Exam #3 - Reading Quiz and HW Questions

What is a purine?

-Adenine or guanine -A base with two rings

A problem known as the end-replication problem (telomere problem) exists in eukaryotic chromosomes wherein the chromosomes shorten with each round of DNA replication. Explain why the end-replication problem exists in eukaryotic chromosomes.

-DNA polymerase requires a primer for DNA synthesis. -DNA polymerase synthesizes DNA from the phosphate end to the hydroxyl end.

Identify the key structural features of a DNA molecule.

-DNA strands are antiparallel and include a 5' end and a 3' end. -The backbone of DNA is made of a sugar and a phosphate molecule. -DNA bases are always paired using Watson-Crick base pairing.

What does the term antiparallel mean?

-The 5' end of one strand is opposite the 3' end of the second strand. -The strands run in opposite directions.

In 1953, the scientists James Watson and Francis Crick published their landmark findings on the structure of DNA. Watson and Crick deduced the structure of DNA by unifying evidence that they collected from several scientists who were also seeking to answer this important question. Identify the pieces of evidence describing the features of DNA that Watson and Crick used to determine the structure of DNA.

-The diameter of the DNA double helix is 2 nanometers, with each purine-pyrimidine base pair spanning an equivalent distance between the two chains. -A purine base forms hydrogen bonds to pair with a pyrimidine base located on the opposite DNA strand. Specifically, A pairs with T, and C pairs with G. -The sugar-phosphate backbones of each DNA helix run antiparallel to one another. -DNA forms a right-handed double helical structure with two polynucleotide chains coiled around a central axis.

What conclusions can you draw from this data? Organism--A%--G%--T%--C% Human--31--20--30--19 Chicken--28--21--29--22 Yeast--32--18--33--17 E. coli--26--25--24--25

-The proportion of A is roughly equal to the proportion of T. -The proportion of purines is roughly equal to the proportion of pyrimidines. -The proportion of C is roughly equal to the proportion of G.

Eukaryotic DNA consist of:

-highly repetitive DNA sequences. -unique sequences of DNA -moderately repetitive DNA sequences

James Watson and Francis Crick used the X-ray diffraction image taken by Rosalind Franklin shown below to deduce structural properties of B-form DNA. What findings did Watson and Crick make from this image?

-includes 10 base pairs per repeat -has a consistent diameter -shaped like a helix

In the fruit fly, Drosophila melanogaster, a known deletion on the X chromosome removes both a gene involved in the fly\'s development and the gene for eye color. The deletion is lethal when homozygous or hemizygous. Flies that are heterozygous for the mutation are viable, but have indentations at the wing margin. Therefore, the deletion is named the Notch mutation. The allele for wild type eyes is dominant over the allele for white eyes. Predict the phenotypic ratio of the offspring from a cross between a white-eyed notched female and a wild type male.

1 wild type female : 1 notched female : 1 white-eyed male

Complete the following sentences about DNA packaging. 1.) The less condensed form of chromatin is ____. 2.) The inactive form of chromatin is _____. 3.) A core composed of eight _____ proteins interacts with DNA through hydrogen bonding and ionic bonds. 4.) If DNA structure is described as "beads-on-a-string," a "bead" is a _____. 5.) The more darkly-staining form of chromatin is ______. 6.) If DNA structure is described as "beads-on-a-string," a "string" is a _____. 7.) A _____ is a DNA-protein complex.

1.) euchromatin 2.) heterochromatin 3.) histone 4.) nucleosome 5.) heterochromatin 6.) DNA molecule 7.) nucleosome

Gunter Korge examined several proteins that are secreted from the salivary glands of Drosophila melanogaster during larval development. One protein, called protein fraction four, was encoded by a gene found by deletion mapping to be located on the X chromosome at position 3C. (G. Korge. 1975. Proceedings of the National Academy of Sciences of the United States of America 72:45504554). Korge observed that, about five hours before the first synthesis of protein fraction four, an expanded and puffed-out region formed on the X chromosome at position 3C. This chromosome puff disappeared before the end of the third larval instar stage, when the synthesis of protein fraction four ceased. He observed that there was no puff at position 3C in a special strain of flies that lacked secretion of protein fraction four. 1.) What is the chromosome puff at position 3C? 2.) Why does the disappearance of the puff at position 3C roughly coincide with lack of the secretion of protein fraction 4?

1.) A region of active transcription 2.) The disappearance of the puff at region 3C indicates a lack of transcription from the region with gene for protein fraction 4.

