Genetics BIO 3709 exam review

1. Who was a nineteenth‑century biologist who put forth the theory of evolution through natural selection and published his idea in the book entitled On the Origin of Species?

e. Charles Darwin

1. Humans with only one sex chromosome (XO) usually have underdeveloped sexual characteristics and are sterile. What is this condition called?

e. Turner syndrome

1. What information can the chi‑square goodness‑of‑fit test provide?

e. how well the observed results of a genetic cross fit the expected values

1. In humans, what normally results in the male sexual phenotype?

e. the presence of the SRY gene on the Y chromosome

1. What happens during prophase I of meiosis?

f. Homologous chromosomes form and crossing over occurs between them

1. Which term describes the situation, for X‑linked genes, in human and Drosophila males who have only one X chromosome?

hemizygous

Use the Punnet Squares interactive, Level 3 to conduct a cross between a man with normal vision and a woman with the gene for color blindness. A man with normal vision, XB Y, and a woman who is a carrier for color blindness, XB Xb, mate. How many genotypes result in female offspring with normal vision? number of genotypes: What percentage of male offspring will be color‑blind? color‑blind male offspring: If the mother were color‑blind, what percentage of male offspring would be color‑blind? color‑blind male offspring:

the number of genotypes: 2 color‑blind male offspring: 50% color‑blind male offspring: 100%

Match the checkpoint to its function.

- G1/s checkpoint: maintains cell until necessary enzymes for replication are synthesized - G2/M checkpoint: detection of DNA damage after replication - Spindle-assembly checkpoint: ensures that each chromosome is attached to spindle fibers from opposite poles

In Caenorhabditis elegans, the level of expression of genes on both X chromosomes of females is reduced by half. What phenomenon is this an example of?

dosage compensation

What are checkpoints?

c. transition points during the cell cycle that ensure all cellular components are functioning properly

1. 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 two 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. 1. What will be the phenotypic ratio in the F2? 2. If an F1 plant is backcrossed with the bitter, yellow‑spotted parent, what phenotypes and proportions are expected in the offspring? 3. If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring?

1. 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 2. All bitter fruit with yellow spots 3. 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

Color blindness is a sex‑linked recessive trait. A female is color blind in one eye, but not both. 1. Select the explanation for this condition. 2. Is it possible for a male to have different color‑blindness phenotypes in each eye?

1. random X-chromosome inactivation 2. yes, in an XXY male with a different active X in each eye

1. The study of the chemical nature of the gene, and how genetic information is replicated and expressed, is part of what division of genetics?

c. population genetics

Use the karyotype interactive to answer the question. Identify the chromosomal disorders affecting the patients in the Abnormal Karyograms tab of the karyotype interactive. Place each patient according to whether his or her disorder occurs exclusively in biological males, exclusively in biological females, or in both sexes.

Affects only biological males = patient 892 Affects only biological females = patient 367 Affects both sexes = patient 768 - patient 251

The figure represents a pair of homologous chromosomes. Assign the appropriate term to each component.

BB = Homozygous dominant locus dd = homozygous recessive locus Nn = heterozygous locus

The somatic cell of a sheep contains 54 chromosomes54 chromosomes (2𝑛=54).(2⁢n=54). How many chromosomes and how many DNA molecules would the primary spermatocyte of this sheep have?

Chromosomes = 54 DNA molecules = 108

A man, Joe, has classic hemophilia, an X‑linked recessive disease. Classify each person depending on whether or not Joe could have inherited the hemophilia gene from him or her.

Could have inherited= Maternal grandmother , Maternal Grandfather Could not have inherited= Paternal grandmother, Paternal grandfather

Intracellular components can be labeled with a fluorophore, and the dynamic movements within the cell can be visualized. Arrange the images of the stages of cell division in order from interphase to cytokinesis.

Interphase- D-C-B-A-E- Cytokinesis

An autotriploid has three sets of homologous chromosomes in each cell instead of the usual pairs of homologous chromosomes present in diploid individuals. Calculate the number of chromosomes in a diploid cell, given an 𝑛=16.

Number of Chromosomes = 32

An autotriploid has three sets of homologous chromosomes in each cell instead of the usual pairs of homologous chromosomes present in diploid individuals. Calculate the number of chromosomes in an autotriploid cell, given an 𝑛=18.

Number of Chromosomes = 54

Classify whether each gene regularly exists in a hemizygous state.

