Deck 3: Independent Assortment of Genes

Question 1

In a trihybrid,how many different gamete genotypes can be produced with respect to the three genes of interest?

A)3
B)4
C)8
D)16
E)27

Answer 1

C

Question 2

Mendel's Y/y;R/r dihybrid pea plants were the F₁ of the cross between a double homozygous dominant and a double homozygous recessive.If we testcrossed these dihybrids,what proportion of the offspring would be recombinant and phenotypically resemble the F₁ dihybrid?

A)0%
B)25%
C)50%
D)75%
E)100%

Answer 2

A

Question 3

If an individual has 10 gene pairs,how many different gametes can be formed if 5 of the gene pairs are homozygous and the remaining 5 gene pairs are heterozygous?

A)20
B)32
C)60
D)64
E)1024

Answer 3

B

Question 4

A leucine-requiring mutant strain of haploid yeast is crossed to a cysteine-requiring mutant strain.Assuming independent assortment,what proportion of the spores produced will be mutant?

A)1/16
B)3/16
C)1/4
D)1/2
E)3/4

Question 5

If a plant of genotype A/a;B/b;C/c;D/d is selfed and the genes assort independently,how many different genotypes will be found among the progeny?

A)4
B)16
C)24
D)64
E)81

Question 6

Mendel crossed Y/Y;R/R (yellow wrinkled)peas with y/y;r/r (green smooth)peas and selfed the F₁ to obtain an F₂.In the F₂ what proportion of the yellow wrinkled individuals were pure-breeding?

A)1/9
B)3/16
C)1/4
D)3/4
E)9/16

Question 7

A pure line of Guinea pigs with genotype A/A;b/b is crossed to a pure line with genotype a/a;B/B.The F₁ male and female Guinea pigs are crossed to each other to generate the F₂.What proportion of the F₂ individuals are the result of a recombinant egg being fertilized by a recombinant sperm?

A)1/16
B)2/16
C)4/16
D)6/16
E)10/16

Question 8

Mendel crossed Y/Y;R/R (yellow wrinkled)peas with y/y;r/r (green smooth)peas and selfed the F₁ to obtain an F₂.What proportion of the F₂ individuals were pure-breeding?

A)1/9
B)3/16
C)1/4
D)3/4
E)9/16

Question 9

The pedigree below shows the inheritance patterns of two extremely rare,independent genetic conditions (represented with black and grey symbols,respectively).If individuals A and B have a child,what is the probability that it will have both conditions?

A)1/16
B)1/9
C)1/4
D)1/3
E)4/9

Question 10

If two mice of genotype F/f;G/g;H/h;I/i;J/j are repeatedly mated,how many different phenotypes will be found in the progeny? (Assume complete dominance for all genes.)

A)15
B)16
C)32
D)128
E)256

Question 11

A fish of genotype a/a;B/b is crossed to a fish whose genotype is A/a;B/b.What proportion of the progeny will be heterozygous for at least one of the genes? (Assume independent assortment.)

A)1/8
B)2/8
C)4/8
D)5/8
E)6/8

Question 12

The following is known about the inheritance of size and fur color in Holland lop rabbits:
•Crosses between large individuals only produce large individuals.
•Crosses between dwarf individuals produce both large and dwarf rabbits in a ratio of 1:2.Such crosses also produce some very small kits (baby rabbits)that generally die within a few days.
•Crosses between brown rabbits only produce brown kits.
•Some crosses between black rabbits produce only black kits,whereas others produce both black and brown kits.
•The size and fur-color phenotypes segregate independently.

-A large black doe (female rabbit)gives birth to nine black kits?five are large,and four are dwarf.What are the possible phenotypes of the kits' father?

A)black dwarf only
B)black dwarf,brown dwarf,black large,or brown large
C)black dwarf or black large only
D)black dwarf or brown dwarf only
E)black dwarf or brown large only

Question 13

Two pure-breeding mutant plants were crossed: One had small leaves (wild-type leaves are large),and the other made pink flowers (wild-type flowers are purple).All F₁ individuals had small leaves and purple flowers.Assuming independent assortment,what proportion of the F₂ individuals are expected to be phenotypically wild type?

