Biology topics 15 and 16

A new DNA strand elongates only in the 5' to 3' direction because A) DNA polymerase can only add nucleotides to the free 3' end. B)You Answered DNA polymerase begins adding nucleotides at the C)5' end of the template. D)the polarity of the DNA molecule prevents addition of nucleotides at the 3' end. E)replication must progress toward the replication fork.

A) DNA polymerase can only add nucleotides to the free 3' end.

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature? A)G with C B) G with U C)G with T D)G with A

A) G with C

A woman is red-green color-blind. What can we conclude, if anything, about her father? A) He is red-green color-blind. B)none of these answers is correct C)He has two Y chromosomes. D)There is a 50% probability that he has normal vision. E)We have too little information to tell.

A) He is red-green color-blind.

How do some scientists feel that telomerase might be used to slow the aging process? A) If telomerase activity was increased in our cells, the rate at which our chromosomes shorten as we age might be decreased. B)If telomerase activity was decreased in our cells, the rate at which our chromosomes shorten as we age might be decreased. C)If telomerase activity was increased in our cells, the rate at which our chromosomes lengthen as we age might be decreased. D)If telomerase activity was decreased in our cells, the rate at which our chromosomes lengthen as we age might be decreased.

A) If telomerase activity was increased in our cells, the rate at which our chromosomes shorten as we age might be decreased.

Which of the following statements describes the eukaryotic chromosome? A) It consists of a single linear molecule of double-stranded DNA plus proteins. B)The structure of the chromosome is determined by the nucleotide sequence of its DNA. C)It is composed of DNA alone. D)The number of genes on each chromosome is different in different cell types of an organism.

A) It consists of a single linear molecule of double-stranded DNA plus proteins.

Which of the following is the meaning of the chromosome theory of inheritance as expressed in the early 20th century? A) Mendelian genes are at specific loci on the chromosome and in turn segregate during meiosis. B)Individuals inherit particular chromosomes attached to genes. C)No more than a single pair of chromosomes can be found in a healthy normal cell. D) Homologous chromosomes give rise to some genes and crossover chromosomes to other genes. E)Natural selection acts on certain chromosome arrays rather than on genes.

A) Mendelian genes are at specific loci on the chromosome and in turn segregate during meiosis.

Why do some scientists feel that telomerase might be used to slow the aging process? A) Telomere extension in mice and worms has reversed some signs of aging. B)There is no real evidence; the idea that telomerase could be used to help reduce aging is based solely on theoretical arguments. C)Telomere extension in mice and worms allowed them to live to be approximately 100 years old D)Teleomere extension in humans has reversed some signs of aging.

A) Telomere extension in mice and worms has reversed some signs of aging.

Which of the following statements is true of linkage? A) The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them. B)The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%. C)Linked genes are found on different chromosomes. D)All of the traits that Mendel studied-seed color, pod shape, flower color, and others-are due to genes linked on the same chromosome. E)Crossing over occurs during prophase II of meiosis.

A) The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.

According to the "semi-conservative" model of DNA replication, A) after DNA replication occurs, each of the two double-stranded DNA molecules will consist of one "daughter" and one "parental" DNA strand B)each of the DNA strands in the double-stranded DNA molecules will consist of partly "parental" DNA and partly "daughter" DNA C) after DNA replication occurs, one of the two double-stranded DNA molecules will consist of two "daughter" DNA strands and the other will consist of two "parental" DNA strands D)after DNA replication occurs, one of the DNA strands in each double-stranded DNA molecule will consist of a mixture of "daughter" and "parental" DNA and the other DNA strand in each double-stranded DNA molecule will consist of all "daughter" DNA

A) after DNA replication occurs, each of the two double-stranded DNA molecules will consist of one "daughter" and one "parental" DNA strand

Which of the following would result in genetic variation by way of new combinations of alleles? A) all of these answers are correct B)random fertilization increasing the number of possible allele combinations in an individual C)independent alignment of homologous chromosomes during meiosis I D)the exchange of alleles between homologous chromosomes during meiosis I

