Exam 1

Marfan syndrome is an autosomal dominant disorder caused by a mutation of the FBN1 gene that affects the connective tissue of the body. Suppose that the two parents, a father with genotype fbn1 fbn1 and a mother with genotype FBN1 fbn1, are planning to have a family. What is the probability that they will have an affected daughter as their first child?

.25

Dominance

Two alleles of one gene are responsible for eggplant color, which can be purple and white One allele masks the effect of another allele

Incomplete dominance

Two alleles of one gene are responsible for eggplant color, which can be purple, lavender, and white

In cucumbers, dull fruit (D) is dominant over glossy fruit (d), orange fruit (R) is dominant over cream fruit (r), and bitter cotyledons (B) are dominant over nonbitter cotyledons (b). The three characters are encoded by genes located at different pairs of chromosome. A plant homozygous for dull, orange fruit and bitter cotyledons is crossed with a plant that has glossy, cream fruit and nonbitter cotyledons. The F1 are intercrossed to produce the F2. What is the probability that one of the F2 offspring will have a dull, orange, and nonbitter phenotype OR a glossy, orange and bitter phenotype?

0.28

The allele Y in Drosophilia is a dominant allele that is lethal when homozygous, but gives flies a yellow body color in the heterozygous condition with y, an allele for wild-type (brown) body color. At a second locus, the allele B for long bristles is incompletely dominant to the allele b for short bristles. Both loci are autosomal. If you cross 2, yellow body, medium bristled flies with each other, what is the probability that one of the living offspring will have the same phenotype as the parents?

0.33

Suppose two parents, a father with genotype AaBbCcDdee and a mother with the genotype aaBbCCDdEe, wanted to have children. Assume each locus follows Mendelian inheritance patterns for dominance. What proportion of the offspring will have each of the following characteristics? 1. same genotype as the father 2. same genotype as the mother 3. phenotypically resemble the father 4. phenotypically resembe the mother

1. 0.03125 2. 0.03125 3. 0.141 4. 0.141

Polydactyly (PD) is an autosomal dominant trait (polydactyly=P; wildtype=p). Cystic fibrosis (CF) is an autosomal recessive trait (cystic fibrosis=f; wildtype=F). A PD woman, otherwise normal in phenotype, marries a healthy normal man. Their 4 children are 1) normal, 2) PD, 3) CF, 4) CF+PD. What is the probability that their 5th child will have AT LEAST ONE of these conditions? 1. What is the probability the child will be PD? 2. What is the probability the child will have cystic fibrosis? 3. What is the probability the child will have PD AND cystic fibrosis? 4. What is the overall probability that the child will have at least one of these conditions?

1. 0.50 2. 0.25 3. 0.13 4. 0.63

An albino (autosomal, recessive) female human with normal vision and phenotypically normal parents has a non-albino brother who is colorblind (X-linked, recessive). She marries a phenotypically normal male human who knows he is a carrier for albinism. What is the probability that their child will be phenotypically norma? 1. What is the probability that the female is a carrier for colorblindness? 2. If the female IS a carrier, and she and the male have a child together, what is the probability that it will be phenotypically normal? 3. If the female is NOT a carrier, and she and the male have a child together, what is the probability that it will be phenotypically normal? 4. What is the overall probability that the child will be phenotypically normal?

1. 0.50 2. 0.38 3. 0.50 4. 0.44

Suppose a particular species of tulip plant has three alleles for the gene that codes for flower color. The C^R allele produces red tulips, the C^p allele produces purple tulips, and the C^w allele produces white tulips. C^r is dominant over C^p and C^w, and C^p is dominant over C^w. For each of the following crosses, determine the expected ratio of offspring for each flower color. 1. C^RC^p x C^pC^w 2. C^RC^W x C^PC^W

1. 2 red: 2 purple: 0 white 2. 2 red: 1 purple: 1 white

Suppose two independently assorting genes are involved in the pathway that determines fruit color in squash. These genes interact with each other to produce the squash colors seen in the grocery store. At the first locus, the W allele codes for a dominant white phenotype, whereas the w allele codes for a colored squash. At the second locus, the allele Y codes for a dominant yellow phenotype, and the allele y codes for a recessive green phenotype. The phenotypes from the first locus will always mask the phenotype produced by the second locus if the dominant allele (W) is present at the first locus. This masking pattern is known as dominant epistasis. A dihybrid squash, WwYy, is selfed, and produces 320 offspring. How many offspring are expected to have each of the following phenotypes? 1. White 2. Yellow 3. Green