A)1/16
B)3/16
C)1/4
D)9/16
E)3/4

Question 14

A female Drosophila with singed bristles is crossed to a male with sepia (dark brown)eyes.In the F₁,all females are wild type,and all males have singed bristles.F₁ males and females are crossed together,and the following F₂ phenotypic ratios are obtained.

748 wild-type females
753 wild-type males
742 singed females
747 singed males
249 sepia females
250 sepia males
244 singed, sepia females
246 singed, sepia males

If sn and se represent the mutant alleles of the singed and sepia gene,respectively,and sn⁺ and se⁺ are their wild-type counterparts,what are the most likely genotypes of the original parents?

A)X/X;sn/sn;se⁺/se⁺ and X/Y;sn/sn⁺;se/se
B)X/X;sn/sn;se⁺/se and X/Y;sn/sn⁺;se/se
C)X^sn/X^sn+;se⁺/se⁺ and X^sn+/Y;se/se
D)X^sn/X^sn;se⁺/se⁺ and X^sn+/Y;se/se
E)X^sn/X^sn;se⁺/se and X^sn+/Y;se/se

Question 15

Two pure lines obtained from Mendel's experiments are crossed to each other.The first line makes green smooth seeds (peas),and the second line has white flowers.All F₁ individuals have purple flowers and produce yellow wrinkled seeds.What proportion of the F₂ plants should have purple flowers and make green wrinkled seeds?

A)1/64
B)3/64
C)1/16
D)9/64
E)3/16

Question 16

The following is known about the inheritance of size and fur color in Holland lop rabbits:
•Crosses between large individuals only produce large individuals.
•Crosses between dwarf individuals produce both large and dwarf rabbits in a ratio of 1:2.Such crosses also produce some very small kits (baby rabbits)that generally die within a few days.
•Crosses between brown rabbits only produce brown kits.
•Some crosses between black rabbits produce only black kits,whereas others produce both black and brown kits.
•The size and fur-color phenotypes segregate independently.

-What are the expected phenotypes in the F₁ of a cross between a dwarf rabbit that breeds true for brown fur color and a large rabbit that breeds true for black fur color?

A)black dwarf only
B)black dwarf and black large only
C)brown dwarf and black dwarf only
D)brown dwarf,brown large,black dwarf,and black large
E)brown large only

Question 17

In a haploid fungus similar to Neurospora,a red-colored mutant is crossed to an alanine-requiring mutant.Assuming independent assortment,what proportion of the spores produced will be alanine-requiring?

A)1/16
B)3/16
C)1/4
D)1/2
E)3/4

Question 18

In hogs,a dominant allele B results in a white belt around the body.At a separate locus,the dominant allele S causes fusion of the two parts of the normally cloven hoof resulting in a condition known as syndactyly.A belted syndactylous sow was crossed to an unbelted cloven-hoofed boar,and in the litter there were:
$25 \%$ belted syndactylous
$25 \%$ belted cloven
$25 \%$ unbelted syndactylous
$25\%$ unbelted cloven
The genotypes of the parents can best be represented as which of the following?

A)B/B;S/S * b/b;s/s
B)B/b;S/s * b/b;S/S
C)B/b;S/s * B/B;s/s
D)b/b;S/s * B/b;s/s
E)B/b;S/s * b/b;s/s

Question 19

In the offspring of a dihybrid self,what percentage of the individuals are themselves dihybrid?

A)6)25%
B)12.50%
C)18.75%
D)25.00%
E)56.25%

Question 20

If genes assort independently,a testcrossed dihybrid characteristically produces progeny phenotypes in the ratio:

A)1:1
B)1:1:1:1
C)1:2:1
D)3:1
E)9:3:3:1

Question 21

Fruit color in a particular plant is controlled by a set of three QTLs (quantitative trait loci,or "polygenes")that work in an equal and additive manner.Each QTL has two alleles (i.e. ,A and a);each allele represented by a capital letter produces one dose of yellow pigment,while alleles represented with lower case letters do not produce any pigment at all.

-Assuming no effects by the environment,how many different shades of yellow fruit color are there?

A)3
B)7
C)9
D)12
E)64

Question 22

Fruit color in a particular plant is controlled by a set of three QTLs (quantitative trait loci,or "polygenes")that work in an equal and additive manner.Each QTL has two alleles (i.e. ,A and a);each allele represented by a capital letter produces one dose of yellow pigment,while alleles represented with lower case letters do not produce any pigment at all.