A) all of these answers are correct

Inactivation of one of the two X chromosomes in females occurs early during embryo development. A random X chromosome is inactivated in each cell present during the period during which inactivation occurs. As a consequence A) females are a mosaic of two types of cell, those with the active X chromosome derived from the father and those with B)the active X chromosome derived from the mother. C)all of these answers are correct D) ½ the cells in a female embryo become unviable, and need to be replaced by mitosis of neighboring cells. E)different cells in a female embryo contain different X chromosomes

A) females are a mosaic of two types of cell, those with the active X chromosome derived from the father and those with

The recombination frequency between two gene loci is _____. A) greater as the distance between the two loci increases B)dependent on the sex of the parent C)dependent on whether dominant or recessive alleles are carried at the two loci D) greater as the distance between the two loci decreases E)equal to the size of the chromosome

A) greater as the distance between the two loci increases

If two genes are linked, _____. A) they are on the same chromosome B)they are on different chromosomes C)they code for the same protein D)they assort independently E)they are on sex chromosomes

A) they are on the same chromosome

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male? A) tortoiseshell females; black males B)orange females; black males C)tortoiseshell females; tortoiseshell males D)black females; orange males E)orange females; orange males

A) tortoiseshell females; black males

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes? A)100% B)50% C)0% D) 25% E)75%

A)100%

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below?5' TTCCGGA 3' A)5' TCCGGAA 3' B)5' UCCGGAA 3' C)5' AAGGCCT 3' D)5' AAGGCCT 3'

A)5' TCCGGAA 3'

A woman is red-green color-blind. What can we conclude, if anything, about her father? A)He is red-green color-blind. B)We have too little information to tell. C)none of these answers is correct D) There is a 50% probability that he has normal vision. E)He has two Y chromosomes.

A)He is red-green color-blind.

_____ is usually less severe than _____, and _____ species have been observed in plants, fish, amphibians, and even mammals. A)Polyploidy ... aneuploidy ... polyploid B)Nondisjunction ... disjunction ... nondisjunctional C)Monosomy ... trisomy ... monosomic D) Aneuploidy ... polyploidy ... aneuploid E)Trisomy ... monosomy ... trisomic

A)Polyploidy ... aneuploidy ... polyploid

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature? A)T with A B)T with U C)T with C D)T with G

A)T with A

Which of the following best describes the function of the XIST gene in X chromosome inactivation? A)The XIST gene on the X chromosome to be inactivated is expressed to produce multiple RNA transcripts that bind to that chromosome and effectively cover it up, thereby generating a Barr body. B)The XIST gene codes for an enzyme that methylates DNA on the X chromosome being inactivated. C)Together with other proteins, the product of the XIST gene binds to histones and induces supercoiling of the DNA in one of the X chromosomes, thus inactivating it. D)Protein encoded by the XIST gene coats one of the X chromosomes, causing that X chromosome to form an inactive Barr body.

A)The XIST gene on the X chromosome to be inactivated is expressed to produce multiple RNA transcripts that bind to that chromosome and effectively cover it up, thereby generating a Barr body.

In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine) for several minutes and then switched to nonradioactive medium. It is then viewed by electron microscopy and autoradiography. The figure shown below represents the results.The grains in the figure represent radioactive material within the replicating eye.Which of the following is the most likely interpretation? A)There are two replication forks going in opposite directions. B)Replication proceeds in one direction only. C)Thymidine is only being added where the DNA strands are furthest apart. D)Thymidine is only added at the very beginning of replication.

A)There are two replication forks going in opposite directions.

Which of the following would you expect of a eukaryote lacking telomerase? A)a reduction in chromosome length in gametes B)inability to repair thymine dimers C) a high probability of somatic cells becoming cancerous D)increased rates of DNA mutations

A)a reduction in chromosome length in gametes

Which of the following statements regarding DNA polymerases is TRUE? A)all of these statements are true B)DNA polymerases can NOT initiate synthesis of a new deoxyribonucleotide chain C)DNA polymerases can add nucleotides to the 3' end of an RNA molecule D)DNA polymerases can only add nucleotides to the 3' end of a nucleotide chain

A)all of these statements are true

The formation of hydrogen bonds between complementary nucleotides is known as A) base pairing B)complementation C)homologous joining D)DNA binding