1. 240 2. 60 3. 20

You have crossed two black labs that are both BbEe genotypes, and the resulting litter consists of 15 black, 4 brown, and 6 yellow labs. You conduct an X^2 test of the null hypothesis that the offspring match the expected ratio for recessive epistasis, and any difference are due to chance. The X^2 value you calculate is 0.190. 1. How many yellow labs do you expect? Answer to one decimal place. 2. What are your degrees of freedom? 3. What is the corresponding critical value from the X^2 table? Answer to 3 decimal places. 4. Do you reject or fail to reject the null hypothesis?

1. 6.3 2. 2 3. 5.991 4. Fail to reject, because the X^2 value is less than the critical value

Colorblindness is a sex-linked recessive trait. A female is colorblind in one eye, but not both. 1. Select the explanation for this condition. a. female has XO genotype b. all X chromosomes are inactivated c. random X-chromosome inactivation 2. Is it possible for a male to have different color-blindness phenotypes in each eye? a. no, since XXY males lack X-chromosome inactivation b. yes, in an XXY male with a different active X in each eye c. yes, in an XYY male with a different active Y in each eye d. no, trisomy of the sex chromosomes is lethal

1. c 2. b

A homozygous variety of opium poppy (Papaver somniferum Laciniatum) with lacerate leaves was crossed with another homozygous variety with normal leaves. All the F1 had lacerate leaves (jagged-edged leaves). Two F1 plants were crossed to produce the F2. Of the F2, 249 had lacerate leaves and 16 had normal leaves. 1. How are lacerate leaves determined in the opium poppy? 2. Give the genotype(s) for the P generation. 3. Give the genotype(s) for the F1 generation. 4. Give the genotype(s) for the F2 (lacerate) generation. 5. Give the genotype(s) for the F2 (normal) generation.

1. two genes, with a dominant allele at either or both loci 2. AABB & aabb 3. AaBb 4. A_B_, aaB_, & A_bb 5. aabb

Bread wheat (Triticum aestivum) is a hexaploid organism with 42 chromosomes (6n=42). After meiosis is complete, how many chromosomes will be present in a single pollen grain?

21

Primula burmanica is 2n=44. How many homologous pairs are present at prophase of mitosis? Note that chromosomes do not have to be physically next to each other to be a part of a homologous pair, they just need to be homologs in the same nucleus.

22

The annual sunflower (Helianthus annuus) has a diploid chromosome number of 2n=34. How many chromatids are there in a single cell at metaphase 2 of meiosis?

34

Both Mitosis and Meiosis

Duplication of chromosomes occurs before cell division

Meiosis

Forms four haploid gametes Contributes to genetic diversity through crossing over

Mitosis

Results in two diploid cells identical to the parent cell Used for asexual reproduction

Epistasis

The allele of one gene mask the effect of another gene

Codominance

The heterozygous phenotype has both homozygous phenotypes equally expressed Two alleles of one gene are responsible for eggplant color, which can be purple and white patches, purple, and white

An individual possesses two alleles at a locus and these two alleles separate when gametes are formed, one allele going into each gamete. This genetic concept is known as which of the following? a. principle of segregation b. chromosome theory of heredity c. concept of dominance d. reciprocal cross e. principle of independent assortment

a

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these 2 characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2. If an F1 plant is backcrossed with the bitter, yellow-spotted parent, what phenotypes and proportions are expected in the offspring? a. all bitter fruit with yellow spots b. all sweet fruit with no spots c. 1/4 bitter fruit, yellow spots; 1/4 bitter fruit, no spots; 1/4 sweet fruit, yellow spots; and 1/4 sweet fruit, no spots d. 1/2 bitter fruit, yellow spots and 1/2 sweet fruit, no spots e. 9/16 bitter fruit, yellow spots; 3/16 bitter fruit, no spots; 3/16 sweet fruit, yellow spots; and 1/16 sweet fruit, no spots