-A trihybrid plant (A/a;B/b;C/c)is selfed.Assuming no effects of the environment,what proportion of the offspring will have the same fruit color phenotype as the dihybrid parent?

A)0.031
B)0.125
C)0.250
D)0.312
E)0.422

Question 23

Meiosis I is about to start in a cell of a plant in which 2n = 18.At this stage,the cell has:

A)9 chromosomes,and a total of 18 chromatids.
B)18 chromosomes,and a total of 18 chromatids.
C)18 chromosomes,and a total of 36 chromatids.
D)36 chromosomes,and a total of 36 chromatids.
E)36 chromosomes,and a total of 72 chromatids.

Question 24

Which diagram most accurately shows the arrangement of homologous chromosomes during the first metaphase of mitosis?

A)
B)
C)
D)
E)

Question 25

A trihybrid cross is a cross between two individuals who are heterozygous for three genes.Assuming independent assortment and complete dominance,what phenotypic ratios would be observed in F₁?

A)27:9:9:9:3:3:3:1
B)16:9:9:3:3:1
C)12:9:3:1
D)9:3:3:1
E)1:1:1:1

Question 26

A corn plant of genotype A/a;B/B;C/c;D/d;E/e;f/f;G/g is selfed.What is the probability of producing a completely homozygous individual out of all possible offspring?

A)0.000
B)0.008
C)0.013
D)0.031
E)0.062

Question 27

Consider the following cross examining five unlinked genes.Identify what proportion of the progeny will be genotypically identical to parent 2?

Parent 1: A/a;B/b;C/c;D/d;E/e $\times$ Parent 2: A/A;b/b;C/c;D/d;E/e

A)1/216
B)27/128
C)1/64
D)1/16
E)1/32

Question 28

In the cross between a female A/a;B/b;c/c;D/d;e/e and male A/a;b/b;C/c;D/d;e/e,what proportion of the progeny will be phenotypically identical to the female parent? (Assume independent assortment of all genes and complete dominance.)

A)1/16
B)9/64
C)3/16
D)9/16
E)3/8

Question 29

In a Drosophila cross,you mate a parental line displaying crossed eyes (recessive trait,autosomal)and corkscrew bristles (recessive trait,autosomal)by a wild-type fly.The sites of the two genes are known to be unlinked.The F₁ flies are wild type.

You self the F₁ flies in the hope of regenerating the cross-eyed/corkscrew phenotype.

How many individual F₂ flies would you need to analyze to have 95% confidence of finding at least one cross-eyed/corkscrew fly?

A)16 flies
B)8 flies
C)32 flies
D)47 flies
E)216 flies

Question 30

You are studying meiosis in fungi with an organism in which the haploid chromosome number is 5 (n = 5).You combine two haploid cells together (strain 1 by strain 2),and then activate meiosis to regenerate haploid cells.What are the odds that any individual haploid cell will have either the five chromosomes from strain 1 or the five chromosomes from strain 2?

A)1/64
B)1/2
C)1/16
D)1/32
E)1/8

Question 31

Fruit color in a particular plant is controlled by a set of three QTLs (quantitative trait loci,or "polygenes")that work in an equal and additive manner.Each QTL has two alleles (i.e. ,A and a);each allele represented by a capital letter produces one dose of yellow pigment,while alleles represented with lower case letters do not produce any pigment at all.

-If a trihybrid plant (A/a;B/b;C/c)is testcrossed,what proportion of the offspring will have a fruit color phenotype that is different from both the trihybrid and the tester parents? (Assume no environmental effects.)

A)1/8
B)1/4
C)3/8
D)1/2
E)3/4

Question 32

What process occurring during meiosis ensures independent assortment?

A)the arrangement of homologous chromosomes on the metaphase plate
B)the fusion of male and female gametes
C)the pairing of homologous chromosomes in prophase
D)the replication of DNA and formation of sister chromatids
E)the "splitting apart" of sister chromatids in anaphase

Question 33

A male Drosophila melanogaster has the genotype A/a;B/b;C/c;X^D/Y.How many different sperm genotypes can it produce through meiosis of one single pre-gametic (2n)cell?

A)1
B)2
C)4
D)8
E)16

Question 34

A corn plant of genotype A/a;B/B;C/c;D/d;E/e;f/f;G/g is selfed.How many different completely homozygous genotypes could be produced?