List the steps of eukaryotic DNA replication in order, from when a germ cell enters gap 1 (G1) phase to the cell cycle termination.

1.) Cell enters gap 1. 2.) Prereplication complex forms at one of many origins of replication. 3.) The initiation complex creates an active replication fork as helicase unwinds DNA. 4.) RNA primers are added to provide a 3' end for elongation. 5.) DNA polymerase synthesizes both the leading and lagging strands from 5' to 3'. 6.) RNA is replaced by DNA and lagging strands are joined. 7.) Active telomerase can extend the lost telomere region. 8.) Cell cycle termination.

Multiple proteins are involved in DNA replication, and each protein has a unique role. Use the image below to visualize some of these proteins. Note that DNA topoisomerase and DNA ligase are not shown. Match each protein to its role in DNA replication. 1.) relaxes the supercoiled DNA 2.) unwinds the DNA double helix 3.) prevents the reannealing of DNA strands 4.) synthesizes new DNA 5.) connects the separated DNA segments

1.) DNA topoisomerase 2.) helicase 3.) SSB protein 4.) DNA polymerase III 5.) DNA ligase

Match the researchers with the discoveries listed. 1.) Took X-ray diffraction pictures used in constructing the structure of DNA 2.) Determined that DNA contains nitrogenous bases 3.) Identified DNA as the genetic material in bacteriophage 4.) Discovered regularity in the ratios of different bases in DNA 5.) Determined that DNA is responsible for transformation in bacteria 6.) Worked out the helical structure of DNA by building models 7.) Discovered that DNA consists of repeating nucleotides 8.) Determined that DNA is acidic and high in phosphorous 9.) Conducted experiments showing that RNA can serve as the genetic material in some viruses 10.) Demonstrated that heat-killed material from bacteria could genetically transform live bacteria

1.) Franklin and Wilkins 2.) Kossel 3.) Hershey and Chase 4.) Chargaff 5.) Avery, MacLeod, and McCarty 6.) Watson and Crick 7.) Levene 8.) Miescher 9.) Fraenkel-Conrat and Singer 10.) Griffith

List the steps of DNA replication in order that they occur.

1.) Helicase unwinds the DNA double helix. 2.) Single-stranded DNA-binding proteins bind to each template strand. 3.) RNA primers are added. 4.) DNA polymerase synthesizes DNA. 5.) RNA primers are removed. 6.) DNA ligase joins DNA fragments together.

Describe the origin of chloroplasts and mitochondria in eukaryotic lineages through endosymbiosis.

1.) Host cell ingested aerobic bacteria. 2.) Divergence of early eukaryotes occurred. 3.) Two paths: -Host cell ingested cyanbacteria --> undigested bacteria evolved into chloroplasts. -Undigested bacteria evolved into mitochondria.

Describe the structure or function of mitochondria. There are two true statements.

1.) Mitochondria regulate apoptosis. 2.) The synthesis of adenosine triphosphate, ATP, occurs inside the mitochondria.

Place the type of translocation and sequences translocated next to each set of chromosomes. The * represents the centromere. Nonhomologous chromosomes: AB*CDEFG RS*TUVWX Translocations: 1.) AB*CD RS*TUVWXEFG 2.) AUVB*CDEFG RS*TWX 3.) AB*TUVFG RS*CDEWX 4.) AB*CWG RS*TUVDEFX

1.) Nonreciprocal translocation of EFG 2.) Nonreciprocal translocation of UV 3.) Reciprocal translocation of CDE and TUV 4.) Reciprocal translocation of DEF and W

1.) One example of non-Mendelian inheritance is uniparental inheritance. What is uniparental inheritance? 2.) What are some examples of genetic material that are uniparentally inherited in sexually reproducing eukaryotes?

1.) One parent transmits all genetic information to all offspring. 2.) Chloroplast DNA and mitochondria DNA

Fill in the blanks. 1.) In a circular bacterial chromosome, the structure of DNA is a _______ double helix. 2.) If DNA is twisted in the _______ direction, it becomes overwound. 3.) Overwinding results in _______ supercoiling. 4.) If DNA is twisted in the _______ direction, it becomes underwound. 5.) Underwinding results in _______ supercoiling. 6.) One effect of _______ supercoiling in bacterial chromosomes is to promote separation of the two strands of DNA in the double helix.

1.) Right-handed 2.) Right-handed 3.) Positive 4.) Left-handed 5.) Negative 6.) Negative

1.) What evidence supports the hypothesis that RNA was the genetic material early in evolutionary history? 2.) What is the reason scientists think DNA was selected over RNA as the most common genetic material?

