Bio Final (4)
Which one of the following structures, if missing, would usually prevent translation from starting?
AUG codon
Which of the following molecular structures contain codons?
mRNA
Cinnabar eye color 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 F 1 males will have cinnabar eyes?
100%
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?
12%
Thymine makes up 26% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be guanine?
24%
Which of the following sequences of nucleotides are possible in the template strand of DNA that would code for the polypeptide sequence Phe-Leu-Ile-Val? (q 32)
3′-AAA-GAA-TAA-CAA-5′
Refer to the figure. Which of the triplets below is a possible anticodon for a tRNA that transports proline to a ribosome? (q 50)
3′-GGC-5′
Rank the following one-base point mutations with respect to their likelihood of affecting the structure of the corresponding polypeptide (from most likely to least likely). 1- insertion mutation deep within an intron 2- substitution mutation at the third position of a codon in an exon 3- substitution mutation at the second position of a codon in an exon 4- deletion mutation within the first exon of the gene
4,3,2,1
Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?
47, trisomy 21
At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T ( T) of the template. Which of the following represents the primer sequence?
5' A C G U U A G G 3'
Using Figure 17.6, identify a 5′ → 3′ sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys. (q 45)
5-CTTCGGGAA-3
Referring to the figure, what bases will be added to the primer as DNA replication proceeds?
5′ A, G, A, C, G, A, C 3′
E = exon and I = intron 5′-UTR E 1 I 1 E 2 I 2 E 3 I 3 E 4 UTR-3′ Which components of the previous molecule will also be found in mRNA in the cytosol?
5′-UTR E 1 E 2 E 3 E 4 UTR-3′
In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?
A + G = C + T
Which of the following processes occurs in eukaryotic gene expression?
A cap is added to the 5′ end of the mRNA.
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true?
A gene from an organism can theoretically be expressed by any other organism
During the elongation phase of translation, which site in the ribosome represents the location where a codon is being read?
A site
Which of the following effects might be caused by reduced or very little active telomerase activity?
Cells age and begin to lose function
Hershey and Chase set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell?
DNA
Which component is not directly involved in translation?
DNA
Which of the following facts did Hershey and Chase make use of in trying to determine whether DNA or protein is the genetic material?
DNA contains phosphorus, whereas protein does not
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?
DNA in both daughter cells would be radioactive
A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
DNA ligase
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
DNA polymerase can join new nucleotides only to the 3′ end of a pre-existing strand, and the strands are antiparallel
Which of the following investigators was (were) responsible for the discovery that in DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine?
Erwin Chargaff
Which of the following is not true of RNA processing?
Exons are cut out before mRNA leaves the nucleus
Which of the following molecular characteristics cause histones to bind tightly to DNA?
Histones are positively charged, and DNA is negatively charged.
Which of the following processes correctly describes alternative RNA splicing?
It can allow the production of proteins of different sizes and functions from a single mRNA
How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?
It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.
hich of the following is not true of a codon?
It extends from one end of a tRNA molecule
Which of the following statements correctly describes the effect a nonsense mutation would have on a gene?
It introduces a premature stop codon into the mRNA.
Which of the following statements accurately describes the structure of a eukaryotic chromosome?
It is a single linear molecule of double-stranded DNA plus proteins
Which of the following statements correctly describes a ribozyme?
It is an RNA with catalytic activity
Which of the following statements best describes the significance of the TATA box in the promoters of eukaryotes?
It is the recognition site for the binding of a specific transcription factor
Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine, and cytosine forms hydrogen bonds with guanine. What is the significance of the structural arrangement?
It permits complementary base pairing
Which of the following properties is associated with a protein that will be secreted from a eukaryotic cell?
Its signal sequence must target it to the ER, after which it goes to the Golgi
Why are males more often affected by sex-linked traits than females?
Males are hemizygous for the X chromosome
Which of the following statements correctly describes the meaning of the chromosome theory of inheritance as expressed in the early 20th century?
Mendelian genes are at specific loci on the chromosome and, in turn, segregate during meiosis
Once researchers identified DNA as the molecule responsible for transmitting heritable traits, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. Which of the following statements correctly describes the mechanism of information transfer in eukaryotes that accomplishes this task?
Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.
What amino acid sequence will be generated, based on the following mRNA codon sequence?5′-AUG-UCU-UCG-UUA-UCC-UUG-3′
Met-Ser-Ser-Leu-Ser-Leu
Which of the following statements is generally true of aneuploidies in newborns?
Monosomy X is the only viable monosomy known to occur in humans
The genetic code is redundant. What is meant by this statement?
More than one codon can specify the addition of the same amino acid.