A)2
B)4
C)8
D)16
E)32

Question 35

Which diagram most accurately shows the arrangement of homologous chromosomes during the first metaphase of meiosis?

A)
B)
C)
D)
E)

Question 36

In a plant in which 2n = 24,what is the total number of chromosomes present at the end of interphase?

A)6
B)12
C)24
D)48
E)96

Question 37

Which of the following is/are TRUE with respect to haploid and diploid cells?

A)Following DNA replication,haploid cells become diploid.
B)In diploid cells,meiosis I results in the formation of two haploid cells.
C)In haploid cells,condensed chromosomes have an "I" shape,while in diploid cells they have an "X" shape.
D)In haploid cells meiosis is simpler,owing to unpaired chromosomes.
E)The process of meiosis is identical in haploid and diploid cells.

Question 38

In a particular dihybrid,the two genes of interest,A and B,are located on different chromosomes.Which of the following diagrams does NOT represent a stage of meiosis in this organism? (Note: For each answer only some chromatids may be represented.)

A)
B)
C)
D)
E)

Question 39

Consider the following cross examining five unlinked genes.Identify what proportion of progeny will be phenotypically identical to parent 2?

Parent 1: A/a;B/b;C/c;D/d;E/e $\times$ Parent 2: A/A;b/b;C/c;D/d;E/e

A)1/216
B)27/128
C)1/64
D)1/16
E)1/32

Question 40

In a diploid organism 2n = 6,and there are two long,two intermediate,and two short chromosomes.What is the most accurate representation of a gamete resulting from meiosis in this organism?

A)
B)
C)
D)
E)

Question 41

A tomato plant with large leaves and round fruits was crossed to a plant with small leaves and oblong fruits.The F₁ consisted of plants with large leaves;about half of these plants made round fruits and the other half made oblong fruits.Two F₁ plants (one with round fruits and one with oblong fruits)were then analyzed through further crossing.The results were:


a)What are the genotypes of the two original parents?
b)What are the expected phenotypic ratios in the progeny of a cross between "F₁ plant #1" and a tester?
c)What gamete genotypes can "F₁ plant #2" produce?
Explain your reasoning behind each of your answers.

Question 42

Two albino strains of Neurospora crassa were isolated in two different laboratories.When either one was mated with wild type (orange)it produced 1/2 albino: 1/2 orange progeny.
a)What can you now deduce about the genetics of each of these albino strains?
b)Assume first that the two strains carry allelic mutations.Using appropriate symbols,diagram a cross of the two albino strains.Include the genotypes of the parents,a stick-and-circle diagram of the relevant chromosomes at metaphase I of meiosis,and the genotypes and ratios of the progeny.
c)Now assume that the two strains carry mutations in different genes,and that the genes are on different chromosomes.Answer the same questions as above.Assume that there are no crossovers between either gene and the centromeres.

Question 43

If stem length in a certain species of crops was solely determined by polygenic inheritance,how many different genes would be required in this system to explain the existence of 15 different stem lengths ranging from 15 to 29 cm?

Question 44

A woman with tritanopia (a rare form of inherited blue-yellow color blindness)marries a man who also has tritanopia.Their first daughter has normal color vision but is diagnosed with PKU.
a)Based on this information,what is the most likely mode of inheritance of tritanopia?
b)Using symbols of your own invention,write the genotypes of the two parents and of their daughter.(Assume independent assortment.)
c)What is the probability that the couple's next child is a son with tritanopia and PKU? (Assume independent assortment.)

Question 45

Vanessa has obtained two true-breeding strains of mice,each homozygous for an independently discovered recessive mutation that prevents the formation of hair on the body.The discoverer of one of the mutant strains calls his mutation naked,and the other researcher calls her strain hairless.To determine whether the two mutations are simply alleles for the same gene,Vanessa crosses naked and hairless mice with each other.All the offspring are phenotypically wild type.After intercrossing these F₁ mice,however,Vanessa observes 115 wild-type mice and 85 mutant mice in the F₂.
a)What is the most likely explanation for the segregation of wild-type mice and mutant mice in the F₂? Are the naked and hairless mutations alleles for the same gene?
b)Using symbols of your own choosing,indicate the genotypes of the parents,the F₁,and each of the phenotypic classes of the F₂ progeny.Describe any gene interactions in this set of crosses.