A)base pairing

A "sex-linked" gene is a A)gene found on either the X or Y chromosomes B) gene that determines whether an individual is biologically male or female C)gene that determines how attractive an individual is to the other sex D)gene that determines an individual's sex drive

A)gene found on either the X or Y chromosome

The two strands of a double-stranded DNA molecule are held together by A)hydrogen bonds between complementary nitrogenous bases B)hydrogen bonds between sugar groups C)ionic bonds between phosphate groups and nitrogenous bases D)hydrogen bonds between phosphate groups

A)hydrogen bonds between complementary nitrogenous bases

"Linked genes" are A)located near each other on the same chromosome and thus tend to be inherited together B)genes involved in holding together homologous pairs of chromosomes during metaphase I of meiosis I C)involved in similar metabolic processes D)genes involved in holding together sister chromatids during meiosis I

A)located near each other on the same chromosome and thus tend to be inherited together

DNA replication begins are special sites on the parental DNA molecule known as A)origins of replication B)DNA polymerase binding sites C)primase binding sites D)Okazaki regions

A)origins of replication

Telomeres are A)the ends of linear chromosomes B)pores in the nuclear membrane that allow for passage of materials into and out of the nucleus C)part of the extracellular matrix D) attachment sites for the mitotic spindle apparatus

A)the ends of linear chromosomes

An Okazaki fragment has which of the following arrangements? A)5' DNA to 3' B) 5' RNA nucleotides, DNA nucleotides 3' C)DNA polymerase I, DNA polymerase III D)3' RNA nucleotides, DNA nucleotides 5'

B) 5' RNA nucleotides, DNA nucleotides 3'

In werewolves (hypothetically), pointy ears (P) are dominant over round ears (p). The gene is on the X chromosome. (Sex determination in werewolves is the same as for "other" humans.) A certain female werewolf has pointy ears even though her father had round ears. What percentage of her sons will have round ears if she mates with a werewolf with round ears? A)100% B) 50% C)25% D)75% E)0%

B) 50%

The chromosome theory of inheritance states that _____. A)genes occupy specific positions on chromosomes B) All these answers are correct. C)chromosomes assort independently during meiosis D)homologous chromosomes segregate from each other during meiosis

B) All these answers are correct.

Recombination between linked genes comes about for what reason? A)When genes are linked they always "travel" together at anaphase. B) Crossovers between these genes result in chromosomal exchange. C)Independent assortment sometimes fails because Mendel had not calculated appropriately. D)Mutation on one homolog is different from that on the other homolog.

B) Crossovers between these genes result in chromosomal exchange.

X-linked genes differ from Y-linked genes in which of the following ways? A) Sons and daughters can inherit alleles of X-linked genes from fathers proportionally but only sons inherit alleles of Y-linked genes from their fathers. B) Sons and daughters have equal probabilities in inheriting a recessive allele of an X-linked gene from their mother, but only sons can inherit rare Y-linked genetic disorders from their father. C)Though most X-linked genes determine sex, Y-linked genes control for characters unrelated to sex. D)Although the X and Y chromosomes carry genes that determine sexual characteristics, there are not corresponding regions of homology for genes located on each chromosome. E)Only X-linked genes are technically sex-linked because Y-linked genes affect characteristics unrelated to sex.

B) Sons and daughters have equal probabilities in inheriting a recessive allele of an X-linked gene from their mother, but only sons can inherit rare Y-linked genetic disorders from their father.

Which of the following statements is true of linkage? A)Crossing over occurs during prophase II of meiosis. B) The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them. C)The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%. D)All of the traits that Mendel studied-seed color, pod shape, flower color, and others-are due to genes linked on the same chromosome. E)Linked genes are found on different chromosomes.

B) The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.

A red-eyed female fly was crossed with a white-eyed male fly. All the F1 offspring had red eyes. Two of these red-eyed F1 generation flies were crossed to each other. The F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result? A)The gene involved is on an autosome, but only in males. B) The gene involved is on the X chromosome. C)Other male-specific factors influence eye color in flies. D) Other female-specific factors influence eye color in flies. E)The gene involved is on the Y chromosome.

B) The gene involved is on the X chromosome.