a

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these 2 characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2. What will be the phenotypic ratio in the F2? a. 9/16 bitter fruit, yellow spots; 3/16 bitter fruit, no spots; 3/16 sweet fruit, yellow spots; and 1/16 sweet fruit, no spots b. 1/4 bitter fruit, yellow spots; 1/4 bitter fruit, no spots; 1/4 sweet fruit, yellow spots; and 1/4 sweet fruit, no spots c. all sweet fruit with no spots d. 1/2 bitter fruit, yellow spots and 1/2 sweet fruit, no spots e. all bitter fruit with yellow spots

a

Phenylkentonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that an egg from the mother will contain the PKU allele? a. 1/2 b. 2/3 c. 1/3 d. 3/4 e. 1/4

a

Sister chromatids have all of the following features except that: a. two chromatids attached at the centromere are considered a homologous pair b. they will separate at anaphase of mitosis or anaphase 2 of meiosis c. they have telomeres on each end d. they are attached at the centromere

a

What term describes an individual possessing two of the same alleles at a gene locus? a. homozygous b. heterozygous c. wild type d. monohybrid e. dihybrid

a

You are testing the null hypothesis that the outcome of a dihybrid cross conforms to a 1:1:1:1 ratio resulting from a cross between a heterozygous individual (AaBb) and a homozygous recessive individual (aabb), and that any differences are due to chance. Your calculated X^2 value is 5.721. Do you reject or fail to reject your null hypothesis? Assume a significance cut-off of P< 0.05. a. fail to reject, because the x^2 value is less than the critical value b. Reject, because the x^2 value is greater than the critical value c. Fail to reject, because the x^2 value is greater than the critical value d. Reject, because the x^2 value is less than the critical value

a

At the end of your biology class; your professor asks you to develop a project to determine the genotype of a plant with red flowers. Red petal color (R) is dominant to pink flower color (r). To accomplish this task, you cross the plant with the unknown genotype with heterozygous red-flowered plants. Which of the following are valid predictions of the ratio of flower colors in the offspring? a. 3 red:1 pink flowers b. all red flowers c. 1 red: 3 pink flowers d. all pink flowers

a & b

Which of the following will tend to lose genes over evolutionary time due to sex chromosome degeneration? a. W chromosome (birds) b. Y chromosome (mammals) c. X chromosome (mammals) d. Z chromosome (birds)

a & b

When conducting his initial experiment, Gregor Mendel chose the pea plant as his research organism. He began conducting his genetic research on pea plant traits such as plant height, seed color, and seed shape. He started by using true-breeding, or pure-breeding, lines of pea plants. Select the characteristics of a true-breeding plant line. a. in most cases, is homozygous for the trait of interest b. always contributes recessive alleles to offspring c. when selfed, all of the offspring show the trait of interest d. always contributes dominant alleles to offspring

a & c

Genomic imprinting occurs when gene expression in the offspring depends upon whether a particular allele was inherited from the mother or the father. Which of the following statements is likely to explain the evolutionary basis for the existence of imprinting? a. sexual selection favors opposite characteristics in males and females. For example, a deep voice decreases a human female's chances of finding a mate, but does not harm a male's chance. Therefore, the gene for deep voice is expressed when inherited from the father and not when inherited from the mother. b. the ideal reproductive strategy is different for males and females. For example, maximum birth weight and fetal growth are favored by fathers because they increase offspring survival. Mothers favor maternal survival and the preservation of resources for future reproduction. Therefore, a mother may benefit from reduced fetal growth rates. c. Strong maternal attachment is favored in mothers, and strong paternal attachment is favored in fathers. Therefore, offspring that inherit a gene for paternal attachment from their mother will not express the gene. Likewise, offspring that inherit a gene for maternal attachment from their father will not express the gene. d. Sex-linked traits are more likely to affect males than females. Therefore, if a trait is beneficial, it may be expressed only when inherited from the father. Both beneficial and harmful traits may be expressed when inherited from the mother.

