Exam 3 lecture

Gametes are produced by _____.

A. mitosis
B. the cell cycle
C. meiosis
D. fertilization
E. asexual reproduction

Normal human gametes carry _____ chromosomes.

A. 23 pairs of
B. 5
C. 46
D. 23
E. 46 pairs of

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.

A. 30
B. 32
C. 16
D. 8
E. 64
Which of the following statements correctly describes the timing of DNA synthesis?
View Available Hint(s)for Part A

DNA is synthesized continuously throughout the cell cycle
DNA is synthesized in the S phase of interphase.
DNA is synthesized in G2 of interphase immediately preceding mitosis.
DNA is synthesized only during mitosis.Which of the following represents a chromosomally normal human female?

A. XXX
B. XXXX
C. XY
D. XX
E. YMeiosis II typically produces _____ cells, each of which is _____.

A. two ... haploid
B. four ... identical to the other
C. two... diploid
D. four ... diploid
E. four ... haploidIn an individual of genotype Aa, where are the A and a alleles physically located?

A. One allele is on one chromosome, and the other is in the same position (locus) on the homologous chromosome.
B. They are both on one chromosome.
C. One allele is on one chromosome, and the other allele is in a different position (locus) on the same chromosome.
D. One allele is on one chromosome, and the other allele is on a different (nonhomologous) chromosome.Imagine that long fins in zebrafish is a dominant trait. A breeder wants to set up a breeding program beginning with homozygous dominant long-finned fish. If she obtains a handful of the long-finned fish, how can she tell which, if any, of these are homozygous for the trait?

A. Cross the long-finned fish with short-finned fish; if the offspring are all long-finned, the long-finned parent is homozygous.
B. Cross the long-finned fish with short-finned fish; if four-fifths of the offspring are long-finned and one-fifth are short-finned, the long-finned parent is homozygous.
C. Cross the long-finned fish with short-finned fish; if three-fourths of the offspring are long-finned and one-fourth are short-finned, the long-finned parent is homozygous.
D. Cross the long-finned fish with short-finned fish; unless all of the offspring are short-finned, the long-finned parent is homozygous.You have one tree that produces big yellow apples and another tree that produces small red apples. When the two are crossed, you find that half the offspring trees produce big red apples and half produce big yellow apples. What are the genotypes of the parents? A = big apples; a = small apples; R = red apples; r = yellow apples.

A. AaRr and AaRr
B. Aarr and aaRr
C. AArr and aaRr
D. AARr and AArrSuppose we have a pea plant with purple flowers, determined by the dominant allele P. How might you determine whether the plant is homozygous (PP) or heterozygous (Pp)?

A. Perform a testcross: Cross the plant with a white one, which must be homozygous recessive (pp).
B. Examine the plant's chromosomes with a microscope.
C. Perform a testcross: Cross the plant with one with green seeds, which must be homozygous recessive (yy).
D. Cross the plant with a true-breeding purple plant.Two normal parents have three normal children: one son and two daughters. Their son and one of their daughters marry and also have normal children. Their second daughter, Mary, marries a man with a rare, recessive blood disorder. They have two children, and both children develop the blood disorder. What must be true of the genotypes of Mary's parents?

A. Her mother was heterozygous for the trait.
B. Her father was heterozygous for the trait.
C. Mary's parents were both homozygous for the trait.
D. Either one of her parents or both of her parents were heterozygous for the trait.Hypercholesterolemia is a disorder in which blood cholesterol levels are elevated. The H allele is incompletely dominant to the h allele, with hh homozygotes having extremely high levels of blood cholesterol. A husband and wife are both Hh heterozygotes. What is the chance that their first child will have normal levels of blood cholesterol?

A. 0
B. 1/4
C. 1/2
D. 3/4

Asexual and sexual reproduction differ in that sexual reproduction _____.
View Available Hint(s)for Part A

A. is the only way single-celled organisms can reproduce
B. is the only way multicellular organisms can reproduce
C. can produce great variation among the offspring
D. will produce offspring identical to the parents

Bacteria divide by:

A. mitosis
B. binary fission
C. meiosis
D. sexual reproduction

The first step of bacterial replication is _____.

