Linkage And Recombination I Flashcards
Linkage keeps ________
particular genes together
What are linked genes?
Genes located close together on the same chromosome
Belong to the same linkage group
Do NOT assort independently
Crossing-over causes genes to _____
be mixed up
MD/MD x md/md ->MD/md
Example of?
Linkage: M and D are linked
Linkage keeps particular genes together
MD/MD x md/md -> MD/md, Md/Md
example of?
Crossing over
Define recombination
The sorting of alleles into new combinations
When does crossing over take place?
In meiosis
What is responsible for recombination?
Crossing over in meiosis
Gametes that contain only original combinations of alleles present in the parents are (recombinant/non-recombinant) gametes
nonrecombinant gametes
or also called parental gametes = MD and md
MD/md x md/md is an example of what type of cross?
Test cross
Progeny displays _______ of traits found in parents (P generation) and are nonrecombinant porgeny or parental progeny
original combinations
MD/md x md/md ->
if nonrecombinant
1/2 MD/md
and 1/2 md/md
MMDD x mmdd - >
If genes are not linked
MdDd
Mm/Dd x md/md ->
If not linked
1/4 MmDd, 1/4 mmdd, 1/4 Mmdd, 1/4 mm/Dd
MD and md are (recombinant/nonrecombinant) gametes
nonrecombinant
Md and mD are (nonrecombinant/recombinant ) gametes
recombinant
MmDd and mmdd are (nonrecombinant/recombinant) progeny
nonrecombinant
Mmdd and mmDd are (nonrecombinant/recombinant) progeny
recombinant
After a single crossover has taken place two chromatids that did not participate are unchanged. And the gametes that receive these chromatids are
(nonrecombinants/recombinants)
nonrecombinants
After a single crossover has taken place, two chromatids that did particpate contain new combinations of alleles. Gametes that receive these chromatids are (nonrecombinants/recombinants)
recombinants
For each meiosis in which a single crossover takes place, what type of gametes are produced? What are the end results of independent assortment vs linked genes?
Two nonrecominant gametes and two recombinant gametes will be produced. Same for both but there will be a 1.1.1.1 in independent assortment and linked will not be
If there is no crossing over only (nonrecombinant/recombinant) gametes will be produced
nonrecombinant
The frequency of recombinant gametes is always ____ the frequency of crossing over
50%
25+25
The maximum proportion of recombinant gametes is what? Why?
50% because 2 alleles out of 4 cross over so 1/2
The percentage of recombinant progeny produced in a cross is called what?
Recombination frequency
Recombination frequency =
of recombinant progeny/total number of progeny x 100%
What is coupling?
Wild-type alleles are found on one chromosome and mutant alleles are found on the other chromosome
What is coupling aka?
cis configuration
p+b+/pb
coupling
What is repulsion?
One chromosome carries a wild allele and a mutant allele and other carries the other wild and other mutant
What is repulsion aka?
trans configuration
p+b/pb+
Repulsion
Most numerous progeny types are those with either both wild-type or both mutant types is ______
coupling
Most numerous progeny types are those with one wild-type and one mutant allele and those with the other wild-type and the other mutant allele is _____
repulsion