When a person has Down syndrome, he or she has an extra chromosome 21. Therefore, Down syndrome is a kind of _____ and results from _____. A)none of these answers is correct B) aneuploidy ... nondisjunction of chromosome 21 during meiosis I C)replication error ... an extra cycle of DNA synthesis during the S phase D)polyploidy ... occurrence of meiosis without cytokinesis E)genomic imprint ... excessive methylation of either the paternal or maternal chromosome 21

B) aneuploidy ... nondisjunction of chromosome 21 during meiosis I

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent A)Okazaki fragments and RNA primers. B) leading strands and Okazaki fragments. C) leading strands and RNA primers. D)lagging strands and Okazaki fragments.

B) leading strands and Okazaki fragments.

Which of the following represents the order of increasingly higher levels of organization of chromatin? A)looped domain, 30-nm chromatin fiber, nucleosome B) nucleosome, 30-nm chromatin fiber, looped domain C) 30-nm chromatin fiber, nucleosome, looped domain D)nucleosome, looped domain, 30-nm chromatin fiber

B) nucleosome, 30-nm chromatin fiber, looped domain

What is the probability that a male will inherit an X-linked recessive allele from his father? A)50% B) 0% C)25% D)100% E)75%

B)%

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes? A) 0% B)100% C)75% D)25% E)50%

B)100%

Hemophilia is a sex-linked disorder. The daughter of a father with hemophilia and a carrier mother has a _____ probability of having hemophilia. A)100% B) 50% C)33% D)25% E)0%

B)50%

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? A)The origins of replication occur only at the 5' end. B)DNA polymerase can join new nucleotides only to the 3' end of a growing strand. C) DNA ligase works only in the 3' → 5' direction. D)Polymerase can work on only one strand at a time.

B)DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

X-linked genes differ from Y-linked genes in which of the following ways? A)Only X-linked genes are technically sex-linked because Y-linked genes affect characteristics unrelated to sex. B)Sons and daughters have equal probabilities in inheriting a recessive allele of an X-linked gene from their mother, but only sons can inherit rare Y-linked genetic disorders from their father. C)Though most X-linked genes determine sex, Y-linked genes control for characters unrelated to sex. D)Although the X and Y chromosomes carry genes that determine sexual characteristics, there are not corresponding regions of homology for genes located on each chromosome. E)Sons and daughters can inherit alleles of X-linked genes from fathers proportionally but only sons inherit alleles of Y-linked genes from their fathers.

B)Sons and daughters have equal probabilities in inheriting a recessive allele of an X-linked gene from their mother, but only sons can inherit rare Y-linked genetic disorders from their father.

Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons? A)The gene order on the chromosomes is slightly different in every individual. B)The frequency of crossing over varies along the length of the chromosome. C)The relationship between recombination frequency and map units is different in every individual. D)Physical distances between genes change during the course of the cell cycle.

B)The frequency of crossing over varies along the length of the chromosome.

A "Barr body" is A)an inactive Y chromosome B)an inactive X chromosome C)an active Y chromosome D)an active X chromosome

B)an inactive x chromosome

The covalent linkages joining together nucleotides in a DNA molecule are known as A)You Answered nucleotide linkages B)phosphodiester linkages C)glycosidic bonds D)peptide bonds

B)phosphodiester linkages

Which of the following will happen to your chromosomes as you become older? A)All of these answers are correct. B)Your chromosomes will become shorter. C)The frequency of mutations will become smaller as DNA repair enzymes do their job. D)Your DNA will accumulate segments of RNA that are left over from the work of primase.

B)your chromosomes will become shorter

What would be the sequence of the DNA molecule made by replication of the DNA molecule shown below?5' GCGAATA 3' A)5' CGCTTAT 3' B) 5' UAUUCGC 3' C) 5' TATTCGC 3' D)5' CGCTTAT 3'

C) 5' TATTCGC 3'

Four genes (A, B, C, and D) are on the same chromosome. The recombination frequencies are as follows: A-B: 19%; B-C: 14%; A-C: 5%; B-D: 2%; A-D: 21%; C-D: 16%. Based on this information, which sequence of genes is correct? A)ADBC B)ABDC C) ACBD D)ABCD

C) ACBD

Queen Victoria was a carrier of a recessive sex-linked allele for hemophilia. Which of the following possibilities could explain the presence of the hemophilia allele in her genotype? A)none of these answers is correct B) Either her mother was a carrier or her father had a dominant allele C) Either her mother was a carrier or her father had hemophilia. D)Either her mother was homozygous dominant or her father had hemophilia. E)Both her mother and her father had hemophilia.