A. pinching of the plasma membrane
B. DNA replication
C. attachment of the DNA to the plasma membrane
D. separation of daughter cells

What is different concerning the DNA in bacterial cells as opposed to eukaryotic cells?

A. the amount of DNA present
B. whether the DNA is housed in a nucleus or not
C. whether the DNA is linear or circular
D. all of the above are differences between prokaryotic and eukaryotic DNA

In bacterial cells, binary fission involves __________.
View Available Hint(s)for Part A

A. prophase, metaphase, anaphase, and telophase
B. distribution of a copy of the single parental chromosome to each daughter cell
C. formation of a cell plate
D. disintegration of the nuclear membrane

Chromatids are _____.
View Available Hint(s)for Part A

A. found only in aberrant chromosomes
B. identical copies of each other if they are part of the same chromosome
C. not present in the Y sex chromosome, but present in the X sex chromosome
D. held together by the centrioles

True or false. Mitosis takes place during M phase of the cell cycle, which is longer than interphase.
View Available Hint(s)for Part A

True
False

A certain species of animal has six pairs of chromosomes. How many DNA molecules are present in the nuclei of these animals during G2 phase?
View Available Hint(s)for Part B

24
12
48
6

Which of the following checkpoints does not occur late in G1?
View Available Hint(s)for Part C

A. A check that growth factors are present
B. A check that chromosome replication has been successfully completed
C. A check that nutrients are sufficient
D. A check that the cell is large enough for division

put these in order

interphase

prophase

anaphase

metaphase

telophase

Which of the following statements correctly describes the timing of DNA synthesis?
View Available Hint(s)for Part A

A. DNA is synthesized continuously throughout the cell cycle
B. DNA is synthesized in the S phase of interphase.
C. DNA is synthesized in G2 of interphase immediately preceding mitosis.
D. DNA is synthesized only during mitosis.

Part A
What must happen before a cell can begin mitosis?
View Available Hint(s)for Part A

A. The nucleus must divide in two.
B. A mitotic spindle must form.
C. The nuclear envelope must break up.
D. The chromosomes must be duplicated.
E. The sister chromatids must be separated.

The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
View Available Hint(s)for Part B

A. Interphase
B. Anaphase
C. Telophase
D. Metaphase
E. Prophase

The chromosomes line up in the center of the cell during which phase of mitosis?
View Available Hint(s)for Part C

A. Interphase
B. Anaphase
C. Metaphase
D. Prophase
E. Telophase

The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
View Available Hint(s)for Part D

A. Telophase
B. Anaphase
C. Interphase
D. Metaphase
E. Prophase

The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
View Available Hint(s)for Part E

A. Anaphase
B. Prophase
C. Metaphase
D. Interphase
E. Telophase

At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.

A. telophase
B. meiosis
C. cytokinesis
D. condensation
E. replication

The stage of mitosis during which the chromosomes move toward separate poles of the cell is _____.

A. anaphase
B. telophase
C. metaphase
D. cytokinesis

Nucleoli are present during _____.

A. interphase
B. metaphase
C. anaphase
D. prometaphase
E. prophase

Cytokinesis often, but not always, accompanies _____.

A. anaphase
B. metaphase
C. telophase
D. interphase
E. prometaphase

Chromosomes become visible during _____.

A. prometaphase
B. metaphase
C. anaphase
D. prophase
E. interphase

Centromeres divide and sister chromatids become full-fledged chromosomes during _____.

A. telophase
B. prometaphase
C. interphase
D. anaphase
E. metaphase

Spindle fibers attach to kinetochores during _____.

A. metaphase
B. anaphase
C. telophase
D. prometaphase
E. interphase

During prophase a homologous pair of chromosomes consists of _____.

A. two chromosomes and two chromatids
B. one chromosome and four chromatids
C. four chromosomes and two chromatids
D. two chromosomes and four chromatids
E. one chromosome and two chromatids

In the laboratory, cancer cells fail to show density-dependent inhibition of growth in cell culture. What is one explanation that could account for this?

A. Cancer cells are unable to attach to a surface and grow.
B. Cancer cells continuously secrete growth factors into the cell culture medium.
C. Cancer cells have inactive receptors for growth factors.
D. Cancer cells continue to die at a rate that is equal to their growth.