Regularly hemizygous = A muscular dystrophy gene on the X chromosome in a normal human male. A transgenic gene inserted into only one chromosome of a mouse. Not regularly hemizygous = A muscular dystrophy gene on an X chromosome in a normal human female. A gene on chromosome 21 in an individual with Down syndrome

1. What is the mechanism by which sex is established?

a. sex-determination

In cats, curled ears result from an allele, Cu, that is dominant over an allele, cu, for normal ears. Black color results from an independently assorting allele, G, that is dominant over an allele for gray, g. A gray cat homozygous for curled ears is mated with a homozygous black cat with normal ears. All the F1 cats are black and have curled ears. What phenotypes and proportions are expected from the two crosses?

Two of the F1 cats mate = 9/16 black cats, curled ears; 3/16 black cats, normal ears; 3/16 gray cats, normal ears An F1 cats mates with a stray cat that is gray and possesses normal ears = 1/4 black cats, curled ears; 1/4 black cat, normal ears; 1/4 gray cats, curled ears; and 1/4 gray cats, normal ears.

Match each phenotype description to its corresponding sex chromosome genotype in humans.

XO with SRY on an autosome = phenotypically male but karyotype XY with SRY deleted = phenotypically female but karyotype indicates presence of both sex chromosomes. XXXX = phenotypically female with some abnormalities and overexpression of X chromosomes genes XXY = phenotypically male with sterility and hypogonadism XYY = phenotypically male with an increase in average stature

In Drosophila melanogaster, white eye is an X‑linked recessive trait, and red eye is an X‑linked dominant trait. Assume that the flies have a diploid set of autosomes (2A). Allele Xw codes for white eye, and allele X codes for red eye. Match each of the genotypes with the expected sex and eye color.

XX Female Red Xw X Female red XwY Male white XO Male red Xw XY Female red XwXwXw Metafemale red

Alleles A and a are located on a pair of metacentric chromosomes. Alleles B and b are located on a pair of acrocentric chromosomes. A cross is made between individuals having the genotypes Aa Bb and aa bb. Label the gametes of the aa bb parent with the chromosomes carrying the correct alleles. Which gametes can the Aa Bb parent generate?

a b - a b - a b - a b a b- A B

1. X-linked red-green color blindness in humans is a recessive condition. Which statement is true?

a. A color‑blind woman must have had a color‑blind father.

1. Which statements describe Y‑linked traits?

a. All male offspring of affected fathers will express the trait c. The trait is passed down to a son by his father.

1. Who discovered the basic principles of heredity?

a. Gregor Mendel

1. What happens during anaphase I of meiosis?

a. Homologous chromosomes separate, but sister chromatids remain joined at their centromeres.

1. What are the multiple forms of one gene called?

a. alleles

1. Which stage of mitosis involves sister chromatids separating and moving toward opposite poles?

a. anaphase

1. The products of mitosis normally

a. are genetically identical to the parent cell.

1. What is the constricted region of the chromosome where the kinetochore forms?

a. centromere

1. Which molecule holds sister chromatids together during mitosis and meiosis?

a. cohesin

1. What is a cross that occurs between two individuals that differ in two characteristics?

a. dihybrid cross

1. 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)(A) is dominant over albinism (𝑎)(a) . For this question, assume the phenotype is determined by a single gene with two alleles. If two people have normal pigmentation, what possible phenotypes may be observed in their offspring?

a. normal pigmentation or albinism

1. What early concept of heredity proposed that genetic information in the form of particles called gemmules travels from different parts of the body to reproductive organs?

a. pangenesis

1. Eukaryotic cells that contain more than two sets of genetic information are referred to as

a. polyploid.

1. If an Aa individual is crossed to an aa individual, what will be the phenotypic ratio in the offspring?

b. 1:1

1. The principle of independent assortment involves at least how many different gene pairs?

b. 2

1. A cross between an AABB individual and an aabb individual will produce what type of offspring?

b. All will be AaBb.

1. Of the following ideas postulated by Gregor Mendel, which one requires at least two genes to be demonstrated?

b. Genes assort independently in humans.

1. An X‑linked recessive gene causes red-green color blindness in humans. Suppose John and Cathy have normal color vision. After 10 years of marriage to John, Cathy has given birth to a color‑blind daughter and a color-blind son. John filed for divorce, claiming that he is not the father of at least one of the children. Which statement describes John's paternity claim?

b. He cannot be the father of Cathy's daughter.

1. What happens during metaphase I of meiosis?

b. Homologous chromosomes are randomly arranged in the middle of the cell.

