BIO 404 Genetics Exam 2
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1) Select the true statements about dominant and recessive genes. Circle all that apply. (2.5)
a) For a trait to be dominant at least one parent will show the trait.
b) For a trait to be recessive at least one parent will show the trait.
c) If both parents show a recessive trait, then all their offspring will typically show the trait too.
d) A trait in which unaffected parents produce affected offspring is probably recessive.
e) For a trait that has a dominant and a recessive allele, both the homozygous dominant and the heterozygote will show the dominant phenotype.
2) A white spotted bee-eater mates with a blue spotted bee-eater and the offspring have both blue and white spots. Which of the following could be an explanation of this? Circle all that apply. (1)
a) It is a qualitative trait with codominant alleles.
b) Epistatic genes are at work.
c) The trait is allelopathic.
d) The trait of spot color(s) shows quantitative inheritance.
3) In the venomous flying pit viper of inner Outer Mongolia, one pair of genes codes for stripe color. Homozygotes for one allele have red stripes; homozygotes for the other allele have blue stripes; if the trait shows incomplete dominance, what would be the expected result for the offspring? (.5) (pick one)
a) All the offspring would have purple stripes.
b) Half the offspring would have red stripes and half would have blue.
c) All the offspring would have red stripes but would carry the allele for blue.
d) Offspring would have both red and blue stripes.
4) A lesser red-footed roadrunner is homozygous dominant for red feet but only 75% of her offspring show this dominant trait. What does this indicate about the trait? (.5) (pick one)
a) The genes show conditional recessivity. b) The genes have low expressivity.
c) The genes show incomplete penetrance. d) The trait is of high heritability.
How are codominance and incomplete dominance a) alike on a cellular/genetic level? b) different on a phenotype level? (1)
Select the true statements about qualitative and quantitative traits. Circle all that apply. (2)
a) In incomplete dominant or codominant traits with two alleles, there will be three possible phenotypes.
b) Qualitative traits are more likely to be affected by environmental factors than quantitative.
c) Quantitative traits tend to show a range of phenotypes.
d) Qualitative traits can be influenced by modifying genes.
7) Based on Mendel's First Law, the Principle of Segregation, the gametes of a heterozygote will be: (.5)
a) 50% heterozygous, 50% homozygous b) 100% dominant
c) 75% dominant, 25% recessive d) 50% dominant , 50% recessive
8) Which of the following are possible ways a dominant lethal allele can still be passed on to offspring? (Circle all that apply.) (2)
a) The allele shows incomplete penetrance. b) The allele doesn't express until later in life.
c) The allele is lethal only if homozygous. d) The allele shows high heritability.
9) How does the Principle of Independent Assortment (Mendel's Second Law) relate to different gene pairs and gamete formation? How do syntenic genes and linkage not fit this principle? How could this principle be better stated? (1.5)
BIO 404 Exam 2 p.2
10) You are a world famous genetic counselor. A couple comes to you after giving birth to a son with hemophilia (which is a sex-linked trait). They also have a six-year-old daughter and four-year-old son that are phenotypically normal. Both parents are phenotypically normal. (2.5) Using a Punnet Square, answer each of the following:
What are the parents' genotypes?
What does this mean in regard to the daughter's genes?
What are the chances of their four-year-old son passing hemophilia to his children in the future?
What is their likelihood of producing another child with hemophilia?
11) In mammals, which parent determines the sex of the offspring? (.5)
12) The disease phenylketonuria is a genetic disease that causes mental retardation, small head, abnormal urine, and light skin and hair, due to the inability to metabolize phenylalanine in food. This information indicates the disease is: (pick one) (.5)
a) dominant b) lethal c) pleiotropic d) incompletely penetrant
13) Which of the following blood transfusions would be compatible? Circle all that apply. (1)
a) A donor, AB recipient b) O donor, B recipient c) AB donor, O recipient d) AB donor, A recipient
14) Explain what happens when an incompatible blood transfusion is given and why this occurs. (1)
15) Why are most lethal alleles are recessive? How would this relate to evolution? (1)
16) What are two factors that can affect expressivity or penetrance? (1)
A daughter shows a sex-linked recessive trait. Which of the following sets of parents could produce the affected daughter? (Circle all that apply) (1)
a) Carrier father (XNYn) carrier mother (XNXn)
b) Affected father (XnY0), and mother (XnXn)
c) Affected father (XnY0), carrier mother (XNXn)
d) Carrier father (XNXn), affected mother (XnXn)
Males are referred to as hemizygous for sex-linked genes. What does this mean? (1)
BIO 404 Exam 2 p.3
What is the difference between how modifying genes and epistatic genes affect other genes? Give an example of an epistatic gene. (1)
What are two ways in which modifying genes could affect the expression of a genetic disease? (1)
Select the true statements about sex chromosomes and sex-linked genes. Circle all that apply. (3.5)
a) The Y chromosome only contains genes for "maleness".