b

In a case of a number of bird species, the male is homogametic rather than the female. This means that: a. a ZW individual is male b. a ZW individual is female c. A ZZ individual is female d. a ZW individual is monoecious e. a ZZ individual is monoecious

b

In mammals, why is the aneuploidy of the X chromosome more often viable than aneuploidy of the autosomes? a. feedback inhibition limits the expression of X-linked genes. Therefore, additional copies of X-linked genes do no result in increased concentrations of gene product b. in mammals, only one homolog of the X chromosome remains active. More or all of the genes on any additional X chromosomes are inactivated c. the X chromosome contains far fewer genes than any autosomes, and most X-linked genes affect only reproduction, not survival d. mammals are less sensitive to the doses of X-linked gene products than they are to the doses of autosomal gene products

b

Of the following sex chromosome aneuploidy conditions, which demonstrates that a single X chromosome is sufficient for human development and survival? a. XXY b. XO c. XXX d.XYY

b

Phenylkentonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that a sperm from the father will contain the PKU allele? a. 2/3 b. 1/2 c. 3/4 d. 1/3 e. 1/4

b

Phenylkentonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that their next child will be heterozygous for the PKU gene? a. 1/4 b. 1/2 c. 3/4 d. 1/3 e. 2/3

b

Phenylkentonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that their next child will have PKU? a. 2/3 b. 1/4 c. 1/3 d. 1/2 e. 3/4

b

With the genic sex-determination mechanism, which of the following statements is true? a. females have two X chromosomes and males have on (XO) b. Sex is determined by genes on undifferentiation chromosomes c. females have one Z and one W (ZW) and males have two Z chromosomes (ZZ) d. sex is determined by environmental factors e. females have two x chromosomes (XX) and males have on X and one Y chromosome (XY)

b

X-linked red-green color blindness in humans is a recessive condition. Which of the following statements is true? a. a colorblind man must have a colorblind mother b. a colorblind woman must have a colorblind father c. a colorblind woman must have a colorblind mother d. a colorblind man must have a colorblind father e. a man with normal vision cannot have a colorblind father

b

Extranuclear inheritance, including mitochondrial and chloroplast inheritance, occurs in eukaryotes when genetic information is transmitted by means other than through nuclear DNA. Select the examples of mitochondrial or chloroplast inheritance. a. mental retardation in humans occurs because of trinucleotide repeats in an X chromosome region b. slow growth in Neospora occurs because of a mutation that inhibits ATP synthesis c. white leaves in Mirabilis jalapa are caused by a mutation that affects chlorophyll production d. commercial banana plants produce seedless fruits because the plants are triploid

b & c

In butterflies, sex is determined by the ZW sex-determination system. Female butterflies are heterogametic and have both a Z sex chromosomes and a W sex chromosome for sex determination. In contrast, male butterflies are homogametic and have two Z sex chromosomes. Select all of the relatives from which a female butterfly could have inherited her Z sex chromosome. a. mother b. paternal grandmother c. maternal grandfather d. father

b & c

What process(es) unique to meiosis is/are responsible for genetic variation and at what point in meiosis do(es) each occur? a. condensation of homologous chromosomes during prophase 1 b. random alignment and separation of homologs that takes place during metaphase 1 and anaphase 1, respectively c. independent assortment of homologs that takes place during anaphase 2 d. crossing over of non-sister chromatids that takes place during prophase 1

b & d

Which of these choices describe Y-linked traits? a. a carrier female has a 25% chance of having a carrier daughter b. the phenotype is solely expressed in males c. males have a higher probability of inheriting the trait from their mother d. female offspring cannot inherit the trait e. females have a greater probability of being a carrier of the trait

b & d

A gene whose expression is affected by epigenetic tags based on the sex of the transmitting parent demonstrates which of the following? a. genetic maternal effect b. anticipation c. genomic impriniting d. pleiotropy e. epistasis

c

In humans, oculocutaneous (OCA) albinism is a collection of autosomal recessive disorders characterized by an absence of the pigment melanin in skin, hair, and eyes. That is, normal pigmentation (A) is dominant over albinism (a). For this question, assume it is a single gene with 2 alleles. If both parents display the albino phenotype, what possible phenotypes may be observed in their offspring? a. normal pigmentation only b. marbling of albino and normal pigmentation c. albinism only d. normal pigmentation or albinism