Which of the following represents a chromosomally normal human female?

A. XXX
B. X
C. XXY
D. XX

After fertilization, the resulting zygote begins to divide by __________.

A. mitosis
B. meiosis
C. binary fission
D. schizogony

Meiosis I produces _____ cells, each of which is _____.

A. two... diploid
B. two ... haploid
C. two... identical to the other
D. four ... diploid
E. four ... haploid

Meiosis II typically produces _____ cells, each of which is _____.

A. two ... haploid
B. four ... identical to the other
C. two... diploid
D. four ... diploid
E. four ... haploid

During _____ sister chromatids separate.

A. metaphase I
B. prophase I
C. interphase
D. prophase II
E. anaphase II

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.

A. telophase I
B. telophase
C. metaphase II
D. interphase
E. telophase II

Homologous chromosomes migrate to opposite poles during _____.

A. anaphase I
B. prophase II
C. metaphase I
D. telophase II and cytokinesis
E. metaphase II

During _____ chromosomes align single file along the equator of a haploid cell.

A. prophase I
B. metaphase II
C. telophase I and cytokinesis
D. metaphase I
E. anaphase I

At the end of _____ and cytokinesis there are four haploid cells.

A. prophase I
B. anaphase I
C. interphase
D. telophase II
E. prophase II

During _____ a spindle forms in a haploid cell.

A. prophase II
B. metaphase II
C. anaphase II
D. telophase I and cytokinesis
E. prophase I

Synapsis occurs during _____.

A. telophase I and cytogenesis
B. prophase I
C. anaphase II
D. prophase II
E. metaphase II

Meiosis starts with a single diploid cell and produces

A. four haploid cells.
B. four diploid cells.
C. eight haploid cells.
D. two diploid cells.
E. two haploid cells.

A cell preparing to undergo meiosis duplicates its chromosomes during

A. interphase.
B. anaphase I.
C. meiosis II.
D. metaphase I.
E. prophase I.

During prophase I of meiosis,

A. chromosome pairs are positioned in the middle of the cell.
B. homologous chromosomes stick together in pairs.
C. the homologous chromosomes separate and move towards opposite poles.
D. there are four haploid daughter cells.
E. there are two daughter cells, each with 23 chromosomes.

The correct order of events during meiosis is

A. metaphase I, prophase I, anaphase I, telophase I, cytokinesis, meiosis II.
B. prophase I, anaphase I, metaphase I, telophase I, meiosis II, cytokinesis.
C. metaphase I, prophase I, telophase I, anaphase I, cytokinesis, meiosis II.
D. prophase I, anaphase I, telophase I, metaphase I, meiosis II.
E. prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.

During meiosis, segments of nonsister chromatids can trade places. This recombination of maternal and paternal genetic material is a key feature of meiosis. During what phase of meiosis does recombination occur?

A. telophase I.
B. prophase I.
C. Metaphase I.
D. anaphase I.
E. meiosis II.

What is the typical result when a diploid cell undergoes meiosis?

A. four haploid cells
B. two haploid cells
C. two diploid cells
D. four diploid cells

Meiosis differs from mitosis in that _____ only occurs in meiosis.

A. cytokinesis
B. the formation of a spindle
C. the fragmentation of the nuclear envelope
D. crossing over

Mitosis occurs in _____; meiosis occurs in _____.

A. somatic or body cells ... germ cells in the testes or ovaries
B. germ cells in the testes or ovaries ... somatic or body cells
C. adult organisms ... zygotes and early embryos
D. sexually reproducing organisms ... asexually reproducing organisms

Looking through a light microscope at a cell undergoing division, you see that the condensed chromosomes have lined up along the midline of the cell. The homologous pairs are NOT joined in tetrads. Each chromosome takes its own place in line, independent of its homolog. You are witnessing _____.

A. interphase
B. metaphase of mitosis
C. metaphase of meiosis I
D. telophase of either mitosis or meiosis I

Fertilization joins _____ to produce a _____.