1. What is the physical appearance or manifestation of a characteristic called in genetics?

c. phenotype

1. In fruit flies, long wings (W) are dominant over short wings (w), and red eyes (R) are dominant over orange eyes (r). Each individual possesses two alleles for each trait. If a fly that is homozygous dominant for both traits is crossed with a fly that is homozygous recessive for both traits, what is the predicted genotype of the offspring?

b. WwRr

1. Which characteristic would not be considered useful for a model genetic organism?

b. a long generation times

1. 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)(A) is dominant over albino characteristics (𝑎)(a) . For this question, assume the phenotype is determined by a single gene with two alleles. If both parents display the albino phenotype, what are all of the possible genotypes that may be observed in their offspring?

b. aa only

1. Mendel's principle of segregation can be explained by what process? a. fertilization b. meiosis c. none of these d. testcross e. mitosis

b. meiosis

1. The study of the chemical nature of the gene, and how genetic information is replicated and expressed, is part of what division of genetics?

b. molecular genetics

1. Sponges can produce sperm and eggs in a single organism. Which term describes the sex system of the organism?

b. monoecious

1. Suppose that life exists elsewhere in the universe. All life must contain some type of genetic information, but alien genomes might not consist of nucleic acids or have the same features as those found in the genomes of life on Earth. What might be the common features of all genomes, no matter where they exist?

b. the ability to store the entire set of information an organism needs for reproduction and development e. the ability to replicate the genetic information accurately for the next generation

1. A human male with the chromosome constitution of XXXYY would contain how many Barr bodies in his somatic cells?

c. 2

In pea plants, plant height is controlled by a single autosomal dominant gene. Tall plants (H) are dominant to short plants (h). In a cross of two tall heterozygous plants, which phenotype ratio is expected from the resulting offspring?

c. 3:1

1. Assume that a cell has six chromosomes while it is in the G1 stage of the cell cycle. How many chromosomes and how many DNA molecules will it have in the G2 stage?

c. 6 chromosomes and 12 DNA molecules

1. What did Mary Lyon propose about sex chromosomes in mammals?

c. One X chromosome in each female cell becomes inactivated, and the process of selection is random.

1. What characteristic makes prokaryotic cells different from eukaryotic cells?

c. Prokaryotic cells do not contain membrane‑bound organelles.

1. In which stage of the cell cycle does the cell duplicate its DNA?

c. S

1. Which of the statements is not a difference between mitosis and meiosis?

c. Sister chromatids separate during mitosis but not during meiosis.

1. What happens during anaphase II of meiosis?

c. Sister chromatids separate from each other and migrate to opposite ends of the cell.

1. When Mendel crossed a plant homozygous for round seeds to another plant homozygous for wrinkled seeds, he found that all the progeny had round seeds. How is this explained?

c. The allele for round seeds is dominant to the allele for wrinkled seeds.

An autotriploid (3𝑛)(3n) has three sets of homologous chromosomes in each cell instead of the usual pairs of homologous chromosomes present in diploid individuals (2𝑛).(2n). How would mitosis be different in an autotriploid?

c. There are more chromosomes that line up on the metaphase plate.

The Talmud, an ancient book of Jewish civil and religious laws, states that if a woman bears two sons who die of bleeding after circumcision (removal of the foreskin from the penis), any additional sons that she has should not be circumcised. The bleeding is most likely due to the X‑linked disorder hemophilia. Furthermore, the Talmud states that the sons of her sisters must not be circumcised, whereas the sons of her brothers should be. Is this religious law consistent with sound genetic principles?

c. Yes, the woman is a carrier and half of her sons will be affected. Her sisters may also be carriers, but her brothers' sons will get their X chromosomes from their mothers, who are unlikely to be carriers of the allele.

1. Which genetic condition is found at an unexpectedly high frequency among the Hopi Native Americans?

c. albinism

1. Meiosis results in genetic variation among its product cells. One source of this genetic variation is the random distribution of maternal and paternal chromosomes, and the other source of genetic variation is

c. crossing over occurring at prophase I.

1. Fruit flies are sexually reproducing insects with separate male and female individuals. Like most mammals, including humans, males have an X and a Y chromosome, and females have two X chromosomes. Select the term that describes the organization of the sexual organs in the fruit fly.

c. dioecious

1. In flowering plants, meiosis in the male portion of the flower produces a. four haploid sperm that are able to fertilize the egg produced by the female portion of the flower.

c. four microspores that will divide mitotically to form male gametophytes.

