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Linked genes violate which on Mendel's
Principles?
Mendel's 2nd Principle of Independent Assortment
TERM 2
linked genes
DEFINITION 2
genes located close together on the same chromosome
TERM 3
4 things about linked
genes
DEFINITION 3
1. they travel together during meiosis 2. arrive at the same
destination (same gamete) 3. they are NOT expected to
assort independently 4. CAN be seperated by crossing over --
-> recombination
TERM 4
If 2 homologous individuals were crossed and
DID assort independtly, what would their ratio
be?
DEFINITION 4
TERM 5
How can you tell if something did/did not
assort independently?
DEFINITION 5
IF THEY DID: ratio will be 9:3:3:1 IF THEY DID NOT: There will
be an excess of one or more of the F2 genotypes
Genes that are close together on the same
chromosome usually do what?
Segregate as a unit and are therefore inherited together.
TERM 7
recombination
DEFINITION 7
exchange of unique geneticmaterial between nonsister
chromatids during meiosis
TERM 8
linkage
DEFINITION 8
condition in which two or more loci (genes) tend to be
inherited together
TERM 9
crossing over
DEFINITION 9
exchange of genetic material between two homologous
chromosomes by breakage and union
TERM 10
What can seperate linked genes?
DEFINITION 10
1. crossing over ---> recombination
complete linkage
genes that are located very close together and doNOT exhibit
crossing over
TERM 17
Testing for linkage can be done with a
testcross, which requires?
DEFINITION 17
an individual that is heterozygous for both characterisitics
can be obtained by crossing a homozygous dominant with a
homozygous recessive
TERM 18
With complete linkage, what progeny are
produced?
DEFINITION 18
only nonrecombinant progeny
TERM 19
nonrecombinant gamets
DEFINITION 19
gametes that contain only the original combinations of alleles
present in the parents (parental gametes)
TERM 20
No new combinations of traits are formed in
complete linkage, why?
DEFINITION 20
because the genes affecting the two traits are completely
linked and are inherited together
recombinant gametes
gamets with new combinations of traits formed
TERM 22
When gametes assort independtely, what
types of gametes are produced?
DEFINITION 22
nonrecombinant and recombinant gametes in equal
proportions
TERM 23
Independent assort produces what ratio?
DEFINITION 23
TERM 24
Genes that exhibit crossing over are ________
linked.
DEFINITION 24
incompletely
TERM 25
linkage maps
DEFINITION 25
graphic illustrations detailing the location of loci along a
chromosome and the distance loci are apart
Single crossovers: the frequency of rec.
gametes is half the frequency of crossing
over bc?
each cros sover takes place between only 2 of the 4
chromatids of a homologous pair
TERM 32
What is the phenotypic ratio of a testcross for
2 independtely assorting genes?
DEFINITION 32
TERM 33
When linked genes undergo some crossing
over, the result is mostly _____ progeny.
DEFINITION 33
noncombinant progeny
TERM 34
recombinantion frequency
DEFINITION 34
percent of recombinant progeny produced in a cross
TERM 35
How is the recombinantion frequency
calculated?
DEFINITION 35
recombination frequency= (# of recombinant progeny/totaly
# of progeny) *100%
In crosses for linked genes, the __ of alleles on
the homologous chromosome is critical in
determining the outcome of the cross.
arrangement of alleles
TERM 37
Allelels in the heterozygours parent can be in
which two arrangments?
DEFINITION 37
coupled or repulsed
TERM 38
coupling
DEFINITION 38
arrangment in which wild type alleles are found on one
chromosome and mutant alleles are found on the other
chromosome
TERM 39
repulsion
DEFINITION 39
arrangment in which each chromosome contains one wild
type and one mutant allele
TERM 40
The ___ of linked genes on a chromosome
affects the results of a testcross.
DEFINITION 40
arrangment (coupled or repulsed)
Intra recom. of genes that lie far apart on the
SAME CHROMOSOME and inter recomb are...
genetically indistinguishable
TERM 47
What method is used to test for independent
assortment?
DEFINITION 47
chi-squared test of independence
TERM 48
What does the chi-squared test of
independence test for?
DEFINITION 48
- to evaluate whether the segregation of alleles at one locus
is independent od the segregation of alleles at another locus
TERM 49
table of segregation ratios
DEFINITION 49
contingency table
TERM 50
How is expected # calculated?
DEFINITION 50
expected # = (row total X column total)/grand total
How do you calculate chi
squared?
x^2= sum of (observed-expected)^2/expected
TERM 52
How do you calculate degrees of freedom?
DEFINITION 52
df=(number of rows-1) X (rows of columns-1)
TERM 53
If P > 0.05 then the genes....
DEFINITION 53
independently assort
TERM 54
If P < 0.05 then the genes...
DEFINITION 54
are linked
TERM 55
Physical distances between genes on a
chromosome are related to the....
DEFINITION 55
rates of recombination
double
crossover
when two seperate crossover events take place between two
loci
TERM 62
2 double stand crossovers produce...
DEFINITION 62
only nonrecombinant gametes
TERM 63
two-point mapping Depends
on?
DEFINITION 63
a testcross between two loci 1. Location 2. Distance
TERM 64
Discrepancies is genetic maps can be due
to...
DEFINITION 64
double crossovers between the two outer genes go
undetected, causing a discrepancy in the true map distance
TERM 65
three point mapping Depends
on?
DEFINITION 65
a testcross between 3 loci 1. Distance 2. Order of the Loci 3.
Distance greater than 50mu
In fruit flys, the heterozygous parent must be
female, why?
because no crossing over takes place in the male
TERM 67
Information needed for mapping comes
from...
DEFINITION 67
the gametes produced by the heterozygous parent
TERM 68
When determining if you have the correct
order of gene location, _ is compared with _.
DEFINITION 68
The double crossover is compared to the no crossover to
see if any genes are different.
TERM 69
The DC should have the same alleles as the
NC @ 2 loci and different alleles @ the locus
in the _____.
DEFINITION 69
MIDDLE
TERM 70
interference
DEFINITION 70
the degree to which one crossover interferes with additional
crossovers in the same region
If repulsed configuration, which progeny will
there be more of?
RECOMBINANTS
TERM 77
Greater than ___% means there is no linkage
and the genes assorted independtely.
DEFINITION 77
