Genomic Biology

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In eukaryotes, during S-phase of the cell cycle, the DNA of all chromosomes is replicated using mechanisms relatively similar to those of bacteria. What in addition to the new DNA strands must be made during S-phase to permit the synthesis of the new sister chromatids?

two new strands of DNA for each chromosome, and enough histone 2A, 2B, 3, and 4 to double the number of nucleosomes that existed before replication

The study of which genetic disease led Garrod to propose that there is a special relationship between genes and enzymes?

alkaptonuria

The one-gene, one enzyme hypothesis was proposed by ___ in 1942.

Beadle and Tatum

The test organism that helped researchers elucidate the one-gene; one enzyme hypothesis was

Neurospora crassa

Mutant strains of a bacterium that are unable to grow on a minimal medium are

auxotrophic

A methionine auxotroph

can grow on minimal medium supplemented with methionine

The frequency of PKU in Caucasian populations is approximately

1/10,000

In PKU, the absence of enzyme activity effects which step in the phenylalanine metabolism pathway?

conversion of phenylalanine to tyrosine

The Guthrie test for PKU requires the use of which microorganism?

Bacillus subtilis

Phenylketonurics are advised to avoid the artificial sweetener Nutrasweet because it contains

phenylalanine

The normal version of the mutant gene responsible for albinism in humans encodes an enzyme that converts

DOPA to melanin

The mutant gene responsible for PKU is located on

chromosome 12

Which disease is caused by a mutation in a gene located on the X chromosome?

Lesch-Nyhan syndrome

The most severe form of Lesch-Nyhan syndrome affects

males only

Which of the following is characterized as a lysosomal storage disease?

Tay-Sachs disease

The mutant gene responsible for Tay Sachs disease is located on

chromosome 15

The mutation responsible for the sickle cell disease affects ___ in the hemoglobin gene.

a single base pair

A person who was homozygous for the recessive mutant allele h, and was IAi at the ABO locus, would have which blood type?

O

Which gene is responsible for the expression of blood group antigens on the surface of red blood cells?

H

A child born to a man and a woman who are both carriers of the mutant allele responsible for cystic fibrosis has a ___ chance of having the disease.

25%

The frequency of cystic fibrosis in Caucasian populations is ___ the frequency of the disease in people of African descent.

greater than

A heterozygote with a mutant allele for phenylalanine hydroxylase would have which phenotype?

none of the above

Genetic counselors determine the risk of a genetic disease in a family by first performing

pedigree analysis

Cystic fibrosis is caused by a mutation in the gene that encodes which enzyme?

CFTR protein

In people who do not have Tay-Sachs disease, the hexA gene encodes an enzyme that

cleaves acetylgalactosamine from gangliosides

Sickle-cell disease is caused by a mutation that affects which type of cell?

red blood cells

Among Caucasians, the most common lethal autosomal recessive disease is

cystic fibrosis

A bacteria that is a histidine auxotroph should be grown on a medium that

contains histidine

The mutation responsible for cystic fibrosis occurs in a gene that is located on which chromosome?

7

The genotype for a person with type O blood is

i/i

A person with sickle-cell trait has ________ at the beta-globin gene locus.

one wild-type and one mutant allele

Two people who are considering having children see a genetic counselor, who determines that they are both heterozygous for a deleterious allele. The counselor advises them that their risk of producing a child with this genetic disease is

1/4

The following is a representation of a metabolic pathway involving genes for enzymes A, B, C, and D:
A -----> B -----> C -----> D -----> product
A mutation in the "B" gene would result in an accumulation of which gene product?

A only

A person with the genotype IA/i H/h would have which blood type?

A

Tay-Sachs disease is most prevalent in which population?

Ashkenazi Jews of central European descent

In Caucasian populations, approximately 1 out of every ________ people is a carrier for cystic fibrosis

20

The Nobel Prize-winning researchers who are credited with determining that one enzyme is produced from one gene are

Beadle and Tatum

A person with PKU

accumulates phenylalanine in his or her tissues.

Individuals who are homozygous for the h allele have which blood type?

O

In 1902, Archibald Garrod and his colleague William Bateson performed experiments which indicated that

there is a link between genes and enzymes.

Lesch-Nyhan syndrome is caused by a mutation in a gene located on which chromosome?