In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?
No replication fork will be formed
A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?
One of the gametes in the mother most likely underwent nondisjunction during meiosis.
Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their 20s. How likely is it for a woman to have this condition?
One-half of the daughters of an affected father and a carrier mother could have this condition
Which of the following statements accurately describes the differences between DNA replication in prokaryotes and DNA replication in eukaryotes?
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many
Which of the following processes occurs during transcription?
RNA is synthesized
What is meant by the description "antiparallel" regarding the two strands that make up the DNA double helix?
The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.
The tRNA shown in the figure has its 3′ end projecting beyond its 5′ end. Which of the following processes will occur at this 3′ end?
The amino acid binds covalently.
In a healthy eukaryotic cell, the rate of DNA repair is typically equal to the rate of DNA mutation. When the rate of repair lags behind the rate of mutation, what is a possible fate of the cell?
The cell can be transformed into a cancerous cell
Which of the following statements regarding gene linkage is correct?
The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them
Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight, and mutations to the DNA in their skin cells are left uncorrected. Why are the mutations not corrected in individuals with this disorder?
The disorder causes cells to be unable to repair thymine dimers
When Thomas Hunt Morgan crossed his red-eyed F 1 generation flies to each other, the F 2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?
The gene involved is located on the X chromosome.
Which of the following statements correctly describes the difference between ATP and the nucleotides used during DNA synthesis?
The nucleotides have the sugar deoxyribose; ATP has the sugar ribose
During meiosis, a defect occurs in a cell that results in the failure of spindle microtubules binding at the kinetochores. Which of the following statements describes the most likely result of such a defect?
The resulting cells will not receive the correct number of chromosomes in the gametes, a condition known as aneuploidy
Which of the following statements correctly describes the reason that closely linked genes are typically inherited together?
They are located close together on the same chromosome
Which of the following is an example of monosomy in humans?
Turner syndrome
A single base substitution mutation is likely to have a less deleterious effect when the base change exhibits which of the following results?
a codon that specifies the same amino acid as the original codon
The SRY gene is best described as ________.
a gene present on the Y chromosome that triggers male development
Which of the following mutations would be most likely to have a harmful effect on an organism?
a single nucleotide insertion downstream of, and close to, the start of the coding sequence
Post-translational modifications of proteins may include which of the following processes?
addition of carbohydrates to form a glycoprotein
Which of the following individuals will inherit an X-linked allele from a man who carries it?
all of his daughters
The anticodon of a particular tRNA molecule is
complementary to the corresponding mRNA codon
The elongation of the leading strand during DNA synthesis
depends on the action of DNA polymerase
In Drosophila melanogaster, vestigial wings are determined by a recessive allele of a gene that is linked to a gene with a recessive allele that determines black body color. T. H. Morgan crossed black-bodied, normal-winged females and gray-bodied, vestigial-winged males. The F 1 were all gray bodied, normal winged. The F 1 females were crossed to homozygous recessive males to produce testcross progeny. Morgan calculated the map distance to be 17 map units. Which of the following information is correct about the testcross progeny?
gray-bodied, normal-winged flies plus black-bodied, vestigial-winged flies = 17% of the total
In a nucleosome, the DNA is wrapped around
histones
What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure? (q 34)
hydrogen bonding between base pairs
Which of the following molecules are required for the process of translation?
mRNA, tRNA, and rRNA
In E. coli, to repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
nuclease, DNA polymerase, DNA ligase
Which of the following lists represents the order of increasingly higher levels of organization of chromatin?
nucleosome, 30-nm chromatin fiber, looped domain
E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?
one low-density and one intermediate-density band
Semiconservative replication involves a template. What is the template?
one strand of the DNA molecule
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information. Which of the following characteristics of DNA is responsible for this?
sequence of bases
In eukaryotic cells, transcription cannot begin until
several transcription factors have bound to the promoter
Which of the following types of molecules help to hold the DNA strands apart while they are being replicated?
single-strand DNA binding proteins
In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the polymer?
the 3' OH
How does the primary transcript in the nucleus of a eukaryotic cell compare to the functional mRNA?
the primary transcript is larger than the mRNA
In cats, black fur color is determined by an X-linked allele; the other allele at this locus determines orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?
tortoiseshell females; black males
Which of the following processes occurs in prokaryotes but not in eukaryotes?
transcription and translation occur simultaneously
One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this type of chromosomal alteration called?
translocation
Sex determination in mammals is due to the SRY gene found on the Y chromosome. Which of the following situations could allow a person with an XX karyotype to develop a male phenotype?
translocation of SRY to an X chromosome
