biology

1.
Chromosomes and genes share all of the following characteristics except that

Possible Answers
A. they both undergo segregation during meiosis.
B. they are both present in pairs in all diploid cells.
C. they are both copied during the S phase of the cell cycle.
D. their copy numbers in the cell decrease after meiosis, and increase during fertilization.
E. they both pair up with their homologues during prophase of mitosis.



2.
When Thomas Hunt Morgan crossed his red-eyed F1generation flies 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?

Possible Answers
A. The involved gene was on the Y chromosome.
B. The involved gene was on an autosome.
C. Other male-specific factors influence eye color in flies.
D. The involved gene was on the X chromosome.
E. Other female-specific factors influence eye color in flies.



3.
How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?

Possible Answers
A. The two genes are linked.
B. The two genes are unlinked.
C. Both of the characters are controlled by more than one gene.
D. The testcross was improperly performed.
E. Recombination did not occur in the cell during meiosis.



4.
New combinations of linked genes are due to which of the following?

Possible Answers
A. mixing of sperm and egg
B. nondisjunction
C. independent assortment
D. crossing over
E. both A and C



5.
The reason that linked genes are inherited together is that

Possible Answers
A. alleles are paired.
B. chromosomes are unbreakable.
C. the number of genes in a cell is greater than the number of chromosomes.
D. genes align that way during metaphase I.
E. they are located on the same chromosome.



6.
What is the mechanism for the production of genetic recombinants?

Possible Answers
A. nondisjunction
B. crossing over and independent assortment
C. methylation of cytosine
D. X inactivation
E. deletions and duplications during meiosis



7.
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?

Possible Answers
A. orange female; orange male
B. tortoise shell female; tortoise shell male
C. orange female; black male
D. black female; orange male
E. tortoise shell female; black male



8.
Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila by showing that

Possible Answers
A. the entire Drosophila genome has approximately 400 map units.
B. the overall number of genes in Drosophila is a multiple of four.
C. Drosophila genes cluster into four distinct groups of linked genes.
D. Drosophila genes have, on average, four different alleles.
E. there are four major functional classes of genes in Drosophila.



9.
A human individual is phenotypically female, but her interphase somatic nuclei do not show the presence of Barr bodies. Which of the following statements concerning her is probably true?

Possible Answers
A. She has two Y chromosomes.
B. She has Turner syndrome.
C. She has Klinefelter syndrome.
D. She has the normal number of sex chromosomes.
E. She has an extra X chromosome.



10.
In his transformation experiments, Griffith observed that

Possible Answers
A. mutant mice were resistant to bacterial infections.
B. infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.
C. mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.
D. mice infected with a pathogenic strain of bacteria can spread the infection to other mice.
E. mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.



11.
Chargaff's analysis of the relative base composition of DNA was significant because he was able to show that

Possible Answers
A. the relative proportion of each of the four bases differs from species to species.
B. both B and C
C. the amount of A is always equivalent to T, and C to G.
D. the human genome is more complex than that of other species.
E. both A and C



12.
The DNA double helix has a uniform diameter because ________, which have two rings, always pair with ________, which have one ring.

Possible Answers
A. nucleotides; nucleoside triphosphates
B. deoxyribose sugars; ribose sugars
C. ribose sugars; deoxyribose sugars
D. pyrimidines; purines
E. purines; pyrimidines



13.
What kind of chemical bond is found between paired bases of the DNA double helix?

Possible Answers
A. sulfhydryl
B. hydrogen
C. covalent
D. phosphate
E. ionic



14.
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in its

Possible Answers
A. phosphate-sugar backbones.
B. complementary pairing of bases.
C. sequence of bases.
D. side groups of nitrogenous bases.
E. different five-carbon sugars.



15.
In an analysis of the nucleotide composition of DNA, which of the following is true?

Possible Answers
A. G + A = T + C
B. A = G and C = T
C. A = C
D. A + C = G + T
E. both C and D



16.
The strands that make up DNA are antiparallel. This means that

Possible Answers
A. base pairings create unequal spacing between the two DNA strands.
B. one strand is positively charged and the other is negatively charged.
C. the twisting nature of DNA creates nonparallel strands.
D. one strand contains only purines and the other contains only pyrimidines.
E. the 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.



17.
Which enzyme catalyzes the elongation of a DNA strand in the 5'---> 3' direction?

Possible Answers
A. topoisomerase
B. DNA ligase
C. primase
D. helicase
E. DNA polymerase



18.
What is the function of DNA polymerase?

Possible Answers
A. to unwind the DNA helix during replication
B. to degrade damaged DNA molecules
C. to rejoin the two DNA strands (one new and one old) after replication
D. to seal together the broken ends of DNA strands
E. to add nucleotides to the end of a growing DNA strand



19.
What kind of molecule or substance is the primer that is used to initiate the synthesis of a new DNA strand?

Possible Answers
A. protein
B. RNA
C. sulfur
D. DNA
E. phosphate



20.
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

Possible Answers
A. join Okazaki fragments together
B. unwind the parental double helix
C. catalyze the lengthening of telomeres
D. synthesize RNA nucleotides to make a primer
E. stabilize the unwound parental DNA



21.
Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because

Possible Answers
A. certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.
B. many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA.
C. metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.
D. enzymes are made of DNA, and affected individuals lack DNA polymerase.
E. genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.