c

Snapdragons occur in nature as either green- or yellow-leaved plants. Suppose that a gardener crosses two yellow-leaved snapdragons, and one-third of the offspring have green leaves while two-third of the offspring have yellow leaves. What is the most likely explanation for this outcome? a. the allele causing yellow leaves is carried in the chloroplast genome b. the allele causing yellow leaves is a dominant lethal allele c. the allele causing yellow leaves is a recessive lethal allele d. the allele causing yellow leaves is a recessive epistatic allele

c

Suppose in a species of petunia, locus A determines petal color and locus B determines whether the petals can express any pigment. At locus A, purple petal color (A) is dominant over yellow petal color (a). At locus B, pigmentation (B) is dominant over lack of pigmentation (b). If an AABB plant is crossed to an aabb plant, what is the ratio of purple- to yellow- to white-flowered petunias expected in the F2 progeny? a. 12:3:1 b. 15:1 c. 9:3:4 d. 9:4:3 e. 9:7

c

Which statement below defines epistasis? a. a measurement of phenotype intensity b. a heterozygote displays a phenotype intermediate between its two alleles c. when one gene influences or masks the effect of another gene d. when a single gene affects several phenotypes

c

You cross a curly-winged female fruit fly with a straight-winged male fruit fly and get all straight-winged females and all curly-winged males. The next month you repeat the cross, this time using a curly-winged male fruit fly and a straight-winged female and get all straight-winged offspring. Assume the starting parents in each cross are true-breeding. What is the mode of inheritance for the allele controlling curly wings in fruit flies? a. mitochondrial b. autosomal- straight recessive to curly c. X-linked- curly recessive to straight d. autosomal-curly recessive to straight e. X-linked-straight recessive to curly

c

You cross a round-seeded pea plant that is heterozygous for the allele controlling seed shape (Rr) with a true-breeding wrinkled pea plant (rr). There are 73 round and 127 wrinkled offspring. The null hypothesis is that the cross conforms to the expected ration of an Rr x rr cross with one dominant (R) and one recessive (r) allele. Do you reject or fail to reject the null hypothesis? Assume a significance cut-off of p<0.05. a. Cannot determine based on the data provided b. fail to reject c. reject

c

A man and a woman are both deaf, and deafness is a recessive, autosomal trait. However, when they have a child together, it has normal hearing. What could explain the fact that two deaf parents could have a child who is not deaf? a. codominance b. this outcome is not possible; you cannot cross two recessive individuals and recover a dominant phenotype c. incomplete dominance d. complementation

d

A yellow female Labrador retriever was mated with a brown male. Half of the puppies were brown, and half were yellow. Explain how the same female, when mated with a different brown male, could produce only brown offspring. a. the first male was bbEe, and the second male was BbEe b. the first male was bbEe, and the second male was bbee c. the first male was bbEE, and the second male was bbEe d. the first male was bbEe, and the second male was bbEE e. the first male was BbEE, and the second male was BbEe

d

Achondroplasia is a common cause of dwarfism in humans. All individuals with achondroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with achondroplasia mate, the offspring occur in a ratio of 2 achondroplasis: 1 normal. What is the most likely explanation for these observations? a. achondroplasia is codominant to the normal condition b. achondroplasia is incompletely dominant to the normal condition c. the allele that causes achondroplasia is a dominant lethal allele d. the allele that causes achondroplasia is a recessive lethal allele

d

Cell division by mitosis is a mechanism of asexual cell replication. Some single-cell organisms reproduce by cell division, and cell division enables multicellular organisms to grow and repair damaged cells. Which of the following are products of cell division by mitosis? a. daughter cells with half the number of chromosomes b. cells that have different forms of the same gene c. four daughter cells that are genetically the same d. two daughter cells with identical chromosomes

d

Earthworms contain ovaries in one segment and testes in another segment of their body. Which term describes the sex system of the organism? a. XO sex determination b. XY sex determination c. ZW sex determination d. monoecious e. dioecious

d

If an Aa individual is crossed to an aa individual, what will be the phenotypic ratio in the offspring? a. 2:1 b. 4:0 c. 1:1:1:1 d. 1:1 e. 3:1

