Chap 7- Linked Genes Flashcards
Certain ___ segregate as if they were ___ and are part of the same ____, this being inherited as a ___ unit (linked).
genes; linked; chromosome; single
During ___ ____, synapsed chromosomes reciprocally exchange ____ which reshuffles (recombines) ___ between homologs.
Meiosis 1 Prophase 1; segments; alleles
The frequency of ___ ___ is proportional to the distance between them
crossing over
Genes assort ___ if they are on different chromosome but show ____ if they are on the same chromosome.
independently; linkage
With ___ ___ of two pairs of chromosomes, each containing one ___ gene pair, no ___ is exhibited
Independent assortment; heterozygous; linkage
Four genetically different ___, each containing a different combination of ____, are formed in ___ ____.
gametes; alleles; equal proportions
In genes linked on the same chromosome where no ____ ___ occurs, only ___ genetically different ____ are produced
crossing over; two; gametes
In genes linked on the same chromosome where no crossing over occurs, only two genetically different gametes produced it demonstrated complete ____ and produces only ___ or _____ in equal proportions
linkage; parental; noncrossover gametes
Although complete ___ rarely occurs it is useful to consider that two ___ could be located so closely together that ___ are infrequent or undetectable
linkage; genes; crossover
Crossover between two linked ___ involves two _____ and generates two new ___ combinations called ___ or _____.
genes; nonsister chromatids; allele; recombinant; crossover
The two ___ not involved in the exchange are known as ____.
chromatids; noncrossover
As the distance between two linked ___ increases, the proportion of ____ gametes increases.
genes; recombinant
When the ___ of the two linked ___ are far apart, the number of ___ approaches and doesn’t exceed ___ percent.
loci; genes; recombinants; 50
If 50% recombinants occur, the result is a ____ ratio of the four types (two ___ and two ___ gametes).
1:1:1:1; parental; recombinant
Complete ___ is very rare. Recombination due to ___ is much more common.
linkage; crossing over
The percentage of ___ resulting from ___ gametes depends on the ___ between the two genes on the ____.
offspring; recombinant; distance; chromosome
The greater the distance between the two genes on the same chromosome, the ___ likely they are to be ___ to form a ___.
more; crossed over; recombinant
Studies by Morgan with Drosophila show that ___ chromosomes in meiosis wrap around each other to create ___, X-shaped intersections, which are points of ____.
synapsed; chiasmata; genetic exchange
Morgan suggested that such exchanges lead to ____.
recombinant genes
Linked genes exist in a ___ order along the chromosome, and the variable amount of ___ occurs between any two genes during _____.
linear; exchange; gamete formation
Two genes located relatively close to each other along a chromosome are ___ likely to have a ____ form between them, and it is less likely that ___ will occur
less; chiasma; crossing over
The recombination frequencies between linked genes are ___ and the frequency of exchange is an estimate of the relative ___ between two genes along the chromosome.
additive; distance
One ___ (mu) is defined as 1 percent recombination between ___ genes on a chromosome
Map unit; two
___ found the chromosome map of ___ genes on the X chromosome to be ___
Sturtevant; three; additive
The ___ frequency equals the sum of the ___ divided by the total offspring times 100
recombination; recombinants
The farther apart two __ are along a ___, the more likely a random crossover will occur
loci; chromosome
Only two of the four ___ of a ___ are involved in crossing over
chromatids; tetrad
A single crossover (SCO) between two nonsister ___alters the linkage between the two ___ only if the crossover occurs between those two ___.
chromatids; genes; genes
When two __ are close together, the ___ event may not include those genes
genes; crossover
The percentage of __ involved in an exchange between two ___ is twice the percentage of ___ gametes produced.
tetrads; genes; recombinant
Consider an exchange when 20% ___ gametes are formed, ___ occurred in 40% of the ___.
recombinant; crossing over; tetrad
When two linked genes are more than 50 map unites apart, a ___ theoretically can be expected to occur between them in 100 percent of the ___, yet only 50% of the ___ are affected.
crossover; tetrads; gametes
Single crossovers can be used to determine the ___ between two linked genes, but ___ crossovers between ___ of a tetrad ___ the production of more extensive chromosome maps.
distance; multiple; chromatids; facilitate
Double exchanges of genetic material results from ____ and can be used to determine the order of three genes on the ____
double crossovers; chromosome
To study double exchanges, three pairs of genes must be investigated, each ___ for ___ alleles
heterozygous; two
The mathematical probability of wo independent events occurring ___ is equal to the product of the individual ____
simultaneously; probabilities
The expected frequency of ___ gametes is much lower than that of either ___ gametes class
double cross over; single crossover
If four or five genes are being mapped, even fewer___ and ___ crossovers can be expected
triple; quadruple
In ____, the parent producing the crossover gametes must be ___ for all three genes under consideration
three-point mapping; heterozygous
The genotypes all of gametes can be determined accurately by ___ the phenotypes of the ___
observing; offspring
A sufficient number of ___ must be produce
offspring
The ___ F2 phenotypes occur in the greatest ___ of ___
noncrossover; proportion; offspring
The ___ phenotypes occur in the ___ proportion
double-crossover; smallest
Because the F2 phenotypes ___ each other (e.g. one is wild type and the other is mutant for all three genes), they are called ____ of phenotypes
complement; reciprocal classes
The two ___ phenotypic classes are ALWAYS the ____ or ____ classes
largest; non-crossover; parental
The two smallest= ____ classes
DCO
The gene in the ___ classes that changes its linkage relationship is the ___ gene
DCO; middle
The expected ___ of multiples exchanges between two genes can be predicted from the ___ between them
frequency; distance
The ___ apart two genes are, the ___ the probability that undetected ____ will occur
farther; greater; crossover
The degree of ___ increases as the distance between them ____
inaccuracy; increases
The most ___ maps are constructed from closely ____ genes.
accurate; linked
This double crossover is ___ because no ___ of alleles occurs
undetectable; rearrangement
____ reduced the expected number of multiple ___ when a crossover event in one region of the ___ inhibits a second event nearby
Interference (I); crossovers; chromosome
To ___ the disparities that result from interference, the _____ is calculated.
quantify; coefficient of coincidence
The coefficient of coincidence (C) is the ___ of DCOs divided by the ___ of DCOs
observed; expected
Interference can be quantified by the equation ___
I=1-C
Interference is complete when no ___ occur
double-crossover
Interference is ___ if fewer double crossover events than expected occur and ___ if more double crossover event than expected occur
positive; negative
When two genes are close together, ___ interference occurs and the ____ of mapping is high
positive; accuracy
As the distance between them ___, interference ___ and the accuracy of mapping ___
increases; decreases; decreases
When genes are ___ together I will be close to ___, and when far apart, 1 will be nearly ___
close; 0.1; zero
If more DCOs are recovered than expected, I will be a ___ number, suggesting that the calculated map distances are ___ due to ___ data
negative; inaccurate; insufficient