C) Either her mother was a carrier or her father had hemophilia.

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)Nondisjunction of chromosomes 3 and 16 probably occurs much less frequently. B)Down syndrome is not more common, just more serious. C) Extra copies of the other chromosomes are probably fatal to the developing embryo. D) There are probably more genes on chromosome 21 than on the others. E)Chromosome 21 is a sex chromosome, and 3 and 16 are not.

C) Extra copies of the other chromosomes are probably fatal to the developing embryo.

Which of the following shows the correct base pairing of deoxyribonucleotides that occurs in nature? A)G with U B)G with T C)G with C D)G with A

C) G with C

Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons? A)Physical distances between genes change during the course of the cell cycle. B)The gene order on the chromosomes is slightly different in every individual. C) The frequency of crossing over varies along the length of the chromosome. D)The relationship between recombination frequency and map units is different in every individual.

C) The frequency of crossing over varies along the length of the chromosome.

Cells that have a number of chromosomes different from the normal number for their species are known as _____. A)trisomy B)nanoploid C) aneuploid D)diploid E) polyploid

C) aneuploid

In Klinefelter syndrome, individuals are phenotypically male, but they have reduced sperm production and may have some breast development in adolescence. The cells of Klinefelter individuals have two X chromosomes and one Y (they are XXY instead of XY). This occurs because of what meiotic error? A)duplication B) polyploidy C) aneuploidy D)translocation D)monosomy

C) aneuploidy

A linkage map _____. A)predicts the probability that you will have a male or female child B)can be constructed only for sex chromosome C) orders genes on a chromosome based on recombination frequencies D)shows the ordering and exact spacing of genes on a chromosome E)orders genes on a chromosome based on their location with respect to a stained band

C) orders genes on a chromosome based on recombination frequencies

In an X-linked, or sex-linked, trait, it is the contribution of _____ that determines whether a son will display the trait. A)the paternal grandmother B)the father C) the mother D)none of these answers is correct E)the paternal grandfather

C) the mother

A genetic defect in humans results in the absence of sweat glands in the skin. Some men have this defect all over their bodies, but in women it is usually expressed in a peculiar way: A woman with this defect typically has small patches of skin with sweat glands and other patches without sweat glands. In women, the pattern of sweat-gland distribution can best be explained by _____. A)a homeobox B) RNA splicing C) X chromosome inactivation D)a mutation E)an operon

C) x chromosome inactivation

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base? A)All four bases of the DNA would be radioactive. B)One of the daughter cells, but not the other, would have radioactive DNA. C)DNA in both daughter cells would be radioactive. D)Neither of the two daughter cells would be radioactive.

C)DNA in both daughter cells would be radioactive.

In humans, which chromosome combinations normally determine whether an individual is biologically female or male? A)XX individuals are biologically female, YY individuals are biologically male B)Diploid individuals are biologically female, haploid individuals are biologically male C)XX individuals are biologically female, XY individuals are biologically male D)XY individuals are biologically female, XX individuals are biologically male

C)XX individuals are biologically female, XY individuals are biologically male

According to the "semi-conservative" model of DNA replication, after a double-stranded DNA molecule is replicated A)each DNA strand of one of the two resulting double-stranded DNA molecules will consist partly of "daughter" DNA and partly of "parental" DNA and each DNA strand of the other double-stranded DNA molecule will consist solely of "daughter" DNA B)each DNA strand of each of the two resulting double-stranded DNA molecules will consist partly of "daughter" DNA and partly of "parental" DNA C)each of the two resulting double-stranded DNA molecules will consist of one "daughter" and one "parental" DNA strand D)one of the two resulting double-stranded DNA molecules will consist of two "daughter" DNA strands and the other double-stranded DNA molecule will consist of two "parental" DNA strands

C)each of the two resulting double-stranded DNA molecules will consist of one "daughter" and one "parental" DNA strand

Histones are A)part of telomeres B)part of centromeres C) part of nucleosomes D)part of DNA replication origins

