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PCB3063 Module 3
Terms in this set (47)
Compared to standard mendelian inheritance patterns, what do codominance, partial dominance, lethal Alleles, and epistasis have in common?
They alter phenotypic ratios
Which type of hemoglobin molecules are produced by an individual who is a heterozygous carried for Sickle Cell Disease?
50% of the hemoglobin has the standard shape and 50% of the hemoglobin has the altered shape
A homozygous dominant genotype for gene A prevents the expression of gene B. Which gene is epistatic?
A mutation that creates a completely nonfunctional gene variant is called an __________ allele.
If a white-eyed female drosophila is crossed with a red-eyed male, which offspring are expected?
All female offspring have red eyes; all male offspring have white eyes
What does the term multiple alleles mean?
There are more than two possible alleles for one gene in a population
The expression fo some autosomal genes can be influencced by the sex of the organism. In particular, some gemes are expressed more strongly (but not exclusively) in one sex. What is this called?
How are new alleles formed?
Which of the following characteristics is not influenced by genes with multiple alleles?
A trait is known to exhibit codominance. Two heterozygous organisms are crossed (Aa x Aa). What is the phenotypic ratio?
An individual whose blood type is AB marries someone whose blood type is O. Which phenotypes/blood types would you expect among their offspring?
Blood type A and blood type B
What term describes the phenotype most commonly found in a population?
A true breeding black rodent is crossed with a true breeding white rodent. All of the offspring are speckled black and white.
Which inheritance pattern is represented?
What is the genotype of people with delayed onset Huntington's Disease?
Red-green color blindness and __________ are known to be inherited as X-linked recessive traits.
A dihybrid cross produced a 9:3:4 ratio. What does this ratio suggest?
Which inheritance pattern is not a component in the inheritance of blood types in humans?
What term is used to indicate the alternative forms of genes?
Purple is the wild type color in a certain flower. Two white mutants are crossed, and all resulting offspring are purple. Which phenomenon is being exhibited?
Polydactyly is the presence of extra digits (extra toes and fingers). Many individuals have the genotype for polydactyly, but they do not develop extra digits. Whcih inheritance princliple is this?
Ebony body color in the fruit fly is considered a recessive mutant phenotype. What is the associated genotype of ebony fruit flies?
The phenomenon in which a single gene influences the development of many phenotypes is called ________.
How many different phenotypes are possible in a one gene/three allele system that displays codominance to each other
Which of the following is the most likely example of codominance?
A pure-breeding plant with red flowers is crossed to a pure breeding plant with white flowers. All their progeny have flowers with some red patches and some white patches
True or False: The color dilution gene in horses it an example of incomplete dominance
If Jane and John want to have another child, they plan to see a genetic counselor to find out when it would be best to test for galactosemia. A newborn with galactosemia must be put on a lactose- and galactose-free diet as soon as possible after birth. Even on this diet, affected individuals may still suffer from learning disabilities, ovarian failure (in young women), late-onset cataracts, and early death.
Which of the following tests would be most useful for Jane and John to have?
Newborn screening (either assaying for the GALT enzyme or measuring excess galactose in the newborn's blood)
White eye color is an X-linked trait in one line of fruit flies. White eyes is recessive to red eyes. If a red-eyed female and white-eyed male are crossed...
Some of their male progeny may have white eyes - if female is heterozygous
True or False: or X-linked traits in Drosophila, the male phenotype is determined by the maternally inherited allele
Eye color in Drosophila is an X-linked trait. White eyes is recessive to red eyes. If a Drosophila male has white eyes, which of the following must also be true?
His mother has at least one white allele
Expression of the A and B antigens on red blood cells is influenced by the FUT1 gene. This gene encodes fucosyl transferase, an enzyme that helps produce the H substance. Which of the following statements about the H substance are correct?
The H substance is a substrate for the enzyme produced by the IA and IB genes. These enzymes add the appropriate terminal sugar to the substance producing the A and B antigens, respectively
Individuals that fail to produce the H substance are said to have the Bombay phenotype
Individuals that are heterozygous for the FUT1 gene can still produce the H substance
Individuaks that cannot produce the H substance appear to be type O even if they have functional IA and/or IB alleles
Studies of large human populations have determined that the penetrance of a particular PRSS1 mutation, Arg122His, is 86%.