1.) Some viruses have RNA genomes. RNA can catalyze enzymatic reactions. 2.) DNA is more stable than RNA.

Place the type of chromosomal mutation next to each set of chromosomes. The * represents the centromere. Wild-type: AB*CDEFG Mutations: 1.) AB*CDEFDEFG 2.) AB*DEFCDEFG 3.) AB*CDE 4.) AB*CGFED 5.) AEDC*BFG

1.) Tandem duplication of DEF 2.) Displaced duplication of DEF 3.) Deletion of FG 4.) Paracentric inversion that includes DEFG 5.) Pericentric inversion of BCDE

Suppose that a hapless graduate student has forgotten to label four different sample tubes that contained thermophilic archaea, bacteria, single-stranded DNA viruses, and double-stranded RNA viruses. The table below shows the nucleotide content of each sample, except for the nucleotide uracil, which is excluded. Label each unknown sample with the appropriate sample name. Sample#--G%--C%--A%--T% 1--31--31--19--19 2--17--17--33--33 3--19--31--23--27 4--21--21--29--0

1.) Thermophilic archaea 2.) Bacteria 3.) Single-stranded DNA virus 4.) Double-stranded RNA virus

The major contribution of Franklin and Wilkins to the study of DNA was ______.

An X-ray diffraction pattern

Describe how m-AMSA and other anticancer agents that target topoisomerase enzymes taking part in replication might lead to DNA breaks and chromosome rearrangements.

1.) m-AMSA inhibits the action of topoisomerase after the topoisomerase has generated double-strand breaks in the DNA. 2.) m-AMSA stabilizes the intermediate form of topoisomerase, which prevents the breaks from resealing, resulting in DNA damage.

Crossing over within a pericentric inversion produces chromosomes that have extra copies of some genes and no copies of other genes. The fertilization of gametes containing these duplication or deficient chromosomes often results in children with syndromes characterized by developmental delay, mental retardation, abnormal development of organ systems, and early death. One study examined individual sperm cells of a male who was heterozygous for a pericentric inversion on chromosome 8 and determined that crossing over took place within the pericentric inversion in 26% of the meiotic divisions. Assume that a man and a woman are phenotypically normal, but the woman is heterozygous for a pericentric inversion on chromosome 8. The man is karyotypically normal. What is the probability that this couple\'s child will inherit a duplicated or deficient chromosome 8 that results from crossing over within this pericentric inversion?

13%

The number of hydrogen bonds between complementary G--C pairs is ______.

3

Enter the complementary sequence to the following DNA strand. 5'- TGACGTGAT -3'

3'-ACTGCACTA-5'

Some people with Turner syndrome are 45,X/46,XY mosaics. How could this mosaicism arise?

A cell loses a Y chromosome soon after fertilization in an XY embryo.

Define euploidy.

A complete chromosome set or an exact multiple of the haploid chromosome set.

Which of the following relations will be found in the percentages of bases of a double-stranded DNA molecule? Select all that apply. A.) A+G=C+T B.) A/T=G/C C.) (A+G)/(C+T)=1.0 D.) A/G=C/T E.) A+T = G+C

A.) A+G=C+T B.) A/T=G/C C.) (A+G)/(C+T)=1.0

The bacterium Streptococcus pneumoniae has a virulent S strain and a nonvirulent R strain. The S strain is lethal to mice. The S strain contains a chemical factor that can transform the R strain to be virulent. The diagram shows a series of experiments conducted by injecting combinations of these strains into mice to identify the transforming factor. If DNA is the transforming factor, match the expected results of each experiment by placing the appropriate mouse image. A: R strain (nonvirulent) B: S strain (virulent) C: Heat-treated S strain D.) R strain and heat-treated S strain E.) R strain and heat-treated S strain with polysacchairdes, lipids, RNA, and proteins destroyed. F.) R strain and heat-treated S strain with polysacchairdes, lipids, RNA, proteins, and DNA destroyed.

A.) Alive B.) Dead C.) Alive D.) Dead E.) Dead F.) Alive

There are two types of nucleic acids, DNA and RNA. Nearly all organisms use DNA, not RNA, as the central repository for genetic information. Choose the statements that explain this phenomenon. A.) DNA has a double-stranded structure that ensures an accurate mechanism of duplication. B.) DNA is flexible and forms complex catalytic structures. C.) DNA is more resistant against enzymes that break down nucleic acids. D.) DNA contains cytosine as one of its nitrogenous bases. E.) DNA contains an -OH group at the 2' carbon.