C)part of nucleosomes

How do the nucleotides used to make RNA molecules differ from those used to make DNA molecules? A)the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and uracil instead of adenine as one of their nitrogenous bases B)the nucleotides used to make RNA molecules have deoxyribose instead of ribose as their sugar and uracil instead of thymine as one of their nitrogenous bases C)the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and uracil instead of thymine as one of their nitrogenous bases D)the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and two phosphate groups instead of three

C)the nucleotides used to make RNA molecules have ribose instead of deoxyribose as their sugar and uracil instead of thymine as one of their nitrogenous bases

A woman is a carrier for red-green color blindness, a sex-linked trait. Her husband is normal (not color-blind) for this trait. What are the chances that their newborn daughter will be red-green color-blind? A)100% B) 50% C)25% D) 0% E)75%

D) 0%

Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila in which of these ways? A)The overall number of genes in Drosophila is a multiple of four. B)Drosophila genes have, on average, four different alleles. C)There are four major functional classes of genes in Drosophila. D) Drosophila genes cluster into four distinct groups of linked genes. E)The entire Drosophila genome has approximately 400 map units.

D) Drosophila genes cluster into four distinct groups of linked genes.

Duchenne muscular dystrophy is caused by a sex-linked recessive allele. Its victims are almost invariably boys, who usually die before the age of 20. Why is this disorder almost never seen in girls? A)Sex-linked traits are never seen in girls. B)The allele is carried on the Y chromosome. C)Nondisjunction occurs in males but not in females. D) To express an X-linked recessive allele, a female must have two copies of the allele. E)A sex-linked allele cannot be passed from mother to daughter.

D) To express an X-linked recessive allele, a female must have two copies of the allele.

In a nucleosome, the DNA is wrapped around A) ribosomes. B)satellite DNA. C)polymerase molecules. D) histones.

D) histones.

"Linked genes" are A)involved in similar metabolic processes B)genes involved in holding together homologous pairs of chromosomes during metaphase I of meiosis I C) genes involved in holding together sister chromatids during meiosis I D) located near each other on the same chromosome and thus tend to be inherited together

D) located near each other on the same chromosome and thus tend to be inherited together

Males are more often affected by sex-linked traits than females because A)male hormones such as testosterone often alter the effects of mutations on the X chromosome. B)X chromosomes in males generally have more mutations than X chromosomes in females. C)mutations on the Y chromosome often worsen the effects of X-linked mutations. D) males only have one copy of the X chromosome. E)female hormones such as estrogen often compensate for the effects of mutations on the X chromosome.

D) males only have one copy of the X chromosome.

Because the frequency of crossing over is not uniform along the length of a chromosome, _____. A)pairs of homologous chromosomes contain small but significant differences in gene order B)recombination frequency cannot be used to determine the number of centiMorgans separating two genes C)the centiMorgan is an unreliable unit of measurement, and is rarely used today D) map units do not necessarily correlate to physical distances along the chromosome E)the recombination frequency between two genes cannot be used to calculate the number of map units separating them

D) map units do not necessarily correlate to physical distances along the chromosome

Women (and all female mammals) have one active X chromosome per cell instead of two. What causes this? A)activation of the XIST gene on the Y chromosome, which then inactivates one of the X chromosomes B)the removal of methyl (CH3) groups from the X chromosome that will remain active C) inactivation of the XIST gene on the X chromosome derived from the male parent D) modification of the XIST gene so that it is active only on one X chromosome, which then becomes inactive E)crossover between the XIST gene on one X chromosome and a related gene on an autosome

D) modification of the XIST gene so that it is active only on one X chromosome, which then becomes inactive

"X inactivation" refers to A)the degradation of the X chromosome by the Y chromosome in genetic males B)the inactivation of most of the genes on the X chromosome of genetic males C) the inactivation of most of the genes on both X chromosomes in genetic females D) the inactivation of most of the genes on one X chromosome in genetic females

D) the inactivation of most of the genes on one X chromosome in genetic females

Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine? A)24 B)31 C)38 D)12

D)12

In humans, male-pattern baldness is controlled by an autosomal gene (= a gene that is found on a chromosome other than an X or Y chromosome) that occurs in two allelic forms. Allele Hn determines nonbaldness, and allele Hb determines pattern baldness. In males, because of the presence of testosterone, allele Hb is dominant over Hn. If a man and woman both with genotype HnHb have a son, what is the chance that he will eventually be bald? A)0% B)33% C)50% D)75% E)25%

