Chap 7- Linked Genes

Question 1

Certain ___ segregate as if they were ___ and are part of the same ____, this being inherited as a ___ unit (linked).

Answer 1

genes; linked; chromosome; single

Question 2

During ___ ____, synapsed chromosomes reciprocally exchange ____ which reshuffles (recombines) ___ between homologs.

Answer 2

Meiosis 1 Prophase 1; segments; alleles

Question 3

The frequency of ___ ___ is proportional to the distance between them

Answer 3

crossing over

Question 4

Genes assort ___ if they are on different chromosome but show ____ if they are on the same chromosome.

Answer 4

independently; linkage

Question 5

With ___ ___ of two pairs of chromosomes, each containing one ___ gene pair, no ___ is exhibited

Answer 5

Independent assortment; heterozygous; linkage

Question 6

Four genetically different ___, each containing a different combination of ____, are formed in ___ ____.

Answer 6

gametes; alleles; equal proportions

Question 7

In genes linked on the same chromosome where no ____ ___ occurs, only ___ genetically different ____ are produced

Answer 7

crossing over; two; gametes

Question 8

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

Answer 8

linkage; parental; noncrossover gametes

Question 9

Although complete ___ rarely occurs it is useful to consider that two ___ could be located so closely together that ___ are infrequent or undetectable

Answer 9

linkage; genes; crossover

Question 10

Crossover between two linked ___ involves two _____ and generates two new ___ combinations called ___ or _____.

Answer 10

genes; nonsister chromatids; allele; recombinant; crossover

Question 11

The two ___ not involved in the exchange are known as ____.

Answer 11

chromatids; noncrossover

Question 12

As the distance between two linked ___ increases, the proportion of ____ gametes increases.

Answer 12

genes; recombinant

Question 13

When the ___ of the two linked ___ are far apart, the number of ___ approaches and doesn’t exceed ___ percent.

Answer 13

loci; genes; recombinants; 50

Question 14

If 50% recombinants occur, the result is a ____ ratio of the four types (two ___ and two ___ gametes).

Answer 14

1:1:1:1; parental; recombinant

Question 15

Complete ___ is very rare. Recombination due to ___ is much more common.

Answer 15

linkage; crossing over

Question 16

The percentage of ___ resulting from ___ gametes depends on the ___ between the two genes on the ____.

Answer 16

offspring; recombinant; distance; chromosome

Question 17

The greater the distance between the two genes on the same chromosome, the ___ likely they are to be ___ to form a ___.

Answer 17

more; crossed over; recombinant

Question 18

Studies by Morgan with Drosophila show that ___ chromosomes in meiosis wrap around each other to create ___, X-shaped intersections, which are points of ____.

Answer 18

synapsed; chiasmata; genetic exchange

Question 19

Morgan suggested that such exchanges lead to ____.

Answer 19

recombinant genes

Question 20

Linked genes exist in a ___ order along the chromosome, and the variable amount of ___ occurs between any two genes during _____.

Answer 20

linear; exchange; gamete formation

Question 21

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

Answer 21

less; chiasma; crossing over

Question 22

The recombination frequencies between linked genes are ___ and the frequency of exchange is an estimate of the relative ___ between two genes along the chromosome.

Answer 22

additive; distance

Question 23

One ___ (mu) is defined as 1 percent recombination between ___ genes on a chromosome

Answer 23

Map unit; two

Question 24

___ found the chromosome map of ___ genes on the X chromosome to be ___

Answer 24

Sturtevant; three; additive

Question 25

The ___ frequency equals the sum of the ___ divided by the total offspring times 100

Answer 25

recombination; recombinants

Question 26

The farther apart two __ are along a ___, the more likely a random crossover will occur

Answer 26

loci; chromosome

Question 27

Only two of the four ___ of a ___ are involved in crossing over

Answer 27

chromatids; tetrad

Question 28

A single crossover (SCO) between two nonsister ___alters the linkage between the two ___ only if the crossover occurs between those two ___.

