Biology Test 3

In carnations, heterozygotes have pink flowers, whereas the two homozygotes have red flowers (RR) or white flowers (rr). When plants with pink flowers are crossed with plants with white flowers, what proportion of the offspring will have red flowers?

0%

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'.

The direction of synthesis of an RNA transcript is _____.

5' —> 3'

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

A gene from an organism can theoretically be expressed by any other organism.

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is

AAA.

Several black guinea pigs of the same genotype were mated and produced 29 black and 9 white offspring. What were the genotypes of the parents if black (B) is dominant to white (b)?

Bb x Bb

All of the following are directly involved in translation except

DNA

What enzyme joins Okazaki fragments?

DNA ligase

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?

DNA polymerase III

Use the following information to answer the next question. A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already. Where does tRNA #2 move to after this bonding of lysine to the polypeptide?

E site

In humans free earlobes are dominant over attached earlobes. What are the possible genotypes of the offspring from a cross between parents that are Ee and Ee.

EE, Ee, ee

The genotype of an individual is GgFf. The possible genotypes of the gametes produced by this individual are:

GF, Gf, gF, gf

What is the effect of a nonsense mutation in a gene?

It introduces a premature stop codon into the mRNA.

Which of the following statements about the DNA in one of your brain cells is true?

It is the same as the DNA in one of your heart cells.

Why might a point mutation in DNA make a difference in the level of protein's activity?

It might substitute an amino acid in the active site.

What is the function of reverse transcriptase in retroviruses?

It uses viral RNA as a template for DNA synthesis.

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?

No replication fork will be formed.

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?

Proto-oncogenes normally help regulate cell division.

A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?

The plants would develop the typical symptoms of TMV infection.

The figure represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?

UUC

Use the following list of choices for the following questions: I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes synthesizes short segments of RNA?

V

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

a deletion of two nucleotides

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in

a polypeptide missing an amino acid.

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

On this model of a tRNA molecule, identify each of the following:

a) 5′ and 3′ ends b) hydrogen bonds c) anticodon loop d) binding site for amino acid

Tumor-suppressor genes

can encode proteins that promote DNA repair or cell-cell adhesion.

A nonreciprocal crossover causes which of the following products?

deletion and duplication

The fact that plants can be cloned from somatic cells demonstrates that

differentiated cells retain all the genes of the zygote.

A frameshift mutation could result from

either an insertion or a deletion of a base.

In animals, embryonic stem cells differ from adult stem cells in that

embryonic stem cells are totipotent, and adult stem cells are pluripotent.

Gene Bama is activated when Ala binds to it. Ala represents the:

ligand

What is the source of the extra chromosome 21 in an individual with Down syndrome?

nondisjunction or translocation in either parent

In pansies, purple (P) is dominant to yellow (p). What is the phenotype of a Pp pansy?

purple

Which viruses have single-stranded RNA that acts as a template for DNA synthesis?

retroviruses

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

single-strand binding proteins

The leading and the lagging strands differ in that

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

Cell differentiation always involves

the production of tissue-specific proteins, such as muscle actin.

The host range of a virus is determined by

the proteins on its surface and that of the host.

BRCA1 and BRCA2 are considered to be tumor-suppressor genes because

their normal products participate in repair of DNA damage.

What is the function of DNA polymerase?

to add nucleotides to the 3' end of a growing DNA strand

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?

tortoiseshell females; black males

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this alteration called?

translocation

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

8%

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 growing strand.

What is meant by the description "antiparallel" regarding the strands that make up DNA?

The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

Who is credited with explaining the structure of the DNA double helix?

Watson and Crick

What is the reason that linked genes are inherited together?

They are located close together on the same chromosome.

Which of the following statements describes proto-oncogenes?

They can code for proteins associated with cell growth.

The anticodon of a particular tRNA molecule is

complementary to the corresponding mRNA codon.

In DNA, the two purines are ____________, and the two pyrimidines are ____________.

adenine and guanine...cytosine and thymine

Which of the following accounts for someone who has had a herpesvirus-mediated cold sore or genital sore getting flare-ups for the rest of his or her life?

copies of the herpesvirus genome permanently maintained in host nuclei

Which of the three types of viruses shown above would you expect to include a capsid(s)?

all three

When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate?

an assembled ribosome with a polypeptide attached to the tRNA in the P site

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

leading strands and Okazaki fragments.

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

males are hemizygous for the X chromosome.

DNA controls metabolism by directing cells to make specific enzymes and other proteins , via a process called:

gene expression

In colorectal cancer, several genes must be mutated in order to make a cell a cancer cell, supporting Knudsen's hypothesis. Which of the following kinds of genes would you expect to be mutated?

genes involved in control of the cell cycle

Which of the following characteristics, structures, or processes is common to both bacteria and viruses?

genetic material composed of nucleic acid

Which of the following can be effective in preventing the onset of viral infection in humans?

getting vaccinated

Gene Bama is activated when Ala binds to it. Binding represents the ____ stage of cell signaling.

reception

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

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 E

If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis?

1/4 of the gametes will be n + 1, 1/4 will be n - 1, and 1/2 will be n.

A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be

3' AAA-GAA-TAA-CAA 5'.

In which direction does the RNA polymerase move?

3' → 5' along the template strand

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'

The following is a map of four genes on a chromosome. Figure 15.1 Between which two genes would you expect the highest frequency of recombination?

A and G

Which of the following is characteristic of the lytic cycle?

A large number of phages are released at a time.

According to the signal hypothesis, ribosomes are directed to the ER membrane by...

By a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane

Recombination between linked genes comes about for what reason?

Crossovers between these genes result in chromosomal exchange.

A new DNA strand elongates only in the 5' to 3' direction because

DNA polymerase can only add nucleotides to the free 3' end.

Use the following list of choices for the following questions: I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes separates the DNA strands during replication?

I

Which of the enzymes covalently connects segments of DNA? Use the following list of choices for the following questions: I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase

III

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

It joins Okazaki fragments together.

Which of the following statements is true of linkage?

The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.

In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?

The entire template molecule is represented in the product.

Three genes at three loci are being mapped in a particular species. Each has two phenotypes, one of which is markedly different from the wild type. The unusual allele of the first gene is inherited with either of the others about 50% of the time. However, the unusual alleles of the other two genes are inherited together 14.4% of the time. Which of the following describes what is happening?

The first gene is assorting independently from the other two that are linked.

In peas, round seed (R) are dominant to wrinkled seeds (r) and yellow seeds (Y) are dominant to green seed (y). In the cross RrYY x rrYy, what is the probability of getting round, green peas?

Zero

The template strand of a given gene includes the sequence 3′-G C C A C G T A T C A G-5′. a) What is the sequence of the nontemplate strand? b) What is the mRNA sequence made?

a) nontemplate strand ~ 5'-C G G T G C A T A G T-3' B)

The enzyme that orchestrates the binding of a specific amino acid to transfer RNA is:

aminoacyl-tRNA synthase

Muscle cells differ from nerve cells mainly because they

express different genes.