Question 46

Several pairs of light brown hamsters with identical genotypes were mated.Altogether,the F₁ was comprised of 143 individuals: 62 light brown,41 brown,38 beige (very,very light brown),1 dark brown,and 1 white.What mode of inheritance of the phenotype "fur color" could most easily explain these results?

Question 47

You generated a plant that is heterozygous for three quantitative trait loci (QTL).In the heterozygous state,each locus has one allele that contributes one dose of trait (pigment)and another allele that does not contribute a dose to the trait;genotype: R₁/r₁;R₂/r₂;R₃/r₃.If you testcross this plant (by r₁/r₁;r₂/r₂;r₃/r₃ all "0-dose" alleles)what distribution of pigment doses would be observed in the progeny?

A)1/8,three dose;3/8,two dose;3/8,one dose;1/8,zero dose
B)9/16,3 dose;3/16,2 dose;3/16,1 dose;1/16,0 dose
C)1/4,3 dose;1/4,2 dose;¼,1 dose;1/4,0 dose
D)1/2,2 doses;1/2,0 dose
E)One hundred percent will be pigmented,equally.

Question 48

In a perfectly controlled laboratory environment,a pure-breeding fish with a 23-mm tail was crossed to a pure-breeding fish with a 15-mm tail.In the F₁,all individuals had tails of an intermediate length: 19 mm.If tail length is a typical polygenic trait controlled entirely by the equal and additive effect of two unlinked genes,each with two alleles ("+" and "-"),what phenotypic ratios do you expect to find in the F₂?

Question 49

Define Mendel's experimental evidence for diploid chromosome content in pea plants.

Question 50

You just isolated a new strain of mutant mice,and preliminary matings suggest that the new mutant phenotype is not inherited autosomally.Circumstantial evidence seems to indicate that the mutant phenotype may be following either an X-linked dominant or a mitochondrial-type inheritance pattern.
a)What informative crosses would you set up to distinguish between these two possibilities?
b)How would you interpret your results?

Question 51

In a species of Mexican mollies,fish with ragged fins and nonragged fins were found.When mollies of a true-breeding (i.e.,pure-breeding)ragged strain were crossed with nonragged fish,the F₁ all had ragged fins,and in the F₂,three ragged appeared to one nonragged.Diagram this cross,letting R = ragged and r = nonragged,and give parental phenotypes,genotypes,and germ cells,as well as F₂ genotypes and phenotypes.

Question 52

Suppose red-striped laughing frogs are diploid and have 32 chromosomes in somatic cells.Answer the following questions as they pertain to these vanishingly rare but beautiful creatures.
a)How many pairs of homologous chromosomes does a red-striped laughing frog have in its somatic cells?
b)How many chromosomes are there in a haploid set?
c)How many chromosomes are there in a mature sperm cell?
d)How many chromosomes are there in a somatic cell just after mitosis?
e)How many double-stranded DNA molecules are there in a somatic cell as mitosis is about to start?
f)How many chromosomes are there in a cell prior to DNA replication?

Question 53

An arginine-requiring strain of Neurospora is crossed to a wild-type (prototrophic)strain.
a)In the first cross,half of the progeny are arginine-requiring and half are wild type.What does this tell you about the genetic basis of the arginine-requiring mutant?
b)In the second,the progeny are 83 arginine-requiring and 13 wild type.The germination percentage of ascospores is 95/100%.Explain these results simply,and tell briefly how you would confirm your explanation.

Question 54

The pedigree below shows the inheritance of a rare muscle condition in bats.What inheritance model best explains the peculiar pattern?

Question 55

Two haploid yeast cells,one wild type and one having a mutation blocking the synthesis of adenine,were mated to produce a diploid zygote.Through asexual reproduction (mitosis),this zygote gave rise to hundreds of identical cells,and all were wild type in phenotype.These (diploid)cells were then induced to undergo meiosis,and the progeny (a random sample of haploid meiotic products)consisted of 214 cells able to grow without adenine and 203 unable to grow without adenine.
a)Diagram the cross,picturing the chromosomes of the parents,the zygote,metaphase I,and the meiotic products.
b)How many genes are involved?
c)What are the dominance relationships of the alleles of the gene or genes?