1. What is the complete set of genetic instructions for an organism?

c. its genome

1. What process involves the separation of chromosomes in the division of somatic, non-sex, cells?

c. mitosis

1. Cell division by mitosis is a mechanism of asexual cell replication. Some single‑celled organisms reproduce by cell division, and cell division enables multicellular organisms to grow and to repair damaged cells. Which is a product of cell division by mitosis?

c. two cells genetically identical to the original cell

1. How many ova, plural for ovum, can be produced from two primary oocytes through meiosis?

c.2

Suppose the tail length of two populations of jerboas is controlled by one gene. To determine the mode of inheritance, a homozygous short‑tailed female is crossed with a homozygous long‑tailed male. Then, siblings from the F1 are crossed, and the number of short‑ and long‑tailed animals are counted to determine the phenotype ratio. Match the phenotypic ratio anticipated in the offspring from a cross of two heterozygous individuals to the appropriate mode of inheritance for the short‑tail allele.

cross of heterozygotes, autosomal dominant: 1 Long : 3 Short autosomal recessive: 3Long : 1Short sex-linked dom.: males 1 long: 1 short; females all short sex-linked recessive . : 1 long: 1 short

1. What will be the genotypic ratio in the offspring of two Aa parents that are crossed with each other?

d. 1: 2: 1

1. A normal female Drosophila produces abnormal eggs that contain a complete diploid set of her chromosomes. She mates with a normal male Drosophila that produces normal sperm. What will the sex ratio of the progeny from this cross be?

d. 50% female, 50% intersex

1. Normally in humans, a mutant gene on the Y chromosome will be inherited in which way?

d. All of the sons of a parent with the mutant gene will receive it but none of the daughters will.

1. Which organism would not be considered a useful model genetic organism?

d. Bos taurus (the cow)

An autotriploid (3𝑛)(3n) has three sets of homologous chromosomes in each cell instead of the usual pairs of homologous chromosomes present in diploid individuals (2𝑛).(2n). How would meiosis be different in an autotriploid?

d. Gametes have a varying number of chromosomes from each set.

1. What happens during metaphase II of meiosis?

d. Sister chromatids are distributed in a single layer across the center of the cell.

1. If a plant has a genotype of Aa, we would assume which is true?

d. The A allele is dominant to the a allele.

1. What happens during telophase II of meiosis?

d. The nuclear membrane begins to form around haploid sets of chromosomes.

1. In which stage of meiosis does the separation of homologous chromosomes occur?

d. anaphase I

1. Which statement identifies what The Green Revolution relied upon genetic applications to accomplish? a. determine which species are most closely related to humans b. provide renewable energy sources c. cure certain genetic diseases in humans d. expand the world's food production e. synthesize new drugs

d. expand the world's food production

1. A fruit fly, Drosophila melanogaster, that has only one sex chromosome (XO) and two sets of autosomes would have which sexual phenotype?

d. male

1. An individual possesses two alleles at a locus and these two alleles separate when gametes are formed, one allele going into each gamete.

d. principle of segregation.

1. In what way have humans been applying the principles of heredity for millennia? a. the concept of the cell theory b. the proposal that genes are located on chromosomes c. the development of the germ-plasm theory d. the domestication of plants and animals e. the theory of evolution through natural selection

d. the domestication of plants and animals

1. Hemophilia is called "the royal disease" because many European royal families had members with the condition. Hemophilia is a recessive, X‑linked disorder. Queen Victoria was unaffected by hemophilia, but was a carrier of the hemophilia gene (XHXh). Suppose Queen Victoria's husband, Prince Albert, was affected with hemophilia (XhY). What is the percent probability that a son of Queen Victoria and Prince Albert would be unaffected by hemophilia? probability of unaffected son: What is the percent probability that a daughter or son of Queen Victoria and Prince Albert would be affected by hemophilia? probability of affected child: What is the percent probability Queen Victoria and Prince Albert would have two affected females? probability of two affected females:

probability of unaffected son: 50% probability of affected child: 50% probability of two affected females: 6.25 %

1. In pea plants, the allele for round seed shape, R, is completely dominant to the allele for wrinkled seed shape, r. Complete the Punnett square showing the genotypes possible among the offspring when two heterozygous individuals are crossed. Use the information from the Punnett square to answer the second question. In this cross between two heterozygous pea plants, what are the chances that an offspring with wrinkled seeds will be produced?

punnett square = R R - R r R r - r r 25%