A.) DNA has a double-stranded structure that ensures an accurate mechanism of duplication. C.) DNA is more resistant against enzymes that break down nucleic acids.

Which of the following single-stranded DNA sequences is most likely to form a stem-loop structure? A.) GACCGTATGCACGGTC B.) TCATAGGCGCCGTTCA C.) GGATCACGTTACCGCC D.) TAAGTACATTACCCCG

A.) GACCGTATGCACGGTC

Select the statements that describe the effect of copy number variation on human phenotypes. A.) Increase in the copy number of immunity genes can result in increased pathogen resistance. B.) A decrease in copy number can cause Mendelian autosomal disorders due to point mutations. C.) An increase in copy number can cause gene function loss due to chromosome breaks. D.) Copy number variations are associated with complex disorders such as autism. E.) Oncogene overexpression due to a gain in copy number can cause cancer.

A.) Increase in the copy number of immunity genes can result in increased pathogen resistance. D.) Copy number variations are associated with complex disorders such as autism. E.) Oncogene overexpression due to a gain in copy number can cause cancer.

Which of the following statements about polyploidy is NOT correct? A.) It is possible only between the members of the same species. B.) It often results in larger cell size. C.) It results from failure to separate a whole set of chromosomes during cell division. D.) It is a major mechanism by which new plant species have evolved. E.) It is found in many of the food crop plants we enjoy, such as bananas and strawberries.

A.) It is possible only between the members of the same species.

Select each of the characteristics that are key features of genetic material. A.) It must be able to replicate and transmit to progeny. B.) It must have observable characteristics that are heritable. C.) It must encode the blueprint to form proteins and other structures. D.) It must periodically mutate to generate variation. E.) It must differentiate in each cell type.

A.) It must be able to replicate and transmit to progeny. C.) It must encode the blueprint to form proteins and other structures. D.) It must periodically mutate to generate variation.

What characteristic is not necessary for a molecule that is the genetic material? A.) It must perform the action associated with the phenotype. B.) It must have the ability to replicate faithfully. C.) It must contain complex information. D.) It must be variable. E.) It must encode the phenotype.

A.) It must perform the action associated with the phenotype.

Which of the following statements describes purines and pyrimidines in DNA molecules? A.) Pyrimidines consist of a one-ring structure. B.) Pyrimidines form covalent bonds with purines. C.) Pyrimidines form hydrogen bonds with purines. D.) Adenine and guanine are pyrimidines. E.) Purines form hydrogen bonds with purines.

A.) Pyrimidines consist of a one-ring structure. C.) Pyrimidines form hydrogen bonds with purines.

Which of these is an example of a sequence of bases in an RNA molecule that will produce a hairpin structure? Select all that apply. A.) UGCGAUACUCAUCGCA B.) TGCGATACTCATCGCA C.) CGCGCAAAGCGCG D.) AAUAAUUUCGGAGCGC E.) AUCGGGCCCAAGUCG

A.) UGCGAUACUCAUCGC C.) CGCGCAAAGCGCG

Which of the following statements about primers are correct? Select all that apply.

ALL OF THEM: -synthesized by an enzyme called primase. -synthesized by DNA polymerase alpha. -needed for the start of DNA synthesis. -provide a 3-OH group for attachment of DNA nucleotides.

Red-green color blindness is a human X-linked recessive disorder. The normal allele, XB, is dominant to the mutant allele, Xb. Jill has normal color vision, but her father is color blind. Jill marries Tom, who also has normal color vision. Jill and Tom have a daughter who has Turner syndrome and is color blind. How and from whom did the daughter inherit color blindness?

An ovum carrying Xb followed by fertilization by sperm from a paternal nondisjunction event.

The Notch mutation is a deletion on the X chromosome of Drosophila melanogaster. Female flies heterozygous for Notch have an indentation on the margins of their wings. Notch is lethal in the homozygous and hemizygous conditions. The Notch deletion covers the region of the X chromosome that contains the locus for white eyes, an X-linked recessive trait. Determine the phenotypes and proportions of progeny produced by the crosses listed. A.) Red-eyed Notch female x white-eyed male B.) White female x red male C.) White female x white male

B only: 1/3 red females C only: 1/3 white males, 1/3 white females A+B only: 1/3 wild-type females, 1/3 wild-type males A+C only: 1/3 white females

Which of the following statements describe mosaicism? A.) The skin on a person's face and arms becomes much darker than the skin on the rest of the body after a summer of working outdoors. B.) A child with the phenotypic features characteristic of Down syndrome has a mixture of normal cells and cells with three copies of chromosome 21. C.) A wheelchair-bound person's leg muscles are weaker than her arm muscles. D.) A cancerous tumor develops in a smoker's lung. E.) A tortoiseshell cat has patches of orange and black fur.

