Suppose that a single gene controls fruit color in mango.Yellow fruit (Y)is dominant to red fruit (y).Suppose a true-breeding yellow mango plant was crossed with a red-fruited plant,and the resulting F1 was selfed.The F2 segregated as expected.If one of the yellow-fruited plants was randomly selected and selfed,what is the probability that its progeny would segregate for fruit color? Explain your logic.

The F 2 consists of ¼ YY: ½ Yy : ¼ yy.Thus

Exam 2: Single-Gene Inheritance

Loppins are fictitious (but useful)diploid invertebrates that produce large offspring and normally have long antennae.Short antennae mutants also exist.Unfortunately for the geneticists working on these organisms,the males' antennae don't fully develop until the loppin equivalence of "middle age." A female with short antennae is crossed to a young male,and all the females in their offspring have the short antennae mutant phenotype.A subset of these F₁ females are crossed to a middle-aged male with short antennae,and all the females produced by these crosses have short antennae.However,all the crosses between the F₁ females and their brothers produce both short antennae and long antennae loppins in a ratio of about 3:1.How can these results be explained? Provide the genotypes of as many individuals as possible.

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Question 1

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The 3:1 ratio obtained in the cross between brothers and sisters suggests that short antennae (S)is dominant to long antennae (s),and that the F₁ females and their brothers are heterozygous (S/s).The young male used in the original cross is probably homozygous for the long antennae allele (s/s);the middle aged male with short antennae is probably homozygous (S/S,because all the progenies have short antennae).The cross between F₁ females and the middle aged male produces about 50% S/s and 50% S/S individuals;the cross between the F₁ females and their brothers produces about 25% S/S,25% s/s and 50% S/s,hence the observed phenotypic ratios.

Consider the following pedigree of a rare autosomal recessive disease.Assume all people marrying into the pedigree do not carry the abnormal allele. a)If individuals A and B have a child,what is the probability that the child will have the disease? b)If individuals C and D have a child,what is the probability that the child will have the disease? c)If the first child of C * D is normal,what is the probability that their second child will have the disease? d)If the first child of C * D has the disease,what is the probability that their second child will have the disease?

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a)Choosing M for unaffected and m for the disorder,male B must be M/m,and female A has a 2/3 chance of being M/m.The overall chance of an affected child is 1 * 2/3 * 1/4 = 1/6.

b)If C's mother A is heterozygous,C stands a 1/2 chance of being heterozygous.D's mother must be heterozygous,and D stands a 1/2 chance of inheriting that heterozygosity.The overall chance of an affected child is 2/3 * 1/2 * 1 * 1/2 * 1/4 = 1/24.

c)The probability is still 1/24.

d)Now that we know individuals C and D must both be M/m,the chance of the second child being m/m is 1/4.

In pet rabbits,brown coat color is recessive to black coat color.A black female rabbit gives birth to four black-coated and three brown-coated baby rabbits.What can be deduced about the genotype of the baby rabbits' father?

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You have three jars of gumballs.The first jar has 100 white gumballs and 25 green,the second jar has 50 white and 150 blue,and the third jar contains 500 white and 10 red. If you randomly draw one gumball from each jar,what is the probability for $\textbf{ all white gumballs? }$

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Question 4

Suppose that a single gene controls fruit color in mango.Yellow fruit (Y)is dominant to red fruit (y).Suppose a true-breeding yellow mango plant was crossed with a red-fruited plant,and the resulting F₁ was selfed.The F₂ segregated as expected.If one of the yellow-fruited plants was randomly selected and selfed,what is the probability that its progeny would segregate for fruit color? Explain your logic.

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Question 5

What is the mechanism that ensures Mendel's first law of segregation?

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Question 6

What is the most likely mode of inheritance of the exceptionally rare condition represented in the pedigree below,and why?

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Question 7

A phenotypically normal woman is heterozygous for the recessive Mendelian allele causing phenylketonuria,a disease caused by the inability to process phenylalanine in food.She is also heterozygous for a recessive X-linked allele causing red-green colorblindness.What percentage of her eggs will carry the dominant allele that allows normal processing of phenylalanine and the X-linked recessive allele that causes colorblindness?

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Question 8

Suppose that red flower color (RR or Rr)is dominant to white flower color (rr)in a petunia.A friend has a petunia plant with red flowers and wants to determine whether the plant is RR or Rr. a)What cross could you perform to help your friend determine the genotype of his petunia plant? b)How will this cross help you determine the genotype of your friend's red-flowered petunia? That is,how will the results from this cross differ if the red-flowered petunia is RR versus Rr?

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Question 9

What is the maximum number of heterozygous genotypes that could be produced by monohybrid self?

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Question 10

A man whose mother had cystic fibrosis (autosomal recessive)marries a phenotypically normal woman from outside the family,and the couple considers having a child. a)If the frequency of cystic fibrosis heterozygotes (carriers)in the general population is 1 in 25,what is the chance that the first child will have cystic fibrosis? b)If the first child does have cystic fibrosis,what is the probability that the second child will be normal?