X

The mutation responsible for sickle-cell disease is a(n)

point mutation in the beta-globin gene

The genes in the ABO locus encode

glycosyl transferases

Which metabolite is required for normal production of the skin pigment melanin?

phenylalanine AND tyrosine

The genes for hemoglobin S and hemoglobin A are

codominant

A mutation in the gene for which enzyme is responsible for the metabolic disorder phenylketonuria?

phenylalanine hydroxylase

Which of the following is characterized as a liposomal storage disease?

Tay-Sachs disease

Amniocentesis is best performed

after the twelfth week of pregnancy

Chorionic villus sampling is best performed during which stage of pregnancy?

during the first trimester

A man and a woman, both with blood type O, get married and have a baby whose blood type is A. The man claims that he can't be the baby's father and asks for a divorce. The woman, whose genotype is H/H, i/i, insists that the child is his. For her husband to be the father of the baby, his genotype must be

h/h I to power of ((A))/i

The compulsive self-mutilation behaviors exhibited by Lesch-Nyhan individuals are the result of a mutation in the gene for which enzyme?

hypoxanthine guanine phosphoribosyltransferase

It is possible to distinguish between normal hemoglobin and hemoglobin S using electrophoresis because these two forms of hemoglobin have different

electrical charges

Bottles of Diet Coke carry a warning for people with PKU because the sweetener used in this drink contains

phenylalanine

Which of the following human diseases is caused by an autosomal recessive mutation?

phenylketonuria, cystic fibrosis, alkaptonuria, albinism

The mutation that changes normal hemoglobin to hemoglobin S changes a codon for glutamic acid to one for

valine

In a molecule of hemoglobin C, an aspartic acid residue, is changed into a ________ residue.

lysine

A child born to a man and a woman who are both carriers of the mutant allele responsible for cystic fibrosis (CF) has a ___ chance of having the disease.

25%

A methionine auxotroph

can grow on minimal medium supplemented with methionine

The autosomal disease with the signs of sinus and lung abnormalities, sterility, and sometimes dextrocardia (heart to the right of body center rather than left) is

called Kartagener syndrome and are all related to the malfunction of cilia and flagella that results from the failure of dynein motor proteins to function properly

In PKU, the absence of enzyme activity affects which step in the phenylalanine metabolism pathway?

conversion of phenylalanine to tyrosine

The one-gene-one-enzyme idea was replaced with ______________ as knowledge of gene structure improved.

one-gene-one-polypeptide

People with phenylketonuria are advised to avoid the artificial sweetener NutraSweet because it contains

phenylalanine

Women have two copies of the X chromosome, whereas men have an X and a Y chromosome. Sons always receive their X chromosome from their mother. Lesch-Nyhan syndrome is caused by a recessive mutation of a gene on the X chromosome that codes for hypoxanthine guanine phosphribosyl transferase, and that is a lethal gene. A woman heterozygous for the Lesch-Nyhan allele could have an affected

son, and grandson through her daughter

"Inborn errors of metabolism" is a phrase coined by British physician Archibald Garrod in 1908. This phrase refers to

defects in metabolic enzymes

The mutant gene responsible for Tay-Sachs disease is located on

chromosome 15

Although at least three genes are known to cause albinism, the classical mutant gene responsible for albinism in humans encodes an enzyme that converts

tyrosine to DOPA

The one-gene-one-enzyme hypothesis was proposed by ___ in 1942.

Beadle and Tatum

The study of which genetic disease led Garrod to propose that there is a special relationship between genes and enzymes?

alkaptonuria

The test organism that helped researchers elucidate the one-gene-one-enzyme hypothesis was

Neurospora crassa.

Which disease is caused by a mutation in a gene located on the X chromosome?

Lesch-Nyhan syndrome

The disease cystic fibrosis results from a defect in the Cystic Fibrosis Transmembrane Regulatory protein. Which of the following statements about the CFTR protein is FALSE?

The most common mutation causing cystic fibrosis is a deletion of a single nucleotide at position 508. This causes the deletion of a phenylalanine nucleotide at that position.