A. diploid zygotes ... gamete
B. haploid zygotes ... diploid gamete
C. homologous chromosomes ... tetrad
D. haploid gametes ... diploid zygote

Duplication of the chromosomes to produce sister chromatids _____.

A. occurs in meiosis but not in mitosis
B. occurs in mitosis but not in meiosis
C. occurs in both mitosis and meiosis
D. does not occur in either type of cell division

If it weren't for _____, chromosome number would double with every generation of sexual reproduction.

A. meiosis
B. mitosis
C. crossing over
D. fertilization

Variation occurs when chromosomes are shuffled in _____.

A. mutation
B. meiosis
C. mitosis
D. genetic drift

Which processes lead to most genetic variation in sexually reproducing organisms?
Select all that apply.

A. independent orientation of chromosomes in meiosis
B. cytokinesis
C. random fertilization
D. crossing over

Crossing over is _____.

A. the formation of tetrads
B. an independent assortment of chromosomes
C. the movement of genetic material from one chromosome to a nonhomologous chromosome
D. the exchange of homologous portions of nonsister chromatids

Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?

A. Down syndrome results in more serious symptoms than either trisomy 3 or trisomy 16.
B. Extra copies of the other somatic chromosomes are probably fatal.
C. Nondisjunction of chromosomes 3 and 16 probably occurs more frequently.
D. There are probably more genes on chromosome 21 than on either chromosomes 3 or 16.

You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication?

A. In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.
B. The chromosome number in trisomy would be normal; in a duplication, there would be one more chromosome.
C. The chromosome number in both cases would be normal, but in trisomy there would be three chromatids on one chromosome and in a duplication there would be two chromatids on one chromosome.
D. In both cases there would be an extra chromosome, but in trisomy there would be three chromatids on one chromosome and in... (The option is cut off)

A fragment of chromosome 21 reattaches to chromosome 21, but in the reverse direction. What is the name given to this change?

A. duplication
B. trisomy 21
C. deletion
D. inversion

In a monohybrid cross, F2 refers to __________.

A. the grandparents of the 1st generation
B. the original mating pair
C. the second filial generation, or the "grandchildren" of the original mating pair
D. the 1st filial generation

The cross-fertilization of two different, but true-breeding, varieties of pea plants will _____.

A. yield the P generation
B. produce an F2 generation
C. result in hybrid plants
D. be lethal

When applied to Mendel's experiments, the term true-breeding means a self-fertilization of two plants that produces __________.

A. offspring identical to the parent
B. offspring with only dominant traits
C. offspring with blended traits
D. offspring with only recessive traits

Imagine a particular character (such as flower color) that is determined by a single gene. If this gene is present in two forms, how can you tell which allele is dominant and which is recessive?

A. Perform a cross between two true-breeding individuals and observe the trait or traits expressed by the F2 individuals.
B. Perform a cross between two true-breeding individuals and observe the trait or traits expressed by the F1 individuals.
C. The trait that is most common in the population is the one determined by the dominant allele.
D. Cross one of the F1 individuals to either of the parents and observe the trait or traits expressed by their offspring.

An insect that has the genotype EeGGcc will have the same phenotype as an insect with the genotype __________.

A. EEGGCc
B. eeggcc
C. EEggcc
D. EEGGcc

A child with cystic fibrosis can be born to two parents who do not have the disease. This is because the disease _____.

A. is caused by a dominant allele
B. is caused by a recessive allele
C. occurs in individuals who received more than one allele from one or both parents
D. requires certain environmental conditions to be expressed

In an individual of genotype Aa, where are the A and a alleles physically located?

A. One allele is on one chromosome, and the other is in the same position (locus) on the homologous chromosome.
B. They are both on one chromosome.
C. One allele is on one chromosome, and the other allele is in a different position (locus) on the same chromosome.
D. One allele is on one chromosome, and the other allele is on a different (nonhomologous) chromosome.

What is an allele?

A. a variety of pea plant used by Mendel
B. an alternative version of a gene
C. a type of chromosome
D. the dominant form of a gene

Assume that in cattle a spotted coat is dominant to an even coat, short horns are dominant to long horns, and the traits for coat type and horn length assort independently. In a cross between cattle that are each heterozygous for both traits, what proportion of their offspring are expected to have long horns?

