Biology 123 SI- Dr. Raut’s Class
Mock Exam 3
1. A man who can roll his tongue and a woman who cannot roll her tongue have a son who can
roll his tongue (R=can roll tongue; r= cannot roll tongue). The son is curious about whether his
father is homozygous or heterozygous for the tongue-rolling trait. Which of the following facts
would allow him to know?
A. The son’s own daughter cannot roll her tongue.
B. The son submits his own blood sample to a local genotyping lab, and they establish that he is
heterozygous for the trait.
C. His father’s mother cannot roll her tongue.
D. The son’s sister is a tongue roller.
E. His paternal grandfather and his paternal grandmother can both roll their tongues.
2. True or false: The law of independent assortment states that each pair of alleles segregates
independently of each other pair of alleles during gamete formation.
3. In ______________, one gene has several phenotypic affects.
A. Epistasis
B. Polygenic inheritance
C. Polydactyly
D. Pleiotropy
E. None of the above.
4. Which of the following matings cannot produce a child with the blood type O? The letter
refers to the blood types (phenotypes).
A. O x O
B. O x AB
C. A x A
D. A x B
E. All of the above could produce a child with the blood type O.
5. In wheat kernels, the R allele confers red color and the r allele brown kernel color. The B gene
controls expression of the R gene. Corn of genotype bb will have white kernels. If a red kernel
wheat plant with the genotype RrBb is fertilized by a brown weat plant rrBb, what fraction of the
wheat plants will have red kernels? (Note: bb codes for no color or white).
A. 6/16
B. 8/16
C. 4/16
D. 7/16
E. None of the above.
6. Physically, what are different alleles?
A. Different alleles are different phenotypes for a particular character.
B. Different alleles are different DNA sequences found at the same locus on sister chromatids.
C. Different alleles are different particles found in gametes.
D. Different alleles are different DNA sequences found at the same locus on homologous
chromosomes.
E. None of the above.
7. The pedigree for a particular family is shown below.
Is the trait recessive or dominant? Is the mother of the first generation homozygous or
heterozygous?
A. recessive/ homozygous
B. recessive heterozygous
C. dominant/ homozygous
D. dominant/ heterozygous
E. There is not enough information available to answer the question.
8. What chromosomal alteration is responsible for the cri du chat syndrome?
A. translocation
B. inversion
C. duplication
D. genetic imprinting
E. deletion
9. Which of the following is true regarding sex linked genes?
A. Since women have two X chromosomes, they are twice as likely to express diseases that are
found on the X chromosome.
B. Women are more likely to suffer from color blindness.
C. Men are more likely to express diseases that are found on the X chromosome.
D. The X chromosome in men is typically inactivated in the form of a barr body, because men do
not need their X chromosome.
E. None of the above.
10. In a particular experiment studying the linked genes in hamsters fur color (brown, B, is
dominant to blonde b) and fur thickness (thick, T, is dominant to thin t), a BbTt mouse is bred
with a bbtt mouse. There are 20 total offspring with 3 recombinant brown hamsters with thin hair
and 2 recombinant blonde hamsters with thick hair. What is the recombination frequency?
A. 25%
B. 15%
C. 10%
D. 45%
E. 30%
11. On a linkage map, eye color and eye shape are 56 map units apart, while eye color and vision
are 15 map units apart. Which will have a higher rate of recombinants?
A. Eye color and eye shape
B. Eye color and vision
C. What is a map unit?
D. None of the above.
12. The chromosome theory of inheritance states that ________________.
A. genes occupy specific positions on chromosomes
B. chromosomes assort independently during meiosis
C. homologous chromosomes segregate from each other during meiosis.
D. B and C
E. All of the above.
13. 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. Chromosome 21 is a sex chromosome, and 3 and 16 are not.
B. There are probably more genes on chromosome 21 than on the others.
C. Nondisjunction of chromosomes 3 and 16 probably occurs much less frequently.
D. Extra copies of other chromosomes are probably fatal to the developing embryo.
E. Down syndrome is not more common, just more serious.
14. Variation of phenotype depending on whether an allele is inherited from the mother or the
father is an example of _____________.
A. inheritance of organelle genes
B. genomic imprinting
C. X inactivation
D. aneuploidy
E. polyploidy
15. How many Barr bodies would be observed in the nucleus of an XYY individual?
A. 0
B. 1
C. 2
D. 3
E. It would vary from cell to cell.
16. It is proposed that a certain disorder affecting the inner ear is caused by mitochondrial DNA.
Which of the following observations would be the most decisive evidence against this idea?
A. Females and males have the disorder in equal numbers.
B. Fathers with the disorder pass it on to all their children, but mothers with the disorder do not
pass it along.
C. Mothers pass the disorder on to their offspring, but fathers do not.
D. The precise cause of the disorder is found to involve the nervous system.
E. All of the above would be evidence against mitochondrial inheritance of this condition.
17. Which of the following enzyme is not correctly paired with its function?
A. Single-strand proteins-keep separated strands of DNA from reconnecting
B. Topoisomerase- helps to relieve the strain off of the rest of the strand of DNA
C. Helicases- rewind the double helix after replication
D. Primase- synthesizes a small RNA segment called a primer
E. All of the above are paired correctly.
18. DNA polymerase adds nucleotides to the _______ of the leading strands and to the ________
of the lagging strands.
A. 5’ end….. 5’ end
B. 5’ end…… 3’ end
C. 3’ end…… 5’ end
D. 3’ end…… 3’ end
E. sugar group….. phosphate group
19. What is the basis for the difference in how the leading and lagging strands of DNA molecules
are synthesized?