The met2, met3, met5, and met8 mutants of Neurospora all have been shown to require the amino acid methionine for growth. All of these mutants show the same phenotype when they are grown on minimal medium containing which of the following?

methionine

Mutations in genes that disrupt metabolism have been investigated for nearly 100 years, beginning with Garrod in 1902. In a model genetic organism, Neurospora, Beadle and Tatum studied biochemical mutants that were unable to grow because they could not make enzymes required to make specific metabolites. By investigating inborn errors of human metabolism, we know that often the absence of enzymes leads to the accumulation of products that cannot be eliminated and generate toxic pleiotrophic effects. Which of the following statements best explains this difference between metabolic mutations in Neurospora versus humans?

Neurospora is prototrophic and must make all of the metabolites that are essential for its growth, whereas humans are auxotrophic and require that essential metabolites be provided in the diet. Therefore, the ability to minimize the accumulation of toxic metabolites in humans is more critical to the survival of the organism.

Tay-Sachs disease is a lysosomal storage disease resulting from the lack of an enzyme called N-acetylhexosaminidase A. What are the pleiotrophic phenotypic effects associated with the deficiency of this lysosomal enzyme?

-sensitivity to sharp sounds and a red spot surrounded by a white halo on the retina of the eye
-paralysis and blindness
-loss of hearing and feeding problems
-ALL OF THESE

The most common allele associated with sickle-cell disease is the Hb-S allele. Which of the following statements about sickle-cell disease is FALSE?

-Sickle-cell disease and related forms of anemia result only from mutations in the beta chain of hemoglobin, but never from mutations in the alpha chain.
-All mutations affecting oxygen-transporting properties of hemoglobin are associated with changes in the electrophoretic properties of hemoglobin.
-The sickle-cell trait results from mutations in genes coding for the alpha subunit, whereas individuals with sickle-cell disease bear mutations in the gene coding for the beta subunit.
-ALL OF THESE FALSE

The term "pre-mRNA" refers to ____________________.

new, unprocessed mRNA of eukaryotes

During transcription, RNA polymerase joins nucleotides ____________________.

from 5' to 3'.
-Just as in DNA synthesis, RNA polymerase catalyzes the formation of a bond between a 5' phosphate on one nucleotide and a 3' hydroxyl on the next. Thus the chain grows from 5' to 3'.

In bacteria, RNA polymerase transcribes ____________________.

all types of genes

In translation,

RNA is converted to protein

Match the RNAs below with their function. Use each answer only once.
___ mRNA (a) Facilitates attachment of amino acids by ribosomes.
___ tRNA (b) Structural component of ribosomes.
___ rRNA (c) Transcripts of protein-coding genes.
___ snRNA (d) Maturation of transcripts.

mRNA (c); tRNA (a); rRNA (b); snRNA (d)

RNA molecules are ____________________.

single-stranded

The rho protein is involved in which aspect of transcription?

termination

The DNA sequence of a gene is 3'-C C A T G C T A-5'. The corresponding sequence of the mRNA produced from this gene is ____________________.

5'-G G U A C G A U-3'

The DNA sequence where RNA polymerase binds at the beginning of transcription is called the ____________________.

promoter

The major product of transcription is a molecule of ____________________.

RNA

Transcription and translation are coupled in ____________________.

bacteria

Which of the following statements is true?

Not all transcribed genes are translated to protein.

Which is a characteristic of a rho-independent terminator?

hairpin loop followed by a string of U's

Which is the best representation of the central dogma, as proposed by Francis Crick in 1956?

DNA RNA protein

Which of the following is NOT a way in which RNA differs from DNA?

RNA has nitrogenous bases bonded with the 1' carbon.
-nitrogenous bases covalently bonded to the 1' carbon, is the only feature listed that is shared with DNA.

Which of the following is not required for initiation of transcription?

primer RNA sequence

Which subunit of the RNA polymerase holoenzyme is essential for recognition of the two consensus sequences in an E. coli promoter?

s factor

Which type of RNA is involved in the splicing of pre-mRNA molecules in eukaryotic cells?

snRNA
-Snurps (snRNAs) are involved in the removal of introns from mRNA transcripts prior to translation.

There are two main forms of ß-thalassemia: ß-plus and beta-zero. ß-plus thalassemia occurs when a reduced amount of ß-globin protein is produced, while ß-zero thalassemia occurs when no ß-globin protein is produced. Which of the following mutations is most likely to result in the appearance of ß-zero thalassemia in an individual?

A single base-substitution mutation in the 5' splice site of Intron 1.

