Biochemistry Exam 2

How many pairs of autosomes does the human genome have?

22

In DNA replication, the new strand always grows in the _____ direction.

5 to 3

What statement about plasmids is FALSE?

A bacterial cell always has plasmids.

What statement about nucleosides is CORRECT?

A nucleotide is a nucleoside with a phosphate ester linked to the sugar.

What statement about the palindromic sequence is FALSE? -It is the DNA sequence that reads the same from right to left as it does from left to right. -A restriction enzyme recognizes any sequence as long as it is palindromic. -It contains a twofold axis of symmetry. -It is the specific sequence of four to eight base pairs. -A restriction enzyme hydrolyzes hydrogen bonds in this region.

A restriction enzyme recognizes any sequence as long as it is palindromic.

The base pair that would be found in RNA is:

A-U.

The first three bases of the six-base recognition cleavage site of HindIII are AAG. What is the complete sequence of this 6-bp site?

AAGCTT

Choose the point mutation. GTA-> ATC GGG >ATC AAA >TTT ATT >ATA CCT >TCC

ATT ATA

Each three-base codon encodes a specific:

Amino Acid

The enzyme that catalyzes the formation of a phosphodiester linkage at a break in a DNA strand is:

DNA ligase.

What enzyme catalyzes the step-by-step addition of deoxyribonucleotide units to a DNA strand on the basis of template DNA?

DNA polymerase

Codons that specify the same amino acid are termed: _________ codons.

Degenerate

Choose the feature of DNA structure that was NOT deduced by Watson and Crick from the DNA diffraction patterns.

Double-helical DNA can be supercoiled.

What is the nucleotide sequence on the DNA coding strand that yields the GUC codon for valine?

GAC

What DNA sequence contains a palindromic inverted repeat such as those recognized by restriction enzymes? (Note: Only one strand is shown.)

GCATATGC

How does the binding of oxygen to one subunit of hemoglobin influence the remaining subunits? -In the sequential model, binding of oxygen to one subunit converts the whole tetramer to the high-affinity conformation. -In the sequential model, binding of oxygen to one subunit does not influence the remaining subunits. -In the concerted model, binding of oxygen to one subunit converts the whole tetramer to the high-affinity conformation. -In the concerted model, binding of oxygen to one subunit does not influence the remaining subunits. -In the concerted model, binding of oxygen to one subunit directly influences the remaining subunits.

In the concerted model, binding of oxygen to one subunit converts the whole tetramer to the high-affinity conformation.

What is the difference between lytic and lysogenic pathways that λ phage uses for multiplying?

In the lysogenic pathway, viral DNA is integrated in the E. coli genome, while in the lytic pathway, phage DNA multiplies without insertion.

What is the functional role of the "distal histidine"?

It donates a hydrogen bond to the bound oxygen molecule to stabilize the complex between iron and oxygen.

What statement about polyacrylamide gels and agarose gels is FALSE? -Agarose gels are used to resolve mixtures of fragments as large as 20 kilobases. -Agarose gels are more porous than polyacrylamide gels. -Bands or spots of radioactive DNA in both of these gel types can be visualized by autoradiography. -Polyacrylamide gels are used to separate mixtures of larger fragments than agarose gels can separate. -These gels have a high resolving power.

Polyacrylamide gels are used to separate mixtures of larger fragments than agarose gels can separate.

How many chiral carbon atoms do ribose and deoxyribose contain in nucleic acids?

Ribose contains 4 chiral carbon atoms, whereas deoxyribose contains 3.

The MOST common type of DNA sequencing is the _____ method.

Sanger dideoxy

In bacterial mRNA, the initiating AUG codon is preceded several nucleotides away by a purine-rich sequence called the _____, which base-pairs with a complementary sequence in an rRNA.

Shine-Dalgarno sequence

A student separated some RNA from yeasts. What would be a result of dialyzing this sample against the buffer without Mg2+ and Ca2+?

Stem-loop structures in the RNA would be destabilized.

A _____ DNA molecule is more compact than its relaxed form.

Supercolied

What is the nucleotide sequence on the DNA template strand that yields the CUA codon for leucine?

TAG

What is the difference between the T form and R form of the hemoglobin molecule? -The T form of the hemoglobin molecule is unstable without 2,3-BPG. -The R form of the hemoglobin molecule is unstable. -The R form of the hemoglobin molecule has the oxygen-binding sites free of strain. -The T form of the hemoglobin molecule is not constrained by subunit-subunit interactions. -The R form of the hemoglobin molecule has a pocket in the center of the tetramer for 2,3-BPG.

The R form of the hemoglobin molecule has the oxygen-binding sites free of strain.

What statements concerning myoglobin is NOT CORRECT?

The heme group is bound to the globin chain by two disulfide bonds.

The base composition of the DNA includes 28% G and 26% A. How much T would be in the RNA synthesized from this DNA template?

The original data are not correct.

What is the Bohr effect?

The regulation of oxygen binding by hydrogen ions and carbon dioxide

What is NOT a feature of PCR?

The sequence of the target needs to be known so that complementary primers can be synthesized.

Why are Met and Trp codons often used to design DNA probes from amino acid sequences?