22.
Which of the following represents a similarity between RNA and DNA?

Possible Answers
A. Both are found exclusively in the nucleus.
B. the presence of an OH group on the 2' carbon of the sugar
C. nucleotides consisting of a phosphate, sugar, and nitrogenous base
D. Both are double-stranded.
E. the presence of uracil



23.
The nitrogenous base adenine is found in all members of which group?

Possible Answers
A. proteins, ATP, and DNA
B. proteins, carbohydrates, and ATP
C. alpha glucose, ATP, and DNA
D. ATP, RNA, and DNA
E. proteins, triglycerides, and testosterone



24.
Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because

Possible Answers
A. RNA is much more stable than DNA.
B. RNA acts as an expendable copy of the genetic material, allowing the DNA to serve as a permanent, pristine repository of the genetic material.
C. A, B, and C
D. B and C only
E. many mRNA molecules can be transcribed from a single gene, increasing the potential rate of gene expression.



25.
A particular triplet of bases in the template strand of DNA is AGT. The corresponding codon for the mRNA transcribed is

Possible Answers
A. TCA.
B. AGT.
C. UGA.
D. ACU.
E. either UCA or TCA, depending on wobble in the first base



26.
A codon

Possible Answers
A. may code for the same amino acid as another codon.
B. is found in all eukaryotes, but not in prokaryotes.
C. catalyzes RNA synthesis.
D. consists of discrete amino acid regions.
E. consists of two nucleotides.



27.
RNA polymerase and DNA polymerase differ in that

Possible Answers
A. RNA polymerase binds to single-stranded DNA, and DNA polymerase binds to double-stranded DNA.
B. RNA polymerase uses RNA as a template, and DNA polymerase uses a DNA template.
C. RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis.
D. RNA polymerase is much more accurate than DNA polymerase.
E. RNA polymerase does not need to separate the two strands of DNA in order to synthesize an RNA copy, whereas DNA polymerase must unwind the double helix before it can replicate the DNA.



28.
What are the coding segments of a stretch of eukaryotic DNA called?

Possible Answers
A. introns
B. transposons
C. replicons
D. exons
E. codons



29.
Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes

Possible Answers
A. fusion with other newly transcribed mRNA.
B. excision of introns.
C. union with ribosomes.
D. fusion into circular forms known as plasmids.
E. linkage to histone molecules.



30.
All of the following are directly involved in translation except

Possible Answers
A. ribosomes.
B. mRNA.
C. aminoacyl-tRNA synthetase enzymes.
D. tRNA.
E. DNA.



31.
What are ribosomes composed of?

Possible Answers
A. mRNA, rRNA, and protein
B. mRNA, tRNA, rRNA, and protein
C. both rRNA and protein
D. proteins only
E. rRNA only



32.
What is the most abundant type of RNA?

Possible Answers
A. mRNA
B. hnRNA
C. pre-mRNA
D. tRNA
E. rRNA



33.
When does translation begin in prokaryotic cells?

Possible Answers
A. after a transcription initiation complex has been formed
B. as soon as the DNA introns are removed from the template
C. after the 5' caps are converted to mRNA
D. once the pre-mRNA has been converted to mRNA
E. during transcription



34.
During translation, chain elongation continues until what happens?

Possible Answers
A. No further amino acids are needed by the cell.
B. The polypeptide is long enough.
C. The ribosomes run off the end of mRNA.
D. A stop codon is encountered.
E. All tRNAs are empty.



35.
Tobacco mosaic virus has RNA rather than DNA as its genetic material. In a hypothetical situation where RNA from a tobacco mosaic virus is mixed with proteins from a related DNA virus, the result could be a hybrid virus. If that virus were to infect a cell and reproduce, what would the resulting "offspring" viruses be like?

Possible Answers
A. the related DNA virus
B. tobacco mosaic virus
C. a hybrid: tobacco mosaic virus RNA and protein from the DNA virus
D. a hybrid: tobacco mosaic virus protein and nucleic acid from the DNA virus
E. a virus with a double helix made up of one strand of DNA complementary to a strand of RNA surrounded by viral protein



36.
Avery and his colleagues purified various chemicals from pathogenic bacteria and showed that ________ was (were) the transforming agent.

Possible Answers
A. protein
B. carbohydrates
C. lipids
D. DNA
E. phage



37.
What does transformation involve in bacteria?

Possible Answers
A. the creation of a strand of RNA from a DNA molecule
B. assimilation of external DNA into a cell
C. the type of semiconservative replication shown by DNA
D. the infection of cells by a phage DNA molecule
E. the creation of a strand of DNA from an RNA molecule



38.
A man who carries an X-linked allele will pass it on to

Possible Answers
A. half of his sons.
B. half of his daughters.
C. all of his children.
D. all of his daughters.
E. all of his sons.



39.
Most calico cats are female because

Possible Answers
A. the Y chromosome has a gene blocking orange coloration.
B. a male inherits only one of the two X-linked genes controlling hair color.
C. multiple crossovers on the Y chromosome prevent orange pigment production.
D. the males die during embryonic development.
E. only females can have Barr bodies.



40.
Males are more often affected by sex-linked traits than females because

Possible Answers
A. X chromosomes in males generally have more mutations than X chromosomes in females.
B. males are hemizygous for the X chromosome.
C. mutations on the Y chromosome often exacerbate the effects of X-linked mutations.
D. male hormones such as testosterone often exacerbate the effects of mutations on the X chromosome.
E. female hormones such as estrogen often compensate for the effects of mutations on the X.

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