bio 112 exam 4

A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have

T4 protein and T4 DNA

 Viruses use host cell to make

viral nucleic acids and viral proteins

 In trying to determine whether DNA or protein is the genetic material, Hershey and
Chase made use of which facts

 DNA contains phosphorus, whereas protein does not

During the Hershey and Chase experiment, the T2 phage

 injected 32P labeled DNA into cells

If the amount of guanine in a cell is 19 percent, what would you expect to be the
percentage of thymine in this cell?

31 percent

 What is the most current description of a gene?

A DNA sequence that is expressed to form a functional product: either RNA or polypeptide

 In analyzing the number of different bases in a DNA sample, what combinations would be consistent with the base-pairing rules?

 A+G = C+T

 In the polymerization of DNA, a phosphodiester bond is formed between a phosphate
group of the nucleotide being added and ______ of the last nucleotide in the polymer.

the 3’ OH

Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement

permits complementary base pairing

 What would be the consequence of having the two complementary DNA strands being held together by covalent bonds?

Covalent bonds are very strong bonds and it would be hard to break them and replicate the DNA strands

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

Meselson and Stahl

Semiconservative replication involves a template. What is the template?

One strand of the original DNA molecule

DNA is synthesized through a process known as

semiconservative replication

 List the correct order of the DNA replication steps

1. Hydrogen bonds between base pairs of antiparallel strands are broken.

2. 2. Single-stranded binding proteins attach to DNA strands.

3. 3. Primase binds to the site of origin.

4. 4. An RNA primer is created. 5 DNA polymerase binds to the template strand.

DNA contains the template needed to copy itself, but it has no catalytic activity in cells. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed?

DNA polymerase

What provides the energy for the polymerization reactions in DNA synthesis?

Deoxyribonucleotide triphosphate(dNTP)

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?

Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have multiple origins of replication

 During DNA replication, the enzyme ______ unwinds the DNA to create the replication bubble and the enzyme______ moves ahead of the replication fork to relieve the supercoiling of the DNA. 

helicase, topoisomerase

In E. coli, what is the function of DNA polymerase III?

Add nucleotides to the 3’ end of a growing DNA strand

 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

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

It joins Okazaki fragments together

_______help(s) to hold the DNA strands apart while they are being replicated 

single-strand DNA binding proteins

Eukaryotic telomeres replicate differently than the rest of the chromosome because of_ 

gaps left at the 5’ end of the lagging strand

The DNA of telomeres has been highly conserved throughout the evolution of eukaryotes. This most likely reflects ______

the critical function of telomeres

 What is a telomere?

The ends of linear chromosomes

. __________cell types is likely to demonstrate the lowest level of telomerase activity 

somatic cells

Telomere shortening is a problem in ___

only eukaryotic cells

What is gene expression?

Process of converting information in DNA into functioning molecules within the cells

The One-Gene, One-Polypeptide Hypothesis states that:

each gene is responsible for the synthesis of a single polypeptide chain

Which scientists are most closely associated with the experiments that led to the One- Gene, One-Polypeptide Hypothesis?

Beadle and tatum

Knockout mice have been genetically altered to knockout specific genes. How are these mice most often used in research?

To determine the role of proteins coded for by those genes that are knocked out

The statement “DNA → RNA → Proteins” is known as

The central dogma of molecular biology 

____is not directly synthesized from a DNA template

Amino acids

 In the process of transcription, __ is synthesized

RNA

 In Eukaryotes, the process of ______ which involves making mRNA from a gene sequence occurs in the __, and the process of ______ which involves making proteins from the mRNA occurs in the ____.

transcription, nucleus, translation, cytosplasm

 What is the name of the enzyme present in some retroviruses that synthesizes DNA
from RNA?

Reverse transcriptase

___ is to transcription as __ is to translation.

RNA polymerase, a ribsome

Given the following DNA template -TTTTTTT, what bases would you find in a
complementary RNA strand and where would they be synthesized?

A-A-A-A-A-A-A;nucleus

Suppose that you have the following DNA template:3’ ATG-GGC-AAT-CGC 5’. What
would be the sequence of the mRNA generated from the above DNA?

UAC-CCG-UUA-GCG 3’

 Which codon typically serves as the start signal for translation?

AUG

Stop codons in the genetic code: ___

UAA,UAG,UGA

What does it mean when we say the genetic code is unambiguous?

The same codon always specifies the same amino acid

What does it mean to say that the genetic code has redundancy?

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

. How many bases are required to code for a single amino acid?

3

The genetic code is considered nearly universal because

all codons specify the same amino acids in nearly all organisms

If each codon consisted of two nucleotides what would be the maximum amount of
amino acids that could be encoded by all combinations of the nucleotides in the codon?

16

The mutation resulting in sickle cell disease changes one base pair of DNA so that a
codon now codes for a different amino acid, making it an example of a ______

missense mutation

 A mutation that results in premature termination of translation ______

nonsense

 What is silent mutation?

A change in DNA sequence that does not alter the resulting amino acid

 A frameshift mutation could result from ______

either an insertion or deletion of a base

 In E. coli (bacteria), if RNA polymerase is missing ______, then transcription initiation would not occur at the appropriate initiation sites.

sigma

You want to engineer a eukaryotic gene into a bacterial colony so the bacteria express the gene. What must be included in addition to the coding exons of the gene?

A bacterial promoter sequence

______is central to the initiation of transcription in bacteria.

binding of sigma to the promoter region

Termination of transcription in bacteria occurs when______

a hairpin secondary structure forms in the RNA transcript, and it separates from the RNA polymerase

 Once transcription begins, what happens to the σ (sigma) factor in the bacterial
Holoenzyme?

It dissociates after initiating RNA synthesis

__________occurs in prokaryotes but NOT in eukaryotes

concurrent transcription and translation

Ribosomes can attach to prokaryotic messenger RNA ___

before transcription is complete

What is the primary purpose of RNA splicing?

To remove introns and join exons into a continuous sequence

 Introns are best described as:

noncoding regions removed from pre-mRNA

The adapter molecule used in translation is

transfer RNA(tRNA)

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that____

the rules for base pairing between the third base of a codon and tRNA are flexible

The anticodon of a particular tRNA molecule is ______

complementary to the corresponding mRNA codon

The ribosome binding site of prokaryotes is also known as the

Shine-Dalgarno sequence

 During elongation, which site in the ribosome represents the location where a codon is being read?

A site

 Once a peptide bond has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next?

Translocation

_____ if missing, would usually prevent translation from starting in eukaryotes

5’cap and AUG codon

Translation requires ______________

mRNA, tRNA, and rRNA

 What type of chromosomal mutation occurs when a segment of a chromosome is
inserted into another non-homologous chromosome?

translocation

Which chromosomal mutation results in the reversal of a segment within the same
Chromosome?

inversion

 A mutation where a chromosome segment is copied and added to the same
chromosome is called:

duplication