A man and woman, both phenotypically normal, have a child who has red-green colorblindness (a sex-linked condition). Which of the following is most likely to be true?
a. the child is female and the mother is a carrier
b. the child is female and the paternal grandfather was color-blind
c. the child is male and the mother is a carrier
d. the child is male and the mother is color-blind
Hemophilia is a sex-linked trait. A man and a woman, neither of whom suffer from hemophilia, have a daughter with hemophilia. Which of the following could explain this event?
a. the paternal grandmother was a carrier
b. the paternal grandfather was a carrier
c. the daughter is also color-blind
d. the mother was a carrier and a mutation occurred in the father's gametes
Duchenne muscular dystrophy is a sex-linked condition. If a normal man marries a woman who is heterozygous for this condition, what percentage of their expected offspring would be expected to have Duchenne muscular dystrophy?
a. 25 percent
b. 50 percent
c. 75 percent
d. 100 percent
Coat color in calico cats and sweat gland mosaicism in humans are consequences of:
a. x-chromosome inactivation
b. polypoloidy
c. sex-linkage
d. fragile-x syndrome
Conditions such as those described in the previous questions are most commonly observed in:
a. hemizygous males
b. heterozygous females
c. homozygous males
d. polyploid individuals
The two strands of DNA are held together by ? between the nitrogenous bases.
a. covalent bonds
b. ester linkages
c. hydrogen bonds
d. thymine dimers
Which of the following are differences between DNA and RNA?
a. DNA contains deoxyribose whereas RNA contains ribose
b. RNA contains uracil whereas DNA contains thymine
c. DNA is usually single-stranded whereas RNA is double-stranded
d. Both a and b, but not c
e. Both a and c, but not b
Which of the following nucleotide bases is not a pyrimidine?
a. adenine
b. cytosine
c. uracil
d. thymine
In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?
a. A = G
b. A + G = C + T
c. A + T = G + T
d. A = C
e. G = T
Given: human DNA is composed of approximately 20 percent cytosine. What is the approximate percentage of adenine?
a. 20
b. 30
c. 50
d. 60
Arrange the following items involved in DNA replication in the correct chronological order: (1) DNA ligase (2) DNA polymerase (3) helicase (4) RNA primase (5) single-strand binding proteins.
a. 3-1-5-4-2
b. 4-2-3-1-5
c. 1-3-4-2-4
d. 3-5-4-2-1
What is the basis for the difference in the synthesis of the leading and lagging strands of DNA molecules?
a. The origins of replication occur only at the 5' end.
b. Helicases and single-strand binding proteins work only at the 5' end.
c. DNA polymerase can join new nucelotides only to the 3' end of a growing strand.
d. DNA ligase works only in the 3' to 5' direction.
e. Polymerase can only work on one strand at a time.
During DNA replication, DNA polymerase:
a. Synthesizes the new DNA strand in a 3' to 5' direction.
b. Moves along the template parental strand in a 5' to 3' direction.
c. Adds bases to the 5' end of an existing strand
d. Synthesizes on the leading strand continuously.
e. None of the above
All of the following are transcribed from DNA except:
a. exons
b. introns
c. tRNA
d. rRNA
e. promoter
Events during mRNA processing include:
a. Addition of a 5' cap
b. Addition of a Poly(T) tail
c. Removal of exons and splicing together of introns
d. Both a and c
e. None of the above
Which of the following are functions of the tail added to the 3' end of the mRNA primary transcript?
a. prevents degradation from enzymes
b. helps the ribosome recognize the start site
c. facilitates transport from cytoplasm to nucleus
d. all of the above
Which of the following is transcribed and then translated to form a protein product?
a. gene for tRNA
b. intron
c. promoter
d. gene for rRNA
e. all of the above
f. none of the above
Place the following events in the synthesis of a polypeptide in the proper order. (1) A peptide bond forms. (2) A tRNA matches its anticodon to the codon of the A site. (3) A tRNA translocates from the A to the P site, and an unattached tRNA leaves the ribosome from the E site. (4) The large subunit attaches to the small subunit and the initiator tRNA fits in the P site. (5) A small subunit binds to an mRNA and an initiator tRNA.
a. 4-5-3-2-1
b. 4-5-2-1-3
c. 5-4-3-2-1
d. 5-4-1-2-3
e. 5-4-2-1-3
tRNA:
a. delivers amino acids to ribosomes
b. picks up genetic messages from rRNA
c. synthesizes mRNA
d. none of the above
Given the DNA template strand 3' - ACGTTACAGCGTATC - 5', what would be the composition of the resulting polypeptide? (Use a codon table for this)
a. Thr - Leu - Gln - Arg - Ile
b. Cys - Asn - Val - Ala
c. Leu - Cys - Asp - Ile - Ala
d. Asp - Thr - Leu
On planet Zork, DNA has the same composition as on Earth. This means that the genetic code is still specified by sequences of the same four nucelotides (i.e, G,C,A and T). However, rather than 20 basic amino acids, there are 120. Predict the number of nucleotides in a Zorkian codon (i.e., the minimum number needed in order to specify all 120 amino acids).
a. 3
b. 4
c. 12
d. 100
e. 120
On planet Claire, there are 20 basic amino acids, but the DNA contains only two nucleotides (G and C) rather than four as on earth. What would be the smallest possible codon length needed to specify all 20 amino acids on Claire?
a. 2
b. 3
c. 4
d. 5
e. 6
If a DNA template strand 3' - CAAGTCTCC - 5' mutates to 3' - CACGTCTCC - 5', what kind of mutation has occurred? (Use a codon table)
a. silent mutation
b. missense mutation
c. nonsense mutation
d. frameshift mutation
For each of the following, choose the letter corresponding to the term which best describes it. Some terms will not be used, but none will be used more than once.
a. A site | b. aminoacyl-tRNA synthetase | c. deamination | d. DNA ligase | e. DNA polymerase | f. Down syndrome | g. helicase | h. methionine | i. P site | j. peptidyl transferase | k. promoter | l. redundancy | m. release factor | n. replication fork | o. ribose | p. ribosome | q. RNA primer | r. RNA polymerase | s. sickle-cell anemia | t. spliceosome | u. telomerase | v. thymine | w. topoisomerase | x. transcription | y. wobble | z. x-rays
1. Unwinds DNA double helix to initiate DNA replication
2. DNA polymerase adds to this to begin elongation
3. Joins Okazaki fragments
4. DNA-directed synthesis of RNA
5. RNA polymerase binds to this to initiate transcription
6. Start codon codes for this
7. Two or more codons code for same amino acid (e.g. UUU and UUC for phenylalanine)
8. Site holding the tRNA carrying the growing polypeptide chain
9. Complex of snRNPs and other proteins, used in intron splicing
10. Joins a specific amino acid to a tRNA
11. Peptide bond formation accomplished by this enzyme
12. Ability of one tRNA to recognize more than one mRNA codon
13. Site of translation
14. A cause of frameshift mutations
15. A cause of point mutations
16. Caused by a point mutation