BIO Exam 4 HW

The eukaryotic transcription initiation complex is (check all that apply)

-transcription of virtually all genes transcribed by RNA pol II requiring the same suite of general factors. -interactive with activators through DNA looping. -a basal factor associated with RNA pol II after positioning RNA pol II at the start site.

Coloration in the peppered moth (Biston betularia) is determined by a single gene with two alleles showing complete dominance. Dark moths are homozygous dominant or heterozygous for the gene, light moths are homozygous recessive. In a sample of 100 moths, you determine that 64 of the moths are dark. According to the Hardy-Weinberg rule, the expected frequency of the dominant allele is ___.

0.4

Antigens on red blood cells are hereditary traits that allow blood to be typed in different ways. One system is based on a gene with two alleles, M and N. If the frequency of the M allele in a population is 0.4, then according to the Hardy-Weinberg rule, the expected frequency of the heterozygous MN genotype is ___.

0.48

For a gene with two alternative alleles, A (with a frequency of p) and B (with a frequency of q), the term in the algebraic form of the Hardy-Weinberg equilibrium for the heterozygote genotype frequency is

2pq.

DNA replication always proceeds by adding new bases to the _______ end of an existing strand.

3'

The synthesis of a growing strand of DNA is carried out by adding nucleotides to the ___ end of an existing strand.

3'

Nucleotides have a phosphate group attached at the ___ carbon atom of the sugar.

5'

What is the difference between a gene that is derepressed and one that is induced?

A gene that is derepressed is turned on because a repressor protein is not bound without its cofactor. By comparison, a gene that is induced is turned on because an inducer molecule prevents binding of the repressor.

What would happen if snRNPs did not recognize the branch point within an intron?

A lariat would not form.

A scientist makes three artificial mRNA strands: (x) 5' AAAUUUAAAUUUAAAUUUAAAUUUAAA 3'(y) 5' UUUCCCUUUCCCUUUCCCUUUCCCUUU 3'(z) 5' AUAUAUAUAUAUAUAUAUAUAUAUAU 3'When he analyzes the polypeptides produced, he finds that:x produces a polypeptide that is 50% phenylalanine and 50%lysine.y produces a polypeptide that is 50% phenylalanine and 50% proline.z produces a polypeptide that is 50% isoleucine and 50% tyrosine.Based on these results only, the best conclusion to make is that

AAA codes for lysine

Some flowering plants cannot self-pollinate which increases their tendency to mate with phenotypically different mates, a process called disassortative mating. What effect would this have on a population in Hardy-Weinberg equilibrium?

An increase in heterozygotes would be observed.

The "one-gene/one-enzyme" hypothesis was proposed by

Beadle and Tatum.

Although 61 different codons code for amino acids, cells contain fewer than 61 different tRNAs. Why?

Because the 5' base on the tRNA anticodon has some flexibility (wobble); thus, some tRNA anticodons can pair with more than one mRNA codon.

Suppose a new species of bacterium is discovered. It contains a form of DNA pol III that can add new nucleotides to either the 5' end or the 3' end of an existing strand. All other properties of the enzyme remain unchanged. How would DNA replication in these bacteria differ from normal replication?

Both new strands could be synthesized continuously like the leading strand.

During replication, which enzyme unwinds the DNA double helix?

DNA helicase

You are studying the effects of specific transcription factors on the activation of gene expression. You notice that one particular transcription factor binds far away from the promoter of its target gene. What can explain this?

DNA looping brings the transcription factor closer to the promoter and initiates gene transcription.

During DNA replication, which enzyme removes the RNA primers and then fills in the gap?

DNA pol I

Avery and his coworkers showed that the agent responsible for changing nonvirulent bacteria into virulent bacteria was

DNA.

The Central Dogma of biology can be stated as

DNA→ RNA→ proteins.

During translation, uncharged tRNA molecules leave the ribosome from the _________ site.

E

Who originally discovered the process of bacterial transformation?

Griffith

Genotypes are said to be in ___________ equilibrium if there is random mating and no other forces tend to alter the proportions of alleles from one generation to the next.

Hardy-Weinberg

Eukaryotic and prokaryotic organisms differ in how they process genetic information. Which statements best explain one of these differences?

In prokaryotes, translation of the mRNA begins before transcription is complete. In eukaryotes, transcription and modification of the mRNA is completed before translation begins.

____ would produce the smallest evolutionary change in a given period of time in a population of birds.

Mutation

During DNA replication, DNA pol III synthesizes the lagging strand in segments, called

Okazaki fragments.