d

In chickens the females are heterogametic, ZW, and the males are homogametic, ZZ. Most sex-linked genes are only carried on the Z chromosome. Congenital baldness is caused by a recessive sex-linked allele. If a bald male is crossed to a normal female, what would be the expected results in the offspring? a. half the offspring will be bald and half will be normal regardless of sexual phenotype b. all the females will be normal and all the males will be bald c. all the offspring will be bald regardless of sexual phenotype d. all the males will be normal and all the females will be bald e. all the offspring will be normal regardless of sexual phenotype

d

In the Dorset sheep breed, both males and females have horns, and the trait is controlled by an autosomal gene. When true-breeding Dorset sheep are crossed with true-breeding hornless sheep, all the F1 males have horns and the F1 females are hornless. If two of these F1 sheep were intercrossed, what ratio of horned to hornless female sheep do you expect in the F2 generation? a. all hornless b. 3 horned: 1 hornless c. all horned d. 1 horned: 3 hornless

d

In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are dominant over no spots (s). The genes for these 2 characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2. If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring? a. all bitter fruit with yellow spots b. all sweet fruit with no spots c. 1/2 bitter fruit, yellow spots and 1/2 sweet fruit, no spots d. 1/4 bitter fruit, yellow spots; 1/4 bitter fruit, no spots; 1/4 sweet fruit, yellow spots; and 1/4 sweet fruit, no spots e. 9/16 bitter fruit, yellow spots; 3/16 bitter fruit, no spots; 3/16 sweet fruit, yellow spots; and 1/16 sweet fruit, no spots

d

Multiple sclerosis (MS) is controlled by multiple autosomal loci, making it a complex disease to understand and treat. One interesting fact about the disease is that when one twin in a set of genetically identical twins develops MS, there is only a 25% chance that the other twin will also develop MS. This is an examples of: a. variable expressivity b. x-inactivation c. variable penetrance and expressivity d. variable penetrance

d

The white-eyed mutation in Drosophilia studied by Thomas Hunt Morgan was the first clear case of sex-linked inheritance. When Morgan crossed a white-eyed female with a red-eyed male, what phenotypes were present in the offspring? a. all the offspring had white eyes b. all the females had white eyes and all the males had red eyes c. one half of both females and males had red eyes and one half had white eyes d. all the males had white eyes and all the females had red eyes e. all the offspring had red eyes

d

Two unlinked genes control unicorn coat color. You cross a true-breeding purple unicorn with a true-breeding blue unicorn and all the F1 offspring are purple. Intercrossing these F1 individuals yields the following ration of offspring: 3 teal: 3 red: 1 blue. What type of gene interaction does this represent? a. variable expressivity b. incomplete dominance c. dominant epistasis d. additivity e. codominance

d

What information can the chi-square goodness-of-fit test provide? a. that the results of the genetic cross are correct b. the genotypes of the two parents in the test cross c. how well the genetic cross was carried out d. how well the observed results of a genetic cross fit the expected values e. the genotypes of the progeny in the test cross

d

Which of the following statements accurately describes both pleiotropy and polygenic inheritance? a. polygenic inheritance refers to the effect of a single gene on a single trait. Pleiotropy refers to a single gene that affects multiple trait. b. polygenic inheritance refers to a single gene that affects multiple traits. pleiotropy refers to the cumulative effect of two or more genes on a single trait c. polgenic inheritance refers to the cumulative effect of two or more genes on a single trait. pleiotropy refers to a single gene that affects a single trait d. polygenic inheritance refers to the cumulative effect of two or more genes on a single trait. Pleiotropy refers to a single gene that affects multiple traits

d

Penile hypospadias, a birth defect in male humans in which the urethra opens on the shaft instead of at the tip of the penis, results from an autosomal dominant gene in some families. Females who carry the gene show no effects. What type of trait is this birth defect an example of? a. a sex-influenced trait because the defect occurs only in males and the gene involved is autosomal b. a genetic maternal effect because the presence of the trait depends upon the genotype of the mother c. an X-linked trait because the defect occurs more often in males than in females d. a Y-linked trait because the defect occurs only in males e. a sex-limited trait because the defect occurs only in males and the gene involved is autosomal

e

What is the physical appearance or manifestation of a characteristic called in genetics? a. wild type b. alleles c. independent assortment d. genotype e. phenotype

e