Answer 28

chromatids; genes; genes

Question 29

When two __ are close together, the ___ event may not include those genes

Answer 29

genes; crossover

Question 30

The percentage of __ involved in an exchange between two ___ is twice the percentage of ___ gametes produced.

Answer 30

tetrads; genes; recombinant

Question 31

Consider an exchange when 20% ___ gametes are formed, ___ occurred in 40% of the ___.

Answer 31

recombinant; crossing over; tetrad

Question 32

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.

Answer 32

crossover; tetrads; gametes

Question 33

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.

Answer 33

distance; multiple; chromatids; facilitate

Question 34

Double exchanges of genetic material results from ____ and can be used to determine the order of three genes on the ____

Answer 34

double crossovers; chromosome

Question 35

To study double exchanges, three pairs of genes must be investigated, each ___ for ___ alleles

Answer 35

heterozygous; two

Question 36

The mathematical probability of wo independent events occurring ___ is equal to the product of the individual ____

Answer 36

simultaneously; probabilities

Question 37

The expected frequency of ___ gametes is much lower than that of either ___ gametes class

Answer 37

double cross over; single crossover

Question 38

If four or five genes are being mapped, even fewer___ and ___ crossovers can be expected

Answer 38

triple; quadruple

Question 39

In ____, the parent producing the crossover gametes must be ___ for all three genes under consideration

Answer 39

three-point mapping; heterozygous

Question 40

The genotypes all of gametes can be determined accurately by ___ the phenotypes of the ___

Answer 40

observing; offspring

Question 41

A sufficient number of ___ must be produce

Answer 41

offspring

Question 42

The ___ F2 phenotypes occur in the greatest ___ of ___

Answer 42

noncrossover; proportion; offspring

Question 43

The ___ phenotypes occur in the ___ proportion

Answer 43

double-crossover; smallest

Question 44

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

Answer 44

complement; reciprocal classes

Question 45

The two ___ phenotypic classes are ALWAYS the ____ or ____ classes

Answer 45

largest; non-crossover; parental

Question 46

The two smallest= ____ classes

Answer 46

DCO

Question 47

The gene in the ___ classes that changes its linkage relationship is the ___ gene

Answer 47

DCO; middle

Question 48

The expected ___ of multiples exchanges between two genes can be predicted from the ___ between them

Answer 48

frequency; distance

Question 49

The ___ apart two genes are, the ___ the probability that undetected ____ will occur

Answer 49

farther; greater; crossover

Question 50

The degree of ___ increases as the distance between them ____

Answer 50

inaccuracy; increases

Question 51

The most ___ maps are constructed from closely ____ genes.

Answer 51

accurate; linked

Question 52

This double crossover is ___ because no ___ of alleles occurs

Answer 52

undetectable; rearrangement

Question 53

____ reduced the expected number of multiple ___ when a crossover event in one region of the ___ inhibits a second event nearby

Answer 53

Interference (I); crossovers; chromosome

Question 54

To ___ the disparities that result from interference, the _____ is calculated.

Answer 54

quantify; coefficient of coincidence

Question 55

The coefficient of coincidence (C) is the ___ of DCOs divided by the ___ of DCOs

Answer 55

observed; expected

Question 56

Interference can be quantified by the equation ___

Answer 56

I=1-C

Question 57

Interference is complete when no ___ occur

Answer 57

double-crossover

Question 58

Interference is ___ if fewer double crossover events than expected occur and ___ if more double crossover event than expected occur

Answer 58

positive; negative

Question 59

When two genes are close together, ___ interference occurs and the ____ of mapping is high

Answer 59

positive; accuracy

Question 60

As the distance between them ___, interference ___ and the accuracy of mapping ___

Answer 60

increases; decreases; decreases

Question 61

When genes are ___ together I will be close to ___, and when far apart, 1 will be nearly ___

Answer 61

close; 0.1; zero

Question 62

If more DCOs are recovered than expected, I will be a ___ number, suggesting that the calculated map distances are ___ due to ___ data

Answer 62

negative; inaccurate; insufficient