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Question 11

The following pedigree concerns the autosomal recessive disease phenylketonuria (PKU).The couple marked A and B are contemplating having a baby but are concerned about the baby having PKU.What is the probability of the first child having PKU? Unless you have evidence to the contrary,assume that a person marrying into the pedigree (i.e.,not a descendant of the two parents at the top of the pedigree)is not a carrier.The filled-in individuals have PKU.

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Question 12

A plant is heterozygous at three loci.How many different gamete genotypes can it theoretically produce with respect to these three loci?

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Question 13

The black and yellow pigments in the coats of cats are controlled by an X-linked pair of alleles.Females heterozygous for these alleles have areas of black and areas of yellow in their coat (called tortoise-shell,or calico if there are also patches of white hair). a)A calico cat has a litter of eight kittens: one yellow male,two black males,two yellow females,and three calico females.Assuming there is a single father for the litter,what is his probable color? b)A yellow cat has a litter of four kittens: one yellow and three calico.Assuming there is a single father for the litter,what is the probable sex of the yellow kitten? c)How would you prove that XO cats are phenotypically female? What female kitten colors (with respect to yellow,calico,and black)would you look for in which types of parental color crosses?

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Question 14

A dominant gene b⁺ is responsible for the wild-type body color of Drosophila;its recessive allele b produces black body color.A testcross of a heterozygous b⁺/b female by a black b/b male gave 52 black and 58 wild-type progeny.If a black female from these progeny were crossed with a wild-type brother,what phenotypic ratios would be expected in their offspring?

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Question 15

In the late 1800s,Mendel defined two fundamental laws of transmission genetics;these were subsequently used to establish chromosome theory as scientists examined visible chromosomes in meiotic cells.Define these two laws,and diagram where in the process of meiosis these two processes actually occur.

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Question 16

a)In families with four children,what proportion of the families will have at least one boy? b)In families with two girls and one boy,what fraction of the families will have the boy as the second child? c)In families with four children,what fraction of the families will have the gender order male-female-female-male?

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Question 17

The wild-type eye color in the fruit fly Drosophila melanogaster is dark red,as a result of a mixture of bright red and brown pigments."Enzyme A" is encoded by the "a" gene,and is required to synthesize the bright red pigment.A lack of red pigment results in a somewhat brown eye color.You cross two fruit flies who are heterozygous for a recessive mutation that completely inactivates the "a" gene.What proportion of their offspring will have a recessive eye color phenotype?

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Question 18

The following pedigree shows the inheritance of a mild,but very rare condition in Siberian Husky dogs.If individuals 1 and 2 are crossed,what is the probability that they will produce an affected pup?

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Question 19

Below is the pedigree of a family where some individuals are affected with a mild condition of the skin. a)Based on the pedigree,what is the most likely mode of inheritance of this condition,and why? b)Indicate the respective genotypes of each individual represented.For individuals who could have two or more genotypes,calculate the relative probability of each possible genotype. c)What is the probability that individuals 1 and 2 will have an affected daughter?

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Question 20

Showing 1 - 20 of 51

In pet rabbits,brown coat color is recessive to black coat color.A black female rabbit gives birth to four black-coated and three brown-coated baby rabbits.What can be deduced about the genotype of the baby rabbits' father?

You have three jars of gumballs.The first jar has 100 white gumballs and 25 green,the second jar has 50 white and 150 blue,and the third jar contains 500 white and 10 red. If you randomly draw one gumball from each jar,what is the probability for $\textbf{ all white gumballs? }$

What is the mechanism that ensures Mendel's first law of segregation?

What is the most likely mode of inheritance of the exceptionally rare condition represented in the pedigree below,and why?

What is the maximum number of heterozygous genotypes that could be produced by monohybrid self?

A plant is heterozygous at three loci.How many different gamete genotypes can it theoretically produce with respect to these three loci?

In the late 1800s,Mendel defined two fundamental laws of transmission genetics;these were subsequently used to establish chromosome theory as scientists examined visible chromosomes in meiotic cells.Define these two laws,and diagram where in the process of meiosis these two processes actually occur.

The following pedigree shows the inheritance of a mild,but very rare condition in Siberian Husky dogs.If individuals 1 and 2 are crossed,what is the probability that they will produce an affected pup?

The Genetics Revolution

Independent Assortment of Genes

Mapping Eukaryote Chromosomes by Recombination

The Genetics of Bacteria and Their Viruses

Gene Interaction

Dna: Structure and Replication

Rna: Transcription and Processing

Proteins and Their Synthesis

Gene Isolation and Manipulation

Regulation of Gene Expression in Bacteria and Their Viruses

Regulation of Gene Expression in Eukaryotes

The Genetic Control of Development

Genomes and Genomics

The Dynamic Genome: Transposable Elements

Mutation, Repair, and Recombination

Large-Scale Chromosomal Changes

Population Genetics

The Inheritance of Complex Traits

Evolution of Genes and Traits

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