B.) A child with the phenotypic features characteristic of Down syndrome has a mixture of normal cells and cells with three copies of chromosome 21. D.) A cancerous tumor develops in a smoker's lung. E.) A tortoiseshell cat has patches of orange and black fur.

Select the statements that explain why duplication is a driving force for evolution and the generation of new genes. A.) Duplication of a gene segment always results in novel phenotypes. B.) Genes duplicate and then diverge from the original sequence to create novel genes. C.) Duplicated genes provide extra copies of DNA that are not constrained by an essential function. D.) Changes in gene function can occur when random fixed mutations are introduced into a new chromosomal environment.

B.) Genes duplicate and then diverge from the original sequence to create novel genes. C.) Duplicated genes provide extra copies of DNA that are not constrained by an essential function. D.) Changes in gene function can occur when random fixed mutations are introduced into a new chromosomal environment.

Besides the nuclear DNA, certain organelles contain DNA of their own. Which of the following organelle(s) contain DNA of their own? Select all that apply. A.) Endoplasmic reticulum B.) Mitochondria C.) Chloroplasts D.) Golgi apparatus

B.) Mitochondria C.) Chloroplasts

Which of the following statements about aneuploidy is correct? A.) The rarest aneuploidies in humans are of the sex chromosomes. B.) One form of aneuplody is a loss of both members of a homologous pair of chromosomes. C.) Most autosomal aneuploids develop normally and have a normal life span. D.) Aneulploidy is a change in number of chromosome sets.

B.) One form of aneuplody is a loss of both members of a homologous pair of chromosomes.

Lesch-Nyhan syndrome is an X-linked, recessive condition caused by mutation of the HPRT1 gene responsible for purine metabolism. The syndrome is characterized by juvenile-onset gout, involuntary muscle movements, and behavioral disorders. A mother and father have a young daughter who was diagnosed with Lesch-Nyhan syndrome. No one in the father\'s family was ever diagnosed with the syndrome. The mother\'s maternal grandfather was diagnosed with Lesch-Nyhan syndrome, but neither one of her parents was diagnosed with the condition. Select all the descriptions that could explain how their daughter inherited Lesch-Nyhan syndrome. A.) The father is a carrier of the Lesch-Nyhan mutation. The daughter inherited one X chromosome with the Lesch-Nyhan mutation from her father, and no X chromosome from her mother. B.) The daughter inherited two X chromosomes with the Lesch-Nyhan mutation. Nondisjunction of the mother\'s X chromosomes occurred during meiosis, and the daughter inherited no X chromosome from her father. C.) The father did not contribute a sex chromosome to his daughter due to nondisjunction of the sex chromosomes. The daughter is XO and her only X chromosome came from her mother, who was a carrier. D.) The daughter could not have inherited Lesch-Nyhan because neither of her parents have the disease. The fact that her great-grandfather had Lesch-Nyhan is a coincidence.

B.) The daughter inherited two X chromosomes with the Lesch-Nyhan mutation. Nondisjunction of the mother\'s X chromosomes occurred during meiosis, and the daughter inherited no X chromosome from her father. C.) The father did not contribute a sex chromosome to his daughter due to nondisjunction of the sex chromosomes. The daughter is XO and her only X chromosome came from her mother, who was a carrier.

Which of the following statements about chromosome inversions is correct? A.) They lead to an increase in crossovers. B.) They can reduce the number of chromosomes in a cell. C.) They flip a segment of a chromosome 180 degrees. D.) They do not affect gene expression.

C.) They flip a segment of a chromosome 180 degrees.

Which of the following statements about euchromatin and heterochromatin are correct? Select all that apply. A.) Heterochromatin is less condensed than euchromatin. B.) The majority of transcription takes place on euchromatin. C.) Euchromatin undergoes condensation and decondensation throughout the cell cycle. D.) Most genes are present in heterochromatin. E.) Euchromatin largely consists of repeated sequences.

B.) The majority of transcription takes place on euchromatin. C.) Euchromatin undergoes condensation and decondensation throughout the cell cycle.