Suppose there is a single base-substitution mutation in the poly(A) tail addition site of the ß-globin gene. Assuming that this mutation has an affect on transcription, what is the most likely result of the mutation?

The reduction of ß-globin protein due to a reduction in the stability of the mRNA.

In the intron, a mutation at the 5' splice site affects the binding of which small nuclear ribonucleoprotein particle? (You must look in the "RNA Splicing Process Book" in the exercise for the answer)

U1

A mutation in the branch-point adenine affects the binding of which small nuclear ribonucleoprotein particle? (You must look in the "RNA Splicing Process Book" in the exercise for the answer)

U2

Which of the following best describes the reason why a base-substitution mutation in an intron of the ß-globin gene can result in ß-thalassemia?

The mutation affects RNA splicing, which results in a defective ß-globin protein.

During the initiation step of transcription, what molecule binds the promoter region of a DNA molecule?

RNA polymerase

During transcription, the synthesis of the mRNA strand proceeds in which direction?

5' to 3' only

Which type of RNA is found only in eukaryotes?

snRNA

What happens during the elongation step of transcription?

An RNA transcript if formed and then drops off the DNA template

Prokaryotic transcription begins when RNA polymerase binds to which site of the gene region?

-35

Which event occurs at the termination of transcription?

-RNA synthesis stops.
-The RNA chain is released from the DNA.
-RNA polymerase is released from the DNA.
-ALL OF THESE

Which of the following is not found in a eukaryotic promoter?

-10 box

In eukaryotes, where does transcription take place?

In the nucleus

In eukaryotes, precursor mRNA molecules are processed in the

nucleus

The single strand of mRNA that is produced during transcription has the same polarity as the _______ strand of DNA.

nontemplate

The sigma factor of RNA polymerase is necessary for

specific recognition of promoter elements.

A prokaryotic mRNA transcript

-is ready to be translated as soon as it is transcribed.
-undergoes coupling of transcription and translation.
-BOTH

Which parts of a eukaryotic gene are transcribed?

Both exons and introns

In eukaryotes, the initiation complex binds DNA at the

TATA box.

The process by which genetic information is transferred from DNA to RNA is called

transcription

During the initiation step of transcription, what molecule binds the promoter region of a DNA molecule?

RNA polymerase

Prokaryotic transcription begins when RNA polymerase binds to which site of the gene region?

+1

The sigma factor of RNA polymerase is necessary for

specific recognition of promoter elements.

Molecules of tRNA are

-75 to 90 nucleotides in length.
-single-stranded with secondary structure.
-cloverleaf in shape.
-synthesized with modified bases.
-ALL OF ABOVE

The function of a ribosome is

to hold mRNA and tRNAs in the correct positions to enable translation.

Which of the following is a characteristic of a rho-dependent terminator?

Termination requires ATP

Which of the following is the correct statement.

A promoter is a noncoding regulatory part of a gene.

Which of the following are correct statements.

None of the above are correct
-In Eukaryotes, mature mRNAs typically have introns, a 5' cap, and a polyA tail.
-Before a prokaryotic mRNA can be translated, t must be modified by the addition of a polyA tail.
-Histone proteins play a critical role in RNA splicing

Prokaryotic mRNA

is polycistronic

During transcription, RNA polymerase joins nucleotides

from 5' to 3'.

The consensus sequence for the -35 box of an E. coli promoter is 5'-T T G A C A-3'. This sequence functions to

bind RNA polymerase holoenzyme containing a specific sigma factor.

The DNA sequence where RNA polymerase binds at the beginning of transcription is called the

promoter

Which of the following statements is true?

Not all transcribed genes are translated to protein.

Which of the following is NOT required for initiation of transcription?

primer RNA sequence

Which subunit of the RNA polymerase holoenzyme is essential for recognition of the two consensus sequences in an E. coli promoter?

s factor

Which type of RNA is involved in the splicing of pre-mRNA molecules in eukaryotic cells?

snRNA

Which type of RNA polymerase sigma factor predominates during the heat shock response?

s32

The isolation of temperature-sensitive mutants has been a common tool of molecular genetics. TS-mutants make proteins that function normally at lower temperature but cannot function at higher temperatures. A TS-mutant of a mouse was recently isolated that had a curious property: at the higher temperature, almost all of the transfer RNA was missing from cells. You hypothesize that this is a TS-mutant in an RNA polymerase. How would you verify your hypothesis?

