands of a double stranded DNA molecule are separated for a stretch and held apart by a third strand of DNA

Question 15

D-loop stabilized by

Answer 15

binding of replication protein A (RPA)

Question 16

Spo11 is highly

Answer 16

conserved

Question 17

D-Loop connects with other 3’ tail to form

Answer 17

2nd heteroduplex

Question 18

Holliday junctions

Answer 18

interlocked regions of two sister chromatids in recombination intermediates

Question 19

Heteroduplex Regions

Answer 19

Expand outwards on both chromatids

Question 20

Resolvase

Answer 20

enzyme that breaks and joins DNA strands at Holliday junctions to separate nonsister chromatids during crossing-over

Question 21

Anticrossover helicase

Answer 21

helps disentangle the invading strand thus interrupting Holliday junction formation and preventing crossing-over

Question 22

If a cell were to respond to a DNA damage
event during homologous recombination,
where would there most likelybe an error?

Answer 22

Heteroduplex

Question 23

Branch migration

Answer 23

Holliday juncations move away from each other and enlarge the heteroduplx region between them

Question 24

exonuclease produces

Answer 24

two 3’ single-stranded tails

Question 25

Homologous Recombination steps

Answer 25

*Step 1: Spo11 causes DSB *Step 2: Exonuclease degrades 5’end of breaks. *Step 3: Strand invasion – 1st heteroduplex *Step 4: Holliday Junctions – 2nd heteroduplex *Step 5: Expansion of heteroduplex regions *Step 6: Resolving Holliday Junctions

Question 26

Spo11 prefers to cleave

Answer 26

particular genomic sites, resulting in hot spots for cross-over

Question 27

Gene Conversion

Answer 27

Where one allele is changed to another allele during recombination as a result of heteroduplex formation and mismatch repair during recombination

Question 28

Mitotic cells do not make

Answer 28

Spo11 (no homologous recombination

Question 29

Mitotic recombinantion occurs bc

Answer 29

damage by environment agents that result in double strand breaks or single strand nicks in DNA

Question 30

Tetrad analysis

Answer 30

alleles segregate equally into gametes

Question 31

Gene conversion produces

Answer 31

tetrads will not segregate equally (breaks Mendel's first low)

Question 32

Some organisms find it useful to have

Answer 32

site-specific recombination

Question 33

site-specific recombination is due to

Answer 33

recombinases

Question 34

site-specific recombination occurs only DNA target sites that are

Answer 34

less 200 base pairs long

Question 35

site-specific recombination is much

Answer 35

similar that homologous recombination

Question 36

Integration

Answer 36

insertion of one DNA molecule into another

Question 37

Cre-Recombinase

Answer 37

Recognizes LoxP sequences to perform recombination

Question 38

system becoming more frequently used in mouse-based research

Answer 38

FLP-FRT

Question 39

FLP-FRT system

Answer 39

using flippase (FLP) recombinase, derived from the yeast Saccharomyces cerevisiae FLP recognizes a pair of FLP recombinase target (FRT) sequences that flank a genomic region of interest

Question 40

Two types of site specific recombination

Answer 40

FLP-FRT

Question 41

Uses of site specific recombo

Answer 41

turn on or off expression of a specific gene

Question 42

Clustered Regularly Interspaced Short Palindromic Repeats

Answer 42

CRISPR

Question 43

CRISPR

Answer 43

Prokaryotic Anti-viral defense mechanism

Question 44

CRISPR/Cas9

Answer 44

induce double strand breaks at almost any position in the genome

Question 45

CRISPR/Cas9 allows for

Answer 45

edit genomes in vicinity of the breakage