Which of the following are true of endosymbiotic theory? A.) provides insight about why mitochondria can survive outside of a eukaryotic cell B.) states that an ancestral eukaryotic cell engulfed an aerobic protobacteria C.) explains why mitochondria contain circular DNA similar to bacteria D.) explains the origin of some eukaryotic organelles, such as chloroplasts E.) explains the origin of all organelles found within a eukaryotic cell

B.) states that an ancestral eukaryotic cell engulfed an aerobic protobacteria C.) explains why mitochondria contain circular DNA similar to bacteria D.) explains the origin of some eukaryotic organelles, such as chloroplasts

A key discovery leading to the structure of DNA was done by Chargaff. He found that ____. Select all that apply. A.) that the amount of A equals the amount of C, and the amount of G equals the amount of T B.) that the amount of A equals the amount of T, and the amount of G equals the amount of C C.) that the amount of A equals the amount of G, and the amount of C equals the amount of T D.) the tetranucleotide hypothesis was false.

B.) that the amount of A equals the amount of T, and the amount of G equals the amount of C D.) the tetranucleotide hypothesis was false.

Which of the following statements about chromosome translocation is correct? A.) They do not affect chromosome number. B.)They can affect gene expression by moving a gene under the control of a different promoter. C.) They only take place within a chromosome. D.) Translocation and "crossing over" refer to the same phenomenon.

B.)They can affect gene expression by moving a gene under the control of a different promoter.

List the steps of prokaryotic DNA replication in order, from the bacterium initiating DNA replication to DNA-replication termination.

Bacterium initiating DNA replication: 1.) The only origin of replication is bound by DNAa protein. 2.) The upstream region melts, and helicase binds and unwinds DNA. 3.) RNA primers are added to provide a 3' end of elongation. 4.) 5' to 3' synthesis of the leading strand and short lagging strand is carried out by DNA polymerase. 5.) DNA replaces RNA and lagging strands are joined. 6.) Tus proteins stops replication forks from crossing each other and ends synthesis. DNA replication terminated.

The eukaryotic protein critical for organizing chromatin structure is histone. Which of the following histone proteins is not included in the histone "core" that is often described as the "beads"? A.) H4 B.) H2A C.) H1 D.) H2B E.) H3

C.) H1

During meiosis, errors can be made during chromosome replication. Which term describes a mutation where a chromosome breaks, and its genetic material is reinserted in a different orientation? A.) Frameshift B.) Duplication C.) Inversion D.) Isochromosome

C.) Inversion

Which of the following statements describes the semiconservative model of DNA replication correctly? A.) It proposes that the entire double-stranded DNA molecule serves as a template for a whole new molecule of DNA. B.) It proposes that both nucleotide strands break down into fragments, which then serve as templates for the synthesis of new DNA molecules. C.) It proposes that the two nucleotide strands unwind and each serves as a template for a new DNA molecule.

C.) It proposes that the two nucleotide strands unwind and each serves as a template for a new DNA molecule.

Which statement about cellular DNA is incorrect? A.) DNA exists in the cell as very long, tightly packed molecules. B.) Supercoiling allows cellular DNA to be packed into a small space. C.) Most cellular DNA is positively supercoiled. D.) Supercoiling of cellular DNA is controlled by topoisomerases. E.) Supercoiling makes the separation of the two strands of DNA easier for replication and transcription.

C.) Most cellular DNA is positively supercoiled.

How does chromosome compaction differ during metaphase and interphase in eukaryotes?

Chromosomes are less compacted in interphase than in metaphase.

What is the key feature of DNA that allows it to be copied?

Complementary base pairing

About 0.3% of human live births are trisomic. In contrast, only 0.02% of human live births are monosomic. Select the best explanation for why the occurrence of monosomics is less than that of trisomics. A.) Gene dosage imbalance is more likely to lead to spontaneous abortion in monosomics than in trisomics. B.) Mitosis is less likely to be completed correctly in monosomic gamates. C.) Meiotic nondisjunction rarely produces monosomic gamates. D.) Deleterious recessive alleles are always expressed on the monosomic chromosome but not on the trisomic chromosomes.

D.) Deleterious recessive alleles are always expressed on the monosomic chromosome but not on the trisomic chromosomes.