They are not degenerate and have single codons.

What advantage can be gained by splicing together portions of two different genes?

This technique allows the creation of proteins with unique characteristics and activities.

The temperature at which half of the DNA helical character is lost is referred to as: Th. TDNA. T0.5. T50. Tm.

Tm

What statement about DNA replication is INCORRECT? -DNA polymerases catalyze the formation of a phosphodiester linkage efficiently only if the base on the incoming deoxynucleoside triphosphate is complementary to the base on the template strand. -To begin synthesis, DNA polymerases require a primer with a free 5-OH group that is already bound to the template strand. -The reaction requires deoxynucleoside 5-triphosphates dATP, dGTP, dCTP, and TTP and a Mg2+ ion. -DNA polymerases build a phosphodiester bridge up in a reversible manner before pyrophosphate is hydrolyzed by pyrophosphatase. -Many DNA polymerases have a distinct nuclease activity that allows them to excise incorrect bases by themselves.

To begin synthesis, DNA polymerases require a primer with a free 5-OH group that is already bound to the template strand.

Homologous recombination is the process in which:

Two DNA molecules with a strong sequence similarity exchange segments.

The difference in RNA bases compared with DNA bases is that RNA contains:

U instead of T.

Under physiological conditions, most DNA is in the form of a _______ form helix.

Z

What are the common promoter regions found in eukaryotic genes?

a TATA box at about -25 and often a CAAT box at about -75

The probe used to isolate a gene from a genomic library is often:

a portion of the mRNA of the gene.

What component is strongly required by DNA polymerases but is NOT needed by RNA polymerase?

a primer

Due to what mechanism do many genes encode more than one protein?

alternative splicing

Which step is NOT included in the technique called Southern blotting? -exposure to a 32P-labeled DNA probe -hybridization of the probe with a restriction fragment having a complementary sequence -amplification of the restriction fragment-probe duplex -transfer of the mixture of restriction fragments into a membrane composed of nitrocellulose -visualization by autoradiography or fluorescence imaging

amplification of the restriction fragment-probe duplex

The process of DNA renaturation after melting is called:

annealing.

How can the helix diameter for DNA in the A form be described as compared to other DNA forms?

broadest

Which model better explains the cooperative binding of oxygen by hemoglobin?

combination of sequential and concerted models

What type of binding is indicated by a sigmoidal-shaped binding curve?

cooperative

As the partial pressure of carbon dioxide increases, the affinity of oxygen binding to hemoglobin:

decreases.

The nucleoside that is composed of a D-deoxyribose linked to a cytosine base is called:

deoxycytidine.

What is the technique on which the Watson-Crick model was based?

electron microscopy

What sequences in eukaryotes link together to form mRNA after splicing?

exons

A pattern of DNA fragments can serve as a _____ of a particular DNA molecule.

fingerprint

Thalassemia results:

from decreased production of one of the subunits of hemoglobin.

A noncoding region within a gene is known as a(n):

intron.

Although the right-handed double helix is the most well-known DNA structure, DNA can also form:

left-handed helices.

What group (or atom) of the nucleotide base is esterified to a phosphate group to bind that nucleotide to the next one? -N-1 in purines and N-9 in pyrimidines none N-9 in purines and N-1 in pyrimidines the 3-hydroxyl (3-OH) group the 5-hydroxyl (5-OH) group

none

The yeast artificial chromosomes (YACs) do NOT have a(n):

operon

Introns nearly always begin with GU and end with AG that is preceded by the _______.

pyrimidine-rich tract

Which molecules are used as a template in translation?

rRNA

Ribosomes are composed of:

rRNA and proteins.

What enzyme is capable of synthesizing DNA from an RNA template?

reverse transcriptase

What is NOT included in the PCR mixture?

reverse transcriptase

The DNA fragment was inserted into the specific plasmid. What do plasmid and the DNA fragment have in common?

same sticky ends

The Bohr effect influences the oxygen-binding curve by:

shifting the oxygen-binding curve to the right.

Choose the right temperature for each step of the PCR cycle (the cycles have to be in the right order).

strand separation - heating to 95°C; hybridization of primers - cooling to 54°C; DNA synthesis - heating to 72°C

What statement is CORRECT concerning the adaptor molecule tRNA? -tRNA contains a poly A tail at the 3 end. -tRNA is the largest RNA in the cell. -tRNA contains an anticodon sequence that serves as the template recognition site. -tRNA serves as a gene in some viruses. -The amino acid is attached to the 5 end of tRNA.

tRNA contains an anticodon sequence that serves as the template recognition site.

What can be used to add nucleotides to the 3 end of DNA?

terminal transferase

Oxygen binding at the coordination site causes:

the iron atom to move from outside the plane of the porphyrin into the plane.

Ti plasmids stand for:

tumor-inducing plasmids

The chemical forces that contribute to the stability of the DNA due to the base stacking present in the DNA helix are:

van der Waals interactions.

The normal adult hemoglobin A contains:

α1β1 and α2β2 dimers.

What is a structure of the hemoglobin molecule?

α2β2 tetramer

What bonds link bases to sugars in nucleotides?

β-glycosidic