You decide to repeat the Meselson-Stahl experiment, except this time you plan to grow the E. coli cells on light 14N medium for many generations and then transfer them to heavy 15N medium and allow them to grow for 2 additional generations (2 rounds of DNA replication). If the semiconservative model of DNA replication is correct, what is the expected distribution of DNA in the density gradient after two rounds of replication?

One band of intermediate density and one band of heavy density.

Ribosomes are complex aggregates of

RNA and proteins.

During translation in prokaryotes, formation of the initiation complex requires all of the following except

RNA polymerase.

____ would keep a population in Hardy-Weinberg equilibrium.

Random mating

The TFIID complex is formed by

TATA-binding protein TBP and TAFs.

Many factors bind around the core promoter to form the eukaryotic initation complex, but the most important one is ______, which directly binds the TATA box.

TFIID

In the graph above, which baby characteristics would explain the percent infant mortality curve and any subsequent effects on fitness?

The baby needs to be large enough to survive after birth, but small enough for a safe delivery.

Female cardinals select male mates in part based on their bright red color. What effect would this have on a cardinal population that was in Hardy-Weinberg equilibrium?

The frequency of red alleles would be greater than those predicted by Hardy-Weinberg equilibrium.

How would a large chromosomal inversion affect the expression of a gene if the gene is located between the two break points but no breaks occur within the gene?

The inversion would probably have no effect on gene expression.

If a strain of bacteria had a mutation that blocked expression of the lac repressor, what would you expect as a result?

The mutant strain would waste energy producing enzymes in the absence of lactose.

You are studying regulation of a prokaryotic operon. Experiments show that expression of the operon is increased when levels of biosynthetic product from that pathway are low. Based on this information, what is a likely mode of regulation?

The product binds a repressor, allowing it to bind the operator.

Which statement about the Hershey-Chase experiment is false?

The virus-infected bacteria contained radioactive sulfur.

A population of lizards lives in a rocky area next to a desert. Some lizards are light colored and blend into the sand. Others are dark and blend into the rocks. What may happen to this population of lizards over time?

They may evolve into two separate species as a result of disruptive selection.

The double helix model of DNA structure was proposed by

Watson and Crick.

In eukaryotes, specific transcription factors have two distinct domains:

a DNA-binding domain and an activation domain.

The observation that most pureblood Native Americans have type O blood is best explained by _____

a founder effect.

Moths that can evade a bat's echolocation have _____ that increase their likelihood of survival and reproduction.

adaptations

Natural selection for a certain phenotype will affect the _____ .

allele frequency of a population

Elucidation of the histone code might

allow us to turn specific genes on or off.

What is required for formation of the transcription initiation complex in eukaryotes?

binding of a transcription factor to the TATA box, followed by recruitment of additional transcription factors and recruitment of RNA polymerase II

A restriction in genetic variability caused by a drastic reduction in population size is called a

bottleneck effect.

During translation, the nucleotides that make up the mRNA are read in groups of three. These groups are called

codons.

Because the two strands of a DNA molecule are ________ to each other, either one can be used as a template to reconstruct the other.

complementary

DNA methylation is the only known natural modification of DNA. It affects

cytosine bases.

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder. Patients with XP exhibit a cellular hypersensitivity to ultraviolet (UV) radiation, a high incidence of skin cancer and premature aging. Based on these clinical characteristics, what is the most likely cause for this disease?

defects in DNA repair

In early ancestors of the modern giraffe, longer necks allowed animals to reach higher tree branches as food. This would lead to ____ in the ancestral giraffe population.

directional selection

The lagging strand is replicated with a series of Okazaki fragments and that is why its synthesis is considered to be

discontinuous.

Although the specific mechanism of RNA interference has not been fully defined, it involves

double stranded RNA interference with mRNA.

Sometimes, one gene pair will interfere with the expression of a second gene pair in an interaction called _______.

epistasis

Darwin proposed that natural selection occurs in an environment by

favoring heritable features that make the organism better suited to survive and reproduce.

The several hundred species of picture-winged fruit flies of the Hawaiian Islands are genetically very similar, yet they all differ markedly from their ancestral population in Asia. This is probably an example of _____

founder effect.

A defining characteristic of eukaryotic organisms is that they

have their transcription occurring in the nucleus and translation in the cytoplasm.

Two parents who do not have sickle cell anemia have a child that has the disease. The parents are both:

heterozygous for the sickle cell allele.

One of the DNA-binding motifs in many eukaryotic organisms that contains a nearly identical sequence of 60 amino acids is known as the

homeodomain.

In DNA, complementary nitrogen bases are held together by

hydrogen bonds.