D)75%

Why do some scientists feel that telomerase might be used to slow the aging process? A)Teleomere extension in humans has reversed some signs of aging. B)Telomere extension in mice and worms allowed them to live to be approximately 100 years old C)There is no real evidence; the idea that telomerase could be used to help reduce aging is based solely on theoretical arguments. D)Telomere extension in mice and worms has reversed some signs of aging.

D)Telomere extension in mice and worms has reversed some signs of aging.

The order in which chromatin packing occurs is as follows: A)The DNA wraps around histones, forming nucleosomes; the chromatin forms loops by attaching to scaffold proteins; the histones within each nucleosome interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber B)The chromatin forms loops by attaching to scaffold proteins; the histones within nucleosomes interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber; the DNA wraps around histones, forming nucleosomes C)The histones within nucleosomes interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber; the chromatin forms loops by attaching to scaffold proteins, forming a 300-nm fiber; the DNA wraps around histones, forming nucleosomes D)The DNA wraps around histones, forming nucleosomes; the histones within each nucleosome interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber; the chromatin forms loops by attaching to scaffold proteins, forming a 300-nm fiber

D)The DNA wraps around histones, forming nucleosomes; the histones within each nucleosome interact with adjacent nucleosomes and with the DNA between nucleosomes to form a 30-nm fiber; the chromatin forms loops by attaching to scaffold proteins, forming a 300-nm fiber

Which of the following shows the correct base pairing of ribonucleotides that occurs in nature? A)U with C B)U with T C)U with G D)U with A

D)U with A

Which of the following statements regarding primases is TRUE? A)Primases add nucleotides to the 3' end of a nucleotide or nucleotide chain B)Primases catalyze the formation of an RNA molecule C)Primases can initiate synthesis of a new nucleotide chain D)all of these statements are true

D)all of these statements are true

Which of the following enzymes covalently connects segments of DNA? A)DNA polymerase I B)DNA polymerase III C)primase D)ligase

D)ligase

During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as _____. A)meiotic failure B)cellular sterility C)gametic infertility D)nondisjunction E)sticky chiasmata

D)nondisjunction

The leading and the lagging strands differ in that A)the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together. B)the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end. C)the leading strand is synthesized at twice the rate of the lagging strand. D)the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

D)the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

If a mother is heterozygous for a recessive sex-linked trait and her husband has the dominant allele, which one of the following is true about the probabilities for their children? A)None of their sons will have the recessive trait. B)All of their sons will have the recessive trait. C)No answer text provided. D)All of their daughters will be heterozygous. E) Half of their sons will have the recessive trait.

E) Half of their sons will have the recessive trait

What does a frequency of recombination of 50% indicate? A)The genes are located on sex chromosomes. B)Abnormal meiosis has occurred. C)Independent assortment is hindered D) All of the offspring have combinations of traits that match one of the two parents. E) The two genes are likely to be located on different chromosomes.

E) The two genes are likely to be located on different chromosomes.

What is the function of DNA polymerase III? A)to unwind the DNA helix during replication B)to rejoin the two DNA strands (one new and one old) after replication C)to seal together the broken ends of DNA strands D)This job is done by DNA ligase. E) to add nucleotides to the 3' end of a growing DNA strand

E) to add nucleotides to the 3' end of a growing DNA strand

The centimorgan (cM) is a unit named in honor of Thomas Hunt Morgan. To what is it equal? A)the distance between a pair of homologous chromosomes B)the recombination frequency between two genes assorting independently C)1 nanometer of distance between two genes D) the physical distance between two linked genes E)1% frequency of recombination between two genes

E)1% frequency of recombination between two genes

How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced? A) The two genes are linked but on different chromosomes. B)The testcross was improperly performed. C)Recombination did not occur in the cell during meiosis. D)Both of the characters are controlled by more than one gene. E)The two genes are closely linked on the same chromosome.

E)The two genes are closely linked on the same chromosome.