A. DNA ligase works only in the 3’ toe 5’ direction.
B. The origins of replication occur only at the 5’ end.
C. Polymerase can work on only one strand at a time.
D. Helicases and single-strand binding proteins work at the 5’ end.
E. DNA polymerase can join new nucleotides only to the 3’ end of a growing strand.
20. How are Okazaki fragments connected?
A. The nucleotides are in close enough proximity that they form together spontaneously.
B. DNA ligase joins the fragments together.
C. DNA polymerase joins the fragments together as the primer is replaced.
D. The cell heats up during DNA replication to ensure the fragments have enough energy to
bond together.
E. The Okazaki fragments don’t have to be connected.
21. Which of the following is true regarding how mistakes are fixed in DNA replication?
A. Nuclease cuts out the faulty DNA sequence.
B. DNA polymerase lays down new DNA to replace the faulty sequence.
C. DNA ligase seals the 3’ end of the new DNA to the 5’ end of the existing DNA.
D. All of the above are true.
E. None of the above are true.
22. A sample of DNA is composed of 28% Thymine. How much Guanine is present in the
sample?
A. 22%
B. 72%
C. 28%
D. 50%
E. None of the above.
23. Which of the following statements about replication origins is correct?
A. In both prokaryotes and eukaryotes, replication proceeds in both directions from each origin.
B. The two strands of DNA at the origin are separated, allowing the formation of a replication
bubble.
C. Bacterial chromosomes have a single origin, but eukaryotic chromosomes have many origins.
D. In eukaryotic cells, the many replication bubbles fuse once replication is complete.
E. All of the above.
24. Which is true regarding the recognized model of DNA replication?
A. The conservative model is recognized.
B. Of the two daughter DNA double-strands one is composed completely of paternal DNA and
one is composed completely of new DNA.
C. The semi-conservative model is recognized.
D. In each daughter DNA double-strand, one strand is composed of paternal DNA and the other
strand is composed of new DNA.
E. A and B
F. C and D
25. Telomeres _______________.
A. are shorter in younger individuals
B. remain the same regardless of the frequency of cell division
C. get shorter with continued cell division
D. code for important genes
E. get longer with continued cell division
26. Why are there only 45 tRNA, but 61 sense codons?
A.TRNA is not responsible for bringing in all amino acids.
B. Wobble pairing at the 3rd codon means that more than one tRNA can correspond to the same
codon.
C. Only 45 of the sense codons code for amino acids.
D. All of the above.
E. None of the above.
27. True or false: Only one ribosome can work on a single mRNA at a time.
28. A cell biologist found that two different proteins with largely different structures were
translated from two different mRNAs. These mRNAs, however, were transcribed from the same
template within the cell nucleus. Which mechanism below could best account for this?
A. A point mutation might have altered the gene.
B. The two proteins have different functions in the cell.
C. Different systems of DNA unpacking could result in two different mRNAs.
D. Exons from the same gene could be spliced in different ways to make different mRNAs.
E. Different transcription factors were involved in the transcription of the two mRNAs.
29. The number of nucleotide bases “read” together on the mRNA to designate each amino acid
is _______; this unit is called a(n) _______.
A. three…. triose
B. two…. dipeptide
C. two…. anticodon
D. one…. amino acid
E. three… codon
30. Which of the following is NOT true regarding eukaryotic transcription?
A. The promotor is the location where RNA polymerase binds.
B. The promotor follows the sequence GAGA.
C. Transcription factors are special proteins that help RNA polymerase bind.
D. The promotor, transcription factors, and RNA polymerase form the transcription initiation
complex.
E. All of the above are true.
31. What happens directly after a tRNA moves to the P site?
A. It leaves the ribosome.
B. It transfers its growing peptide to the amino acid on the tRNA in the A site.
C. It accepts the growing peptide from the tRNA in the A site.
D. The ribosome breaks apart and protein synthesis ceases.
E. None of the above.
32. Which of the following is NOT true of RNA processing?
A. Nucleotides may be added at both ends of the RNA.
B. A primary transcript is often much longer than the final RNA molecule that leaves the
nucleus.
C. RNA splicing can be catalyzed by splicesomes.
D. The poly A tail often assists in helping the mRNA find its way out of the nucleus and to a
ribosome.
E. All of the above are true.
33. What mutation has the smallest effect on the cell?
A. silent
B. frameshift
C. deletion of an entire codon
D. nonsense
E. missense
34. The anticodon of a particular tRNA molecule is
A. complementary to the corresponding triplet in rRNA.
B. the part of tRNA that bonds to a specific amino acid.
C. complementary to the corresponding mRNA codon.
D. catalytic, making tRNA a ribozyme.
E. changeable, depending on the amino acid that attaches to the tRNA.
35. Which of the following is true regarding the attachment of an amino acid to a tRNA?
A. In the process one ATP loses two phosphate groups.
B. Aminoacyl-tRNA synthetase is the enzyme.
C. The tRNA goes into the enzyme first, followed by the amino acid and ATP.
D. A and B
E. All of the above.
36. What is the segment of DNA that controls the expression of a gene in the operon concept?
A. Promotor
B. Operator
C. Repressor
D. Regulatory gene
E. Corepressor
37. True or false: Both the trp operon and the lac operon are examples of repressible operons.
****** The lac operon is an inducible operon
38. What is the primary difference between the lac operon and the trp operon?
A. The lac operon has a repressor that stays in the active state unless an induce puts it into an
inactive form, while the trp operon stays in the inactive form unless a corepressor puts it into an
active form.
B. The trp operon has a repressor that stays in the active state unless an induce puts it into an
inactive form, while the lac operon stays in the inactive form unless a corepressor puts it into an
active form.
C. The lac operon is a repressible operon, while the trp operon is not.
D. The trp operon is a repressible operon, while the lac operon is not.
E. Both A and D