Lecture 9

Question 0

Linkage does what?

Answer 0

Keeps particular genes together

Question 1

Linked genes

Answer 1

• located close together on the same chromosome
• belong to same linkage group
• do not assort independently

Question 2

Crossing over does what?

Answer 2

mixes up genes

Question 3

Read about

Answer 3

crossing over and linkage in ch 7

Question 4

What is recombination?

Answer 4

the sorting of alleles into new combinations

Question 5

original combinations of alleles

Answer 5

nonrecombinant gamestes

Question 6

new cominations of alleles

Answer 6

recombinant gametes

Question 7

How do you know if something assorts independently?

Answer 7

Mix two homologous

Question 8

Independent assortment has different ratios than

Answer 8

something that has experienced crossing over

Question 9

crossing over occurs

Answer 9

in meiosis

Question 10

recombinatnt chromosomes can be found in?

Answer 10

anaphase I

Question 11

In meiosis II, genes that are normally linked?

Answer 11

will then assort independently and end up on different gametes

Question 12

Test Cross: If genes are linked

Answer 12

• gametes that contain only original combinations of alleles present in the parents are non recombinatnt gametes or parental gametes = MD and md
• progeny display original combinations of traits found in parents (p generation) and are non recombinatnt progeny or parental progeny

EX

Question 13

Test Cross: If genes are NOT linked

Answer 13

EX
MD and md are non recombinant gametes
Md and mD are recombinant gametes
MmDd and mmdd are non recombinant progeny
Mmdd and mmDd are recombinant progeny

Question 14

What do testcross reveal?

Answer 14

the effects of linkage

Question 16

If genes are completely linked

Answer 16

NO crossing over.

Question 17

independent assortment ratio

Answer 17

9:3:3:1

Question 18

After a single crossover has taken place:

Answer 18

• two chromatids that did not participate are unchanged
• gametes that receive these chromatids are nonrecombinants
• two chromatids that did participate contain new combinations of alleles
• gametes that receive these chromatids are recombitnants

Question 19

For each meiosis in which a single crossover take place:

Answer 19

-two nonrecominant gametes and two recombinant gametes will be produced (same as if there is independent assortment)

Question 20

If there is no crossing over:

Answer 20

Only nonrecombinant gametes will be produced

Question 21

What frequency of recombinant gametes is always?

Answer 21

half the frequency of crossing over… the max proportion of recombinant gametes is 50%

Question 22

What does a single crossover produce?

Answer 22

-half nonrecombinant gametes and half recombinant gametes

Question 23

Recombination frequency =

Answer 23

of recombinant progeny / total number of progeny X 100%

Question 24

coupling:

Answer 24

• wild-type alleles are found on one chromosome and mutant alleles are found on the other chromosome
• AKA: cis configuration
• p+b+/pb

Question 25

Repulsion

Answer 25

- one chromosome carries a wild allele and a mutant allele and the other carries the other wild and the other mutant - AKA: trans configuration - p+b/pb+

Question 26

most numerous progeny types are those w/ either both wild type or both mutant traits

Answer 26

coupling

Question 27

most numerous progeny types are those with one wild type and one mutant allele and those with the other wildtype and the other mutant allele

Answer 27

repulsion

Question 28

independent assortment on test cross

Answer 28

1:1:1:1

Question 29

complete linakge

Answer 29

1:1

Question 30

Linkage w some crossing over

Answer 30

50% or more nonrecombinant | less recombinant

Question 31

recombinant frequency

Answer 31

needs to be split btw the recobminat gametes

Question 32

Testing for independent assortment

Answer 32

(row total X Column total)/ grand total

Question 33

A two stranded double cross over btw two linked genes produces only?

Answer 33

nonrecombinant gametes

Question 34

chi square =

Answer 34

sum (observed - expected)^2/ expected

Question 35

df=

Answer 35

of rows-1

Question 36

if less than .05

Answer 36

there is a difference btw number of observed; epxected progency is probably not due to chance and they do NOT assort independently

Question 37

a two stranded double cross over

Answer 37

only non although middle has been recominbed