b) The presence of two X chromosomes will cause the development of the female phenotype, even if a Y chromosome is present, as in Klinefelter's syndrome.
c) In mammals, the father has no effect of the sex-linked (X linked) traits of his sons.
d) In mammals, the father has no effect of the sex-linked (X linked) traits of his sons.
e) Barr body formation (X inactivation) occurs prior to birth.
f) A Barr body is formed by an inactive X chromosome in normal females but isn't found in normal males.
g) Due to Barr body formation, some cells in a female may express an abnormal sex-linked recessive trait, yet her overall phenotype can be the normal dominant.
22) BONUS Calico cats are normally female. How would it be possible for a male cat to be calico (aside from an interesting dye job)?
23) Which one of the following could result in hemolytic disease of the newborn (hydrops fetalis, erythroblastosis fetalis)? (.5)
a) Rh- mom/Rh+ baby b) Rh- mom & baby c) Rh+ mom & baby d) Rh+ mom/Rh- baby
24) Why are the X and Y-chromosomes are not considered complementary? (1)
25) What do HLA genes code for? How does this relate to the function of the immune system? How does it relate to organ transplants? (1.5)
Select the true statements about sex influenced and sex limited traits: (circle all that apply) (2)
a) Sex limited traits are only expressed in one sex, but both sexes carry genes for them.
b) Sex influenced traits and sex limited traits are autosomal.
c) Sex influenced traits are only inherited from the mother.
d) Sex influenced traits will express differently in the different sexes.
A normal heterozygous father and a mother with cystic fibrosis would have what chance of producing a child with cystic fibrosis (an autosomal trait)? Use a Punnet Square as part of your answer. (1.5)
BIO 404 Exam 2 p.4
28) Why is Y monosomy lethal? (.5)
a) Lethal genes on the Y must be masked by genes on the X.
b) All forms of monosomy, whether of sex or autosomal chromosomes, are lethal.
c) The missing sex-linked genes on the X chromosome are essential to survival.
d) Y monosomy is not lethal.
29) What is a teratogen? Give two examples. (1.5)
30) What are three ways in which the phenotype of an individual can be affected by environmental factors after birth? (1.5)
31) Select the true statements about gender development of the embryo. Circle all that apply. (2)
a) Initially an embryo is "gender neutral"; the presence of the Y chromosome triggers male development; absence of the Y chromosome triggers female development.
b) The Y chromosome only contains genes specific for "maleness" traits.
c) Loss of part of the Y chromosome during meiosis may result in a female phenotype of the offspring resulting from that sperm.
d) Homosexuality has been found to have a genetic component.
32) Genetic heterogeneity means (pick one): (.5)
a) the variation of genes within a species or population.
b) a given genotype resulting in more than one phenotype.
c) different genes can produce phenotypes that appear the same.
d) Offspring show genetic variation due to crossing over of chromosomes.
33) BONUS What is genomic imprinting? Give an example.
34) Graft vs. host disease results when donated bone marrow cells actually attack the bone marrow recipient. Why does this happen? (1)
35) BONUS You have been asked to give expert testimony in a case where three sets of parents each claim to be the biological parents of a child who has just inherited several million dollars from her deceased adoptive parents. Blood typing has proven inconclusive. After the brilliant work you did in that hospital mix-up involving the four babies, your reputation as a phenomenal geneticist is again on the line. You run HLA gene identification on the girl and the couples for two HLA gene pairs, with the following results:
Child: HLA-A gene pair: alleles A2,A22; HLA-B gene pair: alleles B5,B37
Couple 1: Mom = A2,A6: B5,B12/ Dad=A6,A26;B12,B20
Couple 2: Mom = A2,A17; B11,B37/ Dad = A5,A9; B4,B10
Couple 3: Mom = A2,A8; B3,B36/ Dad = A14,A22; B5,B30
Assuming there has been no mixing of the couples (i.e. dad 1 and mom 2) or infidelity, what can you conclude about this child's parents? Why?