You are asked to participate in a clinical trial for a new drug that can activate telomerase. Which of the following is a likely risk of such a drug?

increased vulnerability to cancer

The lactose analog isopropyl-beta-D-thio-galactoside (IPTG) is often used to regulate gene expression systems in bacteria. IPTG does not act as a substrate for beta-galactosidase, but can bind to, and inactivate, the repressor. In this case, IPTG serves as a(n)

inducer.

Avery, MacLeod, and McCarty's experiments revealed that the transforming principle had all of the following properties except

its activity was destroyed by treatment with proteases.

The proteins necessary for the use of lactose in E. coli are collectively called the

lac operon.

In eukaryotes, the 3' poly-A tail is attached to

mRNA.

Vertebrate cells possess a protein that binds to clusters of 5-methylcytosine and ensures the gene will stay in the "off" position. This control of gene regulation is a result of

methylation.

In Griffith's experiments,

mice infected with heat-killed virulent bacteria and live nonvirulent bacteria developed pneumonia and died.

Animals that select mates that are phenotypically similar will have _____ when compared with Hardy-Weinberg predictions.

more homozygotes.

In some organisms, the primary function of a gene in a cell is to participate in regulating the body as a whole rather than responding to the cell's immediate environment. These organisms would be

multicellular.

An insect population that becomes resistant to a commonly used insecticide is an example of _____.

natural selection

Histones that are tightly wound by DNA and are the basic unit of chromatin are called

nucleosomes.

An island is on the migration route of sea birds. This island also has abundant tree nesting birds that live on the island permanently and are not found on any other island. The tree nesting birds are more likely than the sea birds to be in Hardy-Weinberg equilibrium because:

of high immigration in the sea bird population.

The location of translation in prokaryotic cells is

on ribosomes.

A cluster of functionally-related genes that are regulated together and encoded into a single mRNA molecule is called a(n)

operon.

When a polypeptide is being assembled, the bond that forms between a newly added amino acid and the previous amino acid in the chain is a _________ bond.

peptide

The chemical bond connecting one nucleotide with the next along one strand of a DNA molecule is called a

phosphodiester bond.

Which enzyme adds new nucleotides to the end of a growing strand?

polymerase

You are working to identify enhancer regions of a particular gene. The best place to look is

primarily upstream of the promoter, possibly some distance away.

In eukaryotes, each type of RNA polymerase recognizes a different

promoter

DNA affects the traits of an organism by providing the instructions for synthesizing _______.

proteins

In multicellular organisms, the mechanism most directly responsible for directing development and maintaining homeostasis is gene

regulation.

Codons that serve as "stop" signals for translation are recognized by

release factors.

The p300/CBP (CREB-binding protein) proteins are histone acetyltransferases that help regulate the transcription of many genes. Based on this information you can conclude that these proteins

remodel chromatin.

The site where the two original DNA strands separate and active replication occurs is called the

replication fork.

After DNA replication is complete, each strand of the original molecule is bound to a new complementary strand. This process is known as

semiconservative replication.

During the splicing reaction, the intron-exon junctions are recognized by

snRNPs.

During transcription of mRNA in eukaryotes, some sequences are cut out of the primary transcript and the remaining sequences are joined together. This processing of mRNA is called _________.

splicing

The midrange of an array of phenotypes is favored in ____.

stabilizing selection

In DNA, a purine must always pair with a pyrimidine and vice versa in order to ensure that

the distance between the two phosphodiester backbones remains constant.

For a gene with two alternative alleles, B and b, the term q2 in the Hardy-Weinberg equation represents

the frequency of the bb genotype.

The A, P, and E sites are progressively occupied by amino acids being assembled into a polypeptide. These sites are part of

the large ribosomal subunit.

In some instances environmental change causes a situation where one phenotype is favored for a period of time, and then a different phenotype is favored. This oscillating selection causes

the maintenance of genetic variation in the population.

Eukaryotes have ____ type(s) of RNA polymerase.

three

The genetic code uses _________ nucleotide(s) to specify one amino acid.

three

Gene expression involves two phases, ___________ and translation.

transcription

As a microbiologist you have been asked to investigate the regulation of a novel gene in a bacterial species. Given what is known about bacteria, the logical place to begin your investigation is

transcriptional regulation.

Ribosome movement along the mRNA is called

translocation

When E. coli cells produce the amino acid tryptophan, a cluster of five genes is transcribed together. This cluster of genes is referred to as the

trp operon.

You are studying the function of a recently identified gene in C. elegans. You perform genetic screens for several months in an attempt to isolate loss-of-function gene mutations, but your efforts are unsuccessful. Your advisor suggests you try another approach to eliminate gene function. The best technique to accomplish this goal would be

use RNA interference to prevent mRNA translation.

Eukaryotic organisms speed up the process of DNA replication by

using multiple origins of replication on each chromosome.