Ch 6 Genetic Linkage and Mapping - Exam 2! Flashcards
Define a linkage group
group of genes that located on the same chromosome
Linkage groups correspond to?
the number of haploid chromosomes
When genes A and B are on two different chromosomes, gametes are produced in?
equal proportions
When genes A and B are on the same chromosome and are very, very close together, this is known as __ __.
complete linkage
When genes A and B are on the same chromosome and are very, very close together, gametes are produced in ?
equal proportions
When genes A and B are on the same chromosome not so close, this is known as __ __
incomplete linkage
Incomplete linkage produces gametes in?
unequal proportions
When genes A and B are on the same chromosome and are very, very far apart, this is known as __ __ ___
complete incomplete linkage
Complete incomplete linkage produces gametes in?
equal proportions
What do new alleles often change?
activity of the cellular product of the gene; phenotype
When genes are in lowercase form they are usually?
recessive mutations
When genes are in uppercase form they are usually?
dominant mutations
What were Morgan’s two key proposals?
crossing over occurs
closer the gametes, the less likely a chiasma forms
Morgan proposed a __ array of genes on a chromosome
linear
Recombinant frequency is dependent on?
distance between genes
What is the equation for recombinant frequency (RF)?
of recombinant offspri5ng/ total # of offspring x 100%
What does recominbant frequency provide information on?
The physical location of genes on chromosomes
yy ww notates?
unknown linkage
yw/yw notates?
loci on the same chromosome
y/y w/w notates?
loci on different chromosomes
Alleles can be __ or __ on the chromosome
cis; trans
Define crossing over
physical exchange between non-sister chromatids of homologus chromosomes
Crossing over occurs duing __ __ of ___
prophase I; meiosis
When are two times crossing over is not detectable?
- if it occurs outside the two gene markers region
- If crossing over occurs and even number of times between the two marker genes
T/F: crossing over occurs more randomly along the length of chromosome pairs.
True
T/F: crossing over involves reciprocal exchange of unequal and corresponding segments
FALSE; equal
T/F Multiple crosses are not possible in crossing over
false
What is the purpose of genetic mapping?
to determine the gene loci on chromosomes
If genes are far, there are __ recombinant offspring
many
If genes are close, there are __ __ recombinant offspring
very few
Map distance =
of total recombinant offspring / total # of offspring x 100
1 map unit (mu) = _ centiMorgans (cM) = _% recombinant frequency
1;1
What is a test cross?
heterozygous crossed with a recessive homozygous to determine an unknown genotype
Recombinant offspring __ nonrecombinant offspring
<
Genetic mapping utilizes a __ cross
test