What does this means for individuals with the predisposing genotype?
They have an 86% chance of showing the associated phenotype
Imagine that you are part of a research team interested in determining the penetrance of a different PRSS1 mutation, Ala16Val. Your team has identified 120 individuals with the PRSS1 Ala16Val allele and found that 48 of the individuals did not display any evidence of pancreatitis.
From your data, what is the penetrance of the PRSS1 Ala16Val mutation?
If a man who is heterozygous for a PRSS1 Ala16Val mutation mates with a woman who is homozygous for normal cationic trypsinogen, what is the probability that their offspring will have hereditary pancreatitis, given the penetrance value obtained in Part B?
Epistasis is the interaction between genes such that one gene influences or interferes with the expression of another gene, leading to a specific phenotype. Epistatic genes can be dominant or recessive. Use your knowledge of epistasis to determine the genotypes of offspring in the following crosses.
In freshwater snails, pigment color is influenced by two genes. If two heterozygous pigmented freshwater snails were crossed and offspring were produced in a ratio of 9 pigmented snails to 7 albino snails, what are the genotypes of the offspring?
Genotypes of pigmented snails = A_B_
Genotypes of albino snails = A_bb aaB_ aabb
Is snail pigmentation an example of dominant or recessive epistasis when the ratio is 9:7?
In sheep, coat color is influenced by two genes. Gene A influences pigment production, while gene B produces black or brown pigment.
If two heterozygous white sheep were crossed and offspring were produced in a ratio of 12 white sheep to 3 black sheep to 1 brown sheep, what are the genotypes of the offspring?
Genotypes of white sheep = A_B_ A_bb
Genotypes of black sheep = aaB_
Genotypes of brown sheep = aabb
Is sheep pigmentation an example of dominant or recessive epistasis when the ratio is 12:3:1?
In laborador retrievers, pigment color is influenced by two genes. Gene A determines the type of pigment produced and gene B affects whether the pigment gets deposited in the hair shaft.
If two heterozygous black laborator retrievers were crossed and offspring were produced in a ratio of 9 black dogs to 3 brown dogs to 4 yellow dogs, what are the genotypes of the offspring?
Genotypes of black dogs = A_B_
Genotypes of brown dogs = aaB_
Genotypes of yellow dogs = aabb A_bb
Is laborador retriever pigmentation an example of dominant or recessive epistasis when the ratio is 9:3:4?
Your mentor asks you to determine if the mutants belong to the same complementation group. What is true about flies that belong to the same complementation group?
They all have some mutation in the SAME wing-development gene. Each strain may have a different mutation, but the same gene is mutated in all strains in a complementation group
What would be the outcome of crossing two strains of wingless flies that belong to the same complementation group?
All offspring will be wingless
The trait appears about equally prevalent in males and females
The phenotype of the disease is seen in every generation
If an effected male mates with a normal female, then all daughters and no sons will be affected
If a normal male mates with a heterozygous female, then half of daughters and sons will be affected
The phenotype of the disease may skip generations
There is a greater prevalence of affected males
If an affected male mates with a normal female, then neither daughters nor sons will show the disease phenotype
If a normal male mates with a heterozygous female, then half of sons will be affected and daughters will nor show the disease phenotype
Although the vast majority of women who inherit a single copy of an X-linked recessive disease allele are not affected by the disorder, a small percentage of women do display the disease phenotype. Which of the following could explain this rare phenomenon?
Turner syndrome ( a sex-chromosome aneuploidy in which women have only one X-chromosome)
X-inactivation that favors inactivation of the normal X-chromosome
A mutation that causes a yellowing of leaves in snapdragon plants was discovered in the early 1900s. Plants with this condition, termed aurea, have less chlorophyll than green plants.
Crosses between various combinations of green and aurea plants yielded the following results.
green x green = all green
aurea x aurea = 2/3 aurea, 1/3 green
green x aurea = 1/2 green, 1/2 aurea
If the green allele is designated as G, and the aurea allele is designated as GA , assign genotypes to the phenotypes listed.
Hwo can the unusal results from the crosses be explained?
The aurea allele behaves as a recessive lethal allele
With respect to snapdragon color, what can be said of the G and GA alleles?
GA is dominant to the G allele
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