Biology Lecture Exam 5

According to the central dogma, what is the intermediate molecule involved in the flow of information that should go in the blank? DNA --> ____ --> Proteins

mRNA

Which of the following molecules are requires for this process of translation?

mRNA, tRNA, and rRNA

Semiconservative replication involves a template. What is the template?

one strand of the DNA molecule

Which of the following dipeptides will form from 5'-CCG-ACG-3'? tRNA Anticodon - Amino Acid GGC - Proline CGU - Alanine UGC - Threonine CCG - Glycine ACG - Cysteine CGG - Alanine

proline-theronine

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 organisms 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

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

AAA

Which one of the following structures, if missing, would usually prevent translation from starting? 1. Exon 2. 5' cap 3. Poly-A tail 4. AUG codon

AUG codon

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to radioactively label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogen atoms. Thus, labeling the nitrogen atoms would provide a stronger signal than labeling the phosphate. Why won't this experiment work?

Amino acids (and this proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins

A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in the figure would you expect if the DNA was replicated in a conservative manner?

B

Codons are three-base sequences in mRNA that specify the addition of a single amino acid to the growing protein chain during translation. How do eukaryotic codons and prokaryotic codons compare?

Codons are a nearly universal language among all organisms

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" (radioactive) nitrogen (13N) and then transferred them to a medium containing 14N (non-radiactive). Which of the results in the figure would be expected after one round of DNA replication in the presence of 14N?

D

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 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

Why does a new DNA strand elongate only in the 5' to 3' direction during DNA replication?

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

In DNA replication, the resulting daughter molecules contain one stand of the original parental DNA and one new strand. What is the explanation for this phenomenon?

DNA replication is semiconservative

Which of the following statements describes the process of transformation in bacteria?

External DNA is taken into a cell, becoming part of the cell's genome

Which of the following statements correctly describes the structure of chromatin?

Heterochromatin is highly condensed, whereas euchromatin is less compact

Which of the following molecular characteristics cause histones to bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged

What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure?

Hydrogen bonding between base pairs

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

It joins Okazaki fragments together

Who performed classic experiments that supported the semiconservative model of DNA replication?

Meselson and Stahl

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 5'-AUG-UCU-UCG-UUA-UCC-UUG-3'?

Met-Ser-Ser-Leu-Ser-Leu

In this transformation experiments, what phenomenon did Griffith observe?

Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form

The genetic code is redundant. What is meant by this statement?

More than one codon can specify the addition of the same amino acid

Which of the following list represents the order of increasingly higher levels of organization of chromatin?

Nucleosome, 30-nm chromatin fiber, looped domain

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

What is the function of the enzyme topoisomerase in DNA replication?

Relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix

After the first replication was oberserved in their experiments testing the nature of DNA replication Meselson and Stahl could be confident of which of the following conclusions?

Replication is not conservative

Which of the following types of molecules help to hold the DNA strands apart while they are being replicated?

Single-strand DNA binding proteins

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

If a cell were unable to product histone proteins, which of the following results would be a likely effect on the cell?

The cell's DNA could not be packed into its nucleus

Which of the following statements correctly describes the difference between the leading stand and the lagging stands in DNA replication?

The leading strand is synthesized continuously in the 5' -> 3' direction, while the lagging strand is synthesized discontinuously in the 5' -> 3' direction

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA during DNA replication?

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

In bacteria, there are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. Which of the following statements explains this fact?

The small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

Which of the following processes is the first event to take place in translation in eukaryotes?

The small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

Thymine makes up 28% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be guanine?

22%

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?

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?

3'-GGC-5'

Which of the following dipeptides will form from 5'-CCG-ACG-3'? tRNA Anticodon - Amino Acid GGC - Proline CGU - Alanine UGC - Threonine CCG - Glycine ACG - Cysteine CGG - Alanine

3'-GGC-5'

A particular triplet of bases in the template strand of DNA is 5'-AGT-3'. What would be the corresponding codon for the mRNA that is transcribed.

3'-UCA-5'

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 staring at the *T* of the template. Which of the following represents the primer sequence?

5' A C G U U A G G 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'

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

5'-UUC-3'

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%

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on the specificity in that...

Binding of the anticodon to the codon and the attachment of amino acids to tRNAs