Which of the following descriptions about prokaryotic versus eukaryotic DNA replication is not correct? A.) In prokaryotes, there is only a single replication bubble; in eukaryotes, there are many. B.) In both prokaryotes and eukaryotes, the new and old DNA strands are assembled in antiparallel manner. C.) In both prokaryotes and eukaryotes, the DNA undergoes negative supercoiling during replication. D.) In prokaryotes, the DNA replication is unidirectional; in eukaryotes, the replication is bidirectional. E.) In prokaryotes, there is only one origin of replication; in eukaryotes, there are many.

D.) In prokaryotes, the DNA replication is unidirectional; in eukaryotes, the replication is bidirectional.

Which of the following statements about Down syndrome is correct? A.) It never runs in the family as it is based on a random aneuploidy event. B.) The probability of a child having it does not correlate with maternal age. C.) The primary cause of it is the Robertsonian translocation. D.) Trisomy of chromosome 21 is well tolerated enough to give rise to fully developed individuals.

D.) Trisomy of chromosome 21 is well tolerated enough to give rise to fully developed individuals.

What property of the DNA molecule explains the necessity for Okazaki fragments?

DNA is antiparallel.

Which of the following components required for prokaryotic DNA replication is not involved in "unwinding" the DNA template?

DNA ligase

When a solution containing double-stranded DNA is heated, the hydrogen bonds that hold the two strands can be weakened and eventually broken, separating the strands completely. This process is called ______.

Denaturation

Which of the following was not shown by Watson and Crick's model of DNA? A.) One adenine would pair with one thymine. B.) There could be a means for DNA to easily replicate itself. C.) The strands run in opposite directions. D.) The helices are right-handed. E.) The bases face outside for easy access.

E.) The bases face outside for easy access.

Classify each feature as describing euchromatin, heterochromatin, or both.

Euchromatin: -loosely packed -is accessible to transcription machinery -is found in prokaryotes -is the major state of most genes Both: -is a state of DNA organization Heterochromatin: -tightly packed -is inaccessible to transcription machinery -is the major state of the inactive X chromosome

True or false: The C value, which indicates the amount of DNA in a haploid genome, always correlates to the complexity of the organism.

False

Frank has Klinefelter syndrome (47, XXY). His mother has normal skin, but his father has anhidrotic ectodermal dysplasia, an X-linked condition where the skin does not contain sweat glands. Frank has patches of normal skin and patches of skin without sweat glands. Complete the sentences. Some answers may be used more than once or not at all. Frank received the mutant chromosome from his __________. Nondisjunction occurred in his _________ during the _________ meiotic division.

Father; Father; First

DNA has unique properties that allow it to accurately retain genetic information, even after multiple rounds of replication. One aspect of DNA that allows it to accurately store genetic information is the base pairing from Chargaff's first rule of the four nucleotide bases. If the C content of a DNA molecule is 18%, what are the percentages of the remaining bases?

G = 18% T = 32% A = 32%

A structure formed by a single-stranded DNA or RNA molecule that has complementary sequences is a/an ________.

Hairpin

Most of the centromere and telomere structures consist of _____.

Heterochromatin

Describe the reassembly of nucleosomes during replication.

Histones from the original DNA duplex are mixed with new histones on the two new DNA molecules.

Two brothers have X-linked red-green colorblind vision, and their parents have normal color vision. The first brother's karyotype is 47, XXY (Klinefelter syndrome), and the second brother's karyotype is 46, XY. In which parent and in what cell division phase did the first brother's chromosomal nondisjunction occur? Assume no recombination.

In the mother, in meiosis II.

The sugar in DNA is called deoxyribose because it _____.

Is missing a 2'-OH group.

What does the conservative model of DNA replication propose?

It proposes that the entire double-stranded DNA molecule serves as a template for a whole new molecule of DNA.

When a circular DNA gets under-rotated by the action of cellular enzymes, the DNA is said to exhibit _____.

Negative supercoiling

Classify each of the descriptions below as a characteristic of mitochondria only, chloroplasts only, or both mitochondria and chloroplasts.

Mitochondria only: -perform cellular respiration -found in animals Chloroplasts only: -perform photosynthesis -contain grana Both: -contain DNA -produce energy -mobile within the cell

A distinct clump of prokaryotic DNA observed via electron microscopy is referred to as a _______.

Nucleoid

Suppose a scientist grows cells in a medium that contains amino acids labeled with a heavy isotope. She isolates histone octamers from some of these cells and subjects the isolated proteins to density-gradient centrifugation. The centrifugation yields a single band of heavy isotope-labeled histones near the bottom of the tube. The scientist then transfers the remaining cells to a medium that contains amino acids labeled with a lighter isotope. She isolates new histone octamers from the culture after cells replicate in this medium and subjects these proteins to another round of density-gradient centrifugation. How many bands does the scientist expect to see in the second round of density-gradient centrifugation if all original histone proteins remain on one strand of DNA and new histones attach to the other strand during replication?

