4 Mapping Eukaryotic chromos by recombination

Question 1

when does recombination happen

Answer 1

meiosis 1 NOT MEISOSIS 2

Question 2

what is synteny

Answer 2

genes on the same chromo

Question 3

what is chaismata

Answer 3

site of crossing over

Question 4

what is recombination

Answer 4

a new combo of alleles

Question 5

what is recombination frequency

Answer 5

% chance of crossing over during meiosis

Question 6

which ones are linked and which are not linked AB/ab A/a;B/b

Answer 6

○ Notation: AB/ab = linked
○ A/a;B/b = unlinked

Question 7

double crossover at 1 site leads to ________

Answer 7

no information swapped

Question 8

linked genes lead to ____ crossing over, which means more ______ and less _____

Answer 8

less
parental
recombinant

Question 9

what is the RF formula

Answer 9

○ RF (recombination frequency) = # offspring w recombinant genotypes/ tot # offspring

Question 10

what is a test cross

Answer 10

○ Crossing ur hybrid w a homozygous recessive

Question 11

what is a test cross ratio

Answer 11

1;1;1;1

Question 12

TF - When asked “how many crossover can we detect” we count silent crossovers in our count

Answer 12

F, we do not count silent crossovers

Question 13

what is a silent crossover

Answer 13

Crossing over happened but letters are the same

Question 14

what does it mean if we have an RF of 0%

Answer 14

Genes are too close together on chromo to be split by crossing over

Question 15

what are syntenic genes

Answer 15

○ Genes can be so far apart on the same chromosome (linked) that they act like they are independently assorted

Question 16

TF all linked genes are syntenic

Answer 16

T

Question 17

TF all syntenic genes are linked

Answer 17

F, All Linked genes are syntenic but not all syntenic genes are linked

Question 18

if theres an RF less that 50% consider the genes _____ therefore, _______

Answer 18

linked
syntenic

Question 19

TF, If the genes are linked they are not mendelian which means they will not have the mendelian ratios

Answer 19

T

Question 20

what is our plan of attack is we are wanted to get the RF of a trihybrid cross

Answer 20

○ Identify parental, recombinant and double crossovers
○ Identify gene order
- Find the odd one out, that’s the middle gene
○ Calculate individual RFs
- DCs are always recombinant
- Parentals are never
- Count double crossovers in your RF calculations