A. 1/16
B. 3/16
C. 1/4
D. 9/16

DdEe pea plants can produce _____ type(s) of gametes, but a ddee plant can produce _____ type(s) of gametes.

A. four ... one
B. two ... one
C. one ... two
D. four ... two

Pea flowers may be purple (P) or white (p). Pea seeds may be round (R) or wrinkled (r). What proportion of the offspring from the cross PpRr × PpRr are expected to have white flowers and wrinkled seeds?

A. 1/16
B. 3/16
C. 9/16
D. 12/16 or 3/4

Imagine that long fins in zebrafish is a dominant trait. A breeder wants to set up a breeding program beginning with homozygous dominant long-finned fish. If she obtains a handful of the long-finned fish, how can she tell which, if any, of these are homozygous for the trait?

A. Cross the long-finned fish with short-finned fish; if the offspring are all long-finned, the long-finned parent is homozygous.
B. Cross the long-finned fish with short-finned fish; if four-fifths of the offspring are long-finned and one-fifth are short-finned, the long-finned parent is homozygous.
C. Cross the long-finned fish with short-finned fish; if three-fourths of the offspring are long-finned and one-fourth are short-finned, the long-finned parent is homozygous.
D. Cross the long-finned fish with short-finned fish; unless all of the offspring are short-finned, the long-finned parent is homozygous.

You have one tree that produces big yellow apples and another tree that produces small red apples. When the two are crossed, you find that half the offspring trees produce big red apples and half produce big yellow apples. What are the genotypes of the parents? A = big apples; a = small apples; R = red apples; r = yellow apples.

A. AaRr and AaRr
B. Aarr and aaRr
C. AArr and aaRr
D. AARr and AArr

Suppose we have a pea plant with purple flowers, determined by the dominant allele P. How might you determine whether the plant is homozygous (PP) or heterozygous (Pp)?

A. Perform a testcross: Cross the plant with a white one, which must be homozygous recessive (pp).
B. Examine the plant's chromosomes with a microscope.
C. Perform a testcross: Cross the plant with one with green seeds, which must be homozygous recessive (yy).
D. Cross the plant with a true-breeding purple plant.

Three characteristics assort independently in one species of insect: Red eyes (R) are dominant to black eyes (r). Blue wings (B) are dominant to white wings (b). Green bodies (G) are dominant to yellow bodies (g). A cross is made between two heterozygous insects (RrBbGg). What is the probability that the offspring will be homozygous dominant for all three characteristics?

A. 1/64
B. 1/16
C. 1/8
D. 1/4

Two normal parents have three normal children: one son and two daughters. Their son and one of their daughters marry and also have normal children. Their second daughter, Mary, marries a man with a rare, recessive blood disorder. They have two children, and both children develop the blood disorder. What must be true of the genotypes of Mary's parents?

A. Her mother was heterozygous for the trait.
B. Her father was heterozygous for the trait.
C. Mary's parents were both homozygous for the trait.
D. Either one of her parents or both of her parents were heterozygous for the trait.

Part complete
Tay-Sachs disease runs in Rebecca's family. On a family pedigree, she saw a shaded circle. This represented _____.
View Available Hint(s)for Part A

A. a male with Tay-Sachs
B. a female carrier
C. a male carrier
D. a female with Tay-Sachs

Human genetic disorders __________.

A. are almost always life-threatening
B. are almost never observed in modern societies
C. are most often recessive
D. are most often dominant

Why are lethal dominant alleles so much more rare than lethal recessive alleles?

A. Less is known about lethal dominant disorders, so the rareness of these alleles is an artifact due to a lack of detection.
B. The types of mutations that create lethal dominant alleles are much less frequent than those that create lethal recessive alleles.
C. The lethality associated with lethal dominant alleles is much more severe than that associated with lethal recessive alleles.
D. Lethal dominant alleles are harmful whether they are carried in homozygous or heterozygous form, so there is always strong selection against these alleles.

Imagine you're counseling a couple who have undergone carrier screening for Tay-Sachs disease. The man is a carrier, and the woman does not carry the Tay-Sachs allele. How should you advise them?