One lower band containing the original histone octamers and one higher band containing the new histone octamers.

A strong covalent bond between adjacent nucleotides is a/an ______.

Phosphodiester bond

List the events of gene conversion of wild-type allele G to mutant allele g during meiotic recombination.

Recombination in meiosis: 1.) A heteroduplex is formed between G and g alleles. 2.) Mismatched bases in the heteroduplex trigger mismatch repair. 3.) Mismatched bases are excised from the G allele. 4.) Gaps in the G allele sequence are filled by copying the g allele. 5.) The wild-type G allele is converted to the mutant g allele. Gene conversion.

A man has a large inversion on one of his chromosomes. How might this impact his offspring?

Severe phenotypic abnormalities caused by unbalanced chromatids.

Suppose the following data is collected for an unknown nucleic acid. Nitrogenous base--Comp. % A--28 C--18 G--26 T--0 U--28 Identify the unknown nucleic acid.

Single-stranded RNA

Arrange the features of eukaryotic chromosome packaging in order from the smallest unit to the largest unit.

Smallest--> base pairs, nucleosome, 30nm fiber, chromosome, genome <--Largest

What terms describes the tertiary structural organization of chromosomal DNA that allows the long strand to be packed and fit into the cytoplasm of the cell?

Supercoiling

True or false: mtDNA and cpDNA contain rRNA and tRNA genes of their own for their organelle-specific functions.

True

Match the definitions to the appropriate terms that describe the number of chromosomes.

Tetraploid --> four homologues of each chromosome. Tetrasomic --> two extra copies of a specific chromosome. n = 4 --> a genome composed of four unique chromosomes.

In experiments involving tobacco mosaic virus, Fraenkel-Conrat and Singer demonstrated _____.

That in some cases RNA can be the genetic material.

What is the function of the centromere in the transmission of genetic information?

The attachment point for sister chromatids.

In the Hershey-Chase experiment, DNA was demonstrated to be the genetic material because the 32P label for DNA localized to ________.

The bacterial pellet

The Meselson and Stahl experiment starts with E.coli containing 15N/15N labeled DNA grown in 14N media. Which result did Meselson and Stahl observe by sedimentation equilibrium centrifugation to provide strong evidence for the semiconservative model of DNA replication?

The first generation has hybrid 15N/14N DNA, and the second generation has both hybrid 15N/14N DNA and 14N/14N DNA. No 15N/15N DNA was observed.

What did Griffith discover with his experiments?

The transforming principle in bacteria.

What contribution did James Watson and Francis Crick make to our understanding of DNA?

They modeled the structure of DNA based on the limited data available.

In Avery, MacLeod, and McCarty'\'s experiments, homogenates from heat-killed bacteria were treated with different enzymes, and then the ability of those homogenates to transform bacteria was assayed. Under which condition would transformation not occur?

Treatment with DNase

The following is a representation of a human karyotype. What type of genetic disorder is shown in this karyotype? Chromosome 13 has three copies

Trisomy

Familial Down syndrome is similar to primary Down syndrome in that it is caused by trisomy 21. However, in familial Down syndrome, all or part of the third copy of chromosome 21 has translocated onto another autosome, typically chromosome 14. In cases of familial Down syndrome, one of the parents of the affected child is often a carrier of a translocated chromosome. The translocation carrier parent does not have Down syndrome because he or she has a total of two copies of chromosome 21. Suppose that a woman is a translocation carrier of chromosome 21 on chromosome 14. She conceives six zygotes with a normal man who carries no aneuploidies. Match the description of the chromosomes inherited by each zygote with the viability of the zygote.

Viable normal, or translocation carrier: -two normal copies of 14, two normal copies of 21 -one normal copy of 14, one normal copy of 21, one 21 to 14 translocation Viable, with Down syndrome: -one 21 to 14 translocation, two normal copies of 21, one normal copy of 14 Inviable: -one normal copy of 14, two normal copies of 21 -two normal copies of 14, one normal copy of 21 -one 21 to 14 translocation, one normal copy of 21, two normal copies of 14

A left-handed form of DNA is the ______.

Z-DNA

Complete the sentence. Histone proteins ______.

associate with DNA and compact DNA within the nucleus.