Determine whether RNA polymerase III activity decreases as temperature increases in the TS-mutant.

Working in a coroner's office, you are investigating the mysterious death of a person found in a wooded area in the spring of the year. During a cellular analysis of this body, you learn that the levels of mRNA that can be obtained from critical tissues are very low, and you find mushrooms in the contents of the stomach. After examination of the mushrooms, you learn that they are a species of Aminita, and a search of the Internet reveals that a toxin in this fungus inhibits RNA polymerase. However, this isn't very specific information. To be more certain of the cause of death in this case ,you would need to verify that alpha-aminitin inhibits which eukaryotic RNA polymerase?

RNA polymerase II

In eukaryotes, transcription is initiated by the formation of a preinitiation complex of transcription factors and RNA polymerase at the TATA box of the promoter. Give the correct order of the steps below.
(a) The TFIID complex containing the TATA box binding proteins binds to the TATA box.
(b) TFIIA and TFII B bind to the initiation complex.
(c) RNA polymerase begins transcribing the sense strand of the DNA producing a complementary RNA.
(d) TFIIE and TRIIH bind to the complex, and the helicase function of TRIIH produces a small bubble in the double-stranded DNA.
(e)TFIIF binds to RNA polymerase, and this complex adds to the complex assembling at the TATA box

(a) > (b) > (e) > (d) > (c)

In the maize alcohol dehydrogenase gene, there are sequences found in the 5'-untranslated region, the first 26 codons of the protein-coding region, and in the 3'-untranslated regions of the gene that are responsible for determining that this gene is transcribed only during anaerobic conditions and for determining how many copies of the mRNA for this gene are made per cell. These sequences would be considered __________.

Enhancer sequences

The addition of 7-methyl guanosine to the 5' end of a pre-mRNA during translation by a 5' to 5' linkage is referred to as capping. What would you expect to be the phenotype of a mutation in the capping enzyme that adds the 5' cap?

The 5' cap remains throughout processing of the pre-mRNA and is present in the mature mRNA, protecting it against degradation by exonucleases; and the 5' cap is important for the binding of the mRNA to the ribosome as an initial step of translation.

Which of the nucleotides found in a completed mRNA were NOT transcribed from the DNA sequence coding for the gene?

the A nucleotides in the poly (A) tail

Which of the following steps is responsible for the production of an active spliceosome during the splicing of introns?

Dissociation of the U4 snRNP from the spliceosome complex is the activating step leading to removal of the intron, the formation of a "lariat," and an mRNA with the intron spliced out.

A series of three mutants in the CAM5 gene of Arabidopsis thaliana were recently isolated. Examination of the molecular properties of these three mutants revealed the following: in mutant cam5-1,a piece of extra DNA was inserted into the CAM5 gene DNA 3 nucleotides before the single intron in this gene; in the cam5-2 gene, the extra piece of DNA was inserted between the G and U at the 5' splice junction of the intron; and in the cam5-3 gene, the extra piece of DNA was inserted in the middle of the intron at least 20 nucleotides away from both the splice junctions and the upstream branching sequence. Based on what you know about intron splicing, predict which of these mutants might produce a completely normal CAM5 mRNA.

cam5-3

A polysome contains ____________________.

-mRNA
-tRNA
-rRNA
-ALL OF ABOVE

A sequence of 3 bases in DNA has the sequence CGT. What is the corresponding tRNA anticodon for this sequence?

CGU

A tRNA molecule carries the anticodon UGC. What is the corresponding codon in mRNA?

GCA

Before any kind of post-translational processing occurs, all polypeptides begin with the amino acid ____________________.

methionine

In eukaryotes, some protein are synthesized on the ___________ and modified in the ____________________.

endoplasmic reticulum; Golgi complex.

How long, in amino acids, would be a polypeptide produced in the translation of a 24-base mRNA molecule?

7

In prokaryotes, the upstream mRNA sequence required for the initiation of protein synthesis is the ___ sequence.

Shine-Dalgarno

In the genetic code, the codon ___ is a stop codon.

UAA

In the genetic code, the codon that signifies the start of translation is ____________________.

AUG

In the genetic code, the codon UAG signifies which amino acid?

none...stop codon

Proteins are constructed from which molecular "building block?"

amino acids

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