A. They should be informed that if they have a child, there is a 50% chance that the child will have Tay-Sachs disease.
B. They should be informed that if they have a child, the child will not have Tay-Sachs disease but will have a 50% chance of being a carrier of the Tay-Sachs allele.
C. They should be informed that if they conceive a child, the child will have Tay-Sachs disease.
D. They should be informed that if they have a child, there is a 25% chance that the child will have Tay-Sachs disease.

Cystic fibrosis is inherited in an autosomal recessive pattern. Males who have cystic fibrosis are usually sterile. Furthermore, the disease is often lethal before the age of reproduction. Even though people with the disease rarely reproduce, cases continue to arise because __________.

A. new mutations continually introduce this harmful condition into the population
B. mosquitoes can transfer the disease from person to person
C. the harmful allele "hides" inside heterozygous individuals and one-fourth of the offspring of two heterozygotes should be afflicted
D. people continue to make inappropriate lifestyle choices

Many genetic disorders can be detected before birth. Procedures include _____, which is noninvasive, or _____, which allows the chromosomes of the fetus to be examined. Alternatively, maternal blood samples can be taken and tested for _____.

A. amniocentesis ... ultrasound imaging ... chorionic villus sampling
B. ultrasound imaging ... AFP ... amniocentesis
C. ultrasound imaging ... chorionic villus sampling ... AFP
D. amniocentesis ... AFP ... chorionic villus sampling

Hypercholesterolemia is a disorder in which blood cholesterol levels are elevated. The H allele is incompletely dominant to the h allele, with hh homozygotes having extremely high levels of blood cholesterol. A husband and wife are both Hh heterozygotes. What is the chance that their first child will have normal levels of blood cholesterol?

A. 0
B. 1/4
C. 1/2
D. 3/4

Flower color in snapdragons is an example of incomplete dominance. If a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with another pink-flowered plant, the expected progeny plants will be __________.

A. 50% pink and 50% red
B. 100% red
C. 25% red, 50% pink, and 25% white
D. 100% pink

There are over 100 alleles known for the gene associated with cystic fibrosis. With current technology, it is possible to determine exactly which allele or alleles is/are carried by a person. What is the maximum number of different alleles that any person can carry?

A. 2
B. 1
C. as many as there are alleles of the gene (~100 in this case)
D. 6

In lentils, the C gene has two different alleles. CSCS homozygotes have spotted seeds, CDCD homozygotes have dotted seeds, and CSCD heterozygotes have seeds with both spots and dots. This indicates that __________.

A. CD is completely dominant to CS
B. CS and CD are incompletely dominant
C. CS and CD are codominant
D. CS is completely dominant to CD

If one parent is blood type AB and the other is type O, what fraction of their offspring is expected to have blood type A?

A. 0
B. 0.5
C. 0.75
D. 1.0

Two parents of mixed ethnicity have twins, one of which is born with very light skin and one of which is born with very dark skin. This is because of __________.

A. exposure to sunlight
B. the pleiotropic effects of skin color genes
C. the inheritance of two linked skin color genes
D. the polygenic nature of skin color genes

The inheritance of height and weight can best be described as __________.

A. being caused by microorganisms
B. polygenic
C. the results of a bad lifestyle
D. Mendelian (dominant-recessive) inheritance

Our understanding of the role played by genes in many human characteristics is advancing rapidly in, for example, body size, performance on IQ tests, and personality traits. In this new genetic era, the role of the environment __________.

A. is important only in influencing personality traits
B. is to work with genes in complex and often unknown ways in the development of these traits
C. is always far more important than genes in the development of complex human traits
D. can largely be discounted in the development of complex human traits

Two identical twins are raised in different environments. They possess _____ genotypes and _____ phenotypes.

A. identical ... variable
B. contrasting ... identical
C. identical ... identical
D. identical ... dissimilar

Fraternal twins share _____ of the same genes, while identical twins share _____ of the same genes.

A. 25%; 75%
B. 100%; 50%
C. 50% on average; 100%
D. none; 50%

Linked genes are inherited together. This is because linked genes _____.

A. govern traits (such as hair texture and hair color) that are functionally related
B. are on the same chromosome
C. govern traits that have nothing to do with one another
D. have the same alleles residing on them

In a particular species of mammal, black hair (B) is dominant to green hair (b), and red eyes (R) are dominant to white eyes (r). When a BbRr individual is mated with a bbrr individual, offspring are produced in a ratio of 5 black hair and red eyes : 5 green hair and white eyes : 1 black hair and white eyes : 1 green hair and red eyes. Which of these explanations accounts for this ratio?

A. The expected results did not take genetic recombination into account.
B. Green-haired individuals have a higher prenatal mortality than black-haired individuals.
C. The genes for hair color and eye color are linked.
D. The genes for hair color and the genes for eye color are carried on different chromosomes.

If the two characteristics that Mendel looked at in his dihybrid cross of smooth yellow peas with wrinkled green peas had been controlled by genes that were located close together on the same chromosome, then the F2 generation __________.

A. would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment
B. would have contained only individuals that were heterozygous for both genes
C. would have contained four phenotypes in a 9:3:3:1 ratio
D. would have contained no individuals that were heterozygous for both genes

The existence of rare XY individuals who are phenotypically normal women was instrumental in learning about human sex determination. Maleness is determined by the SRY gene found on the Y chromosome. How is it possible to be an XY woman?

A. A portion of the Y chromosome containing SRY is duplicated.
B. The SRY locus changed position on the Y chromosome
C. The SRY locus of the Y chromosome is deleted.
D. The SRY locus of the Y chromosome has translocated (moved) to an autosome (a chromosome other than a sex chromosome).

The Y chromosomes of mammals contain genes that code for _____.

A. eye pigment, among many other characters
B. "maleness" and a few other characteristics
C. blood-clotting factor, among many other characters
D. both eye pigment and blood-clotting factor, among many other characters

A woman and her male partner have normal color vision. However, her father and her first son are colorblind. What is her genotype? Use C as the gene for colorblindness.

A. XCXc
B. XcXc
C. XCY
D. XCXC

A woman who is a carrier of hemophilia marries a man affected with hemophilia. What percentage of their sons and daughters is expected to have hemophilia?

A. 50% of sons and 0% of daughters
B. 50% of sons and 50% of daughters
C. 100% of sons and 50% of daughters
D. 0% of sons and 50% of daughters

Hemophilia appears rarely in females. This is because __________.

A. the female must possess the hemophilia allele on both X chromosomes
B. the female must possess the hemophilia allele on one X chromosome
C. it only affects females with two X chromosomes
D. it only affects males because they have only one X chromosome

We can better understand our ancestry by analyzing the __________ in males.

A. gene for colorblindness
B. Y chromosome
C. gene for SRY
D. X chromosome

Prokaryotic cells reproduce asexually by

A eukaryotic cell has ____ genes than a prokaryotic cell, and they are
grouped into multiple chromosomes in the ______.
A. more: nucleus
B. fewer: nucleus
C. more: cytoplasm
D. fewer: cytoplasm

Individual Chromosomes are visible under a

Which of the following statements most accurately describes the process of chromosome duplication and cell division in a eukaryotic cell?

A. Before cell division, chromosomes duplicate to form sister chromatids, which then separate to ensure each daughter cell receives a complete and identical set of chromosomes.
B. Chromosomes duplicate during cell division, and then each daughter cell receives a random assortment of the parent cell's genetic material.
C. Sister chromatids, which are non-identical DNA molecules, are produced after cell division to create a new set of chromosomes.
D. Cell division involves the duplication of centromeres, which then migrate to opposite sides of the cell to allow chromosomes to form.

Which of the following structures is responsible for connecting two identical DNA molecules (sister chromatids) after chromosome duplication?

A. Cytoplasm
B. Centromere
C. Nucleus
D. Daughter cell

A set of ______ within the cell controls the cell cycle

What cells deivide excessively to form masses called tumors

What do malignant tumors do ?

Meiosis, like mitosis, is preceded by chromosome duplication, but in
meiosis, the cell _____

An abnormal chromosome count is the result of

When can nondijunction occur during

Trisomy 21, the most common chromosome number abnormality,
results in a condition called

There are alternative versions of genes, called
_____, that account for variations in inherited traits