Bio 121 14,15,16,17

Front 1

What is the difference between a monohybrid cross and a dihybrid cross?

Back 1

A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid only one.

Front 2

Why did the improvement of microscopy techniques in the late 1800s set the stage for the emergence of modern genetics?

Back 2

It allowed the study of meiosis and mitosis, revealing parallels between behaviors of genes and chromosomes.

Front 3

Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because

Back 3

genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

Front 4

For a couple of decades, biologists knew the nucleus contained DNA and proteins. The prevailing opinion was that the genetic material was proteins, and not DNA. The reason for this belief was that proteins are more complex than DNA. What was the basis of this thinking?

Back 4

Proteins have a greater variety of three-dimensional forms than does DNA.

Front 5

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

Back 5

Traits are inherited in discrete units, and are not the results of "blending."

Front 6

Males are more often affected by sex-linked traits than females because

Back 6

males are hemizygous for the X chromosome.

Front 7

A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?

Back 7

an accumulation of A and no production of B and C

Front 8

What does transformation involve in bacteria?

Back 8

assimilation of external DNA into a cell

Front 9

Two characters that appear in a 9:3:3:1 ratio in the F2generation should have which of the following properties?

Back 9

The genes controlling the characters obey the law of independent assortment.

Front 10

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having

cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes

Back 10

100%

Front 11

If A, B, and C are all required for growth, a strain that is mutant for the gene encoding enzyme A would be able to grow on which of the following media?

Back 11

minimal medium supplemented with nutrient "A" only

Front 12

The following scientists made significant contributions to our understanding of the structure and function of DNA. Place the scientists' names in the correct chronological order, starting with the first scientist(s) to make a contribution.
I. Avery, McCarty, and MacLeod
II. Griffith
III. Hershey and Chase
IV. Meselson and Stahl
V. Watson and Crick

Back 12

II, I, III, V, IV

Front 13

Which of the following about the law of segregation is false?

Back 13

It is a method that can be used to determine the number of chromosomes in a plant

Front 14

Calico cats are female because

Back 14

a male inherits only one of the two X-linked genes controlling hair color.

Front 15

If A, B, and C are all required for growth, a strain mutant for the gene encoding enzyme B would be capable of growing on which of the following media?

Back 15

minimal medium supplemented with "C" only

Front 16

After mixing a heat-killed, phosphorescent strain of bacteria with a living non-phosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait?

Back 16

Descendants of the living cells are also phosphorescent.

Front 17

Mendel's second law of independentassortment has its basis in which of the following events of meiosis I?

Back 17

Alignment of tetrads at the equator

Front 18

A Barr body is normally found in the nucleus of which kind of human cell?

Back 18

Somatic cells of a female only

Front 19

The nitrogenous base adenine is found in all members of which group?

Back 19

ATP, RNA, and DNA

Front 20

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

Back 20

DNA contains phosphorus, but protein does not.

Front 21

Given the parentsAABBCc×AabbCc, assume simple dominance and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?

Back 21

3/4

Front 22

Sex determination in mammals is due to the SRY region of the Y chromosome. An abnormality could allow which of the following to have a male phenotype?

Back 22

Translocation of SRY to an autosome of a 46, XX individual

Front 23

Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because

Back 23

RNA acts as an expendable copy of the genetic material.

Front 24

Which of the following investigators was/were responsible for the following discovery?

Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA.

Back 24

Oswald Avery, Maclyn McCarty, and Colin MacLeod

Front 25

Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.

Back 25

Epistasis (2 or more genes affecting a phenotype) is involved.

Front 26

How would one explain a testcross involving F1dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced

Back 26

The two genes are linked.

Front 27

If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system with four different nucleotides?

Back 27

2

Front 28

Which of the following investigators was/were responsible for the following discovery?

In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Back 28

Erwin Chargaff

Front 29

How many genes would be responsible for the coats in the Labrador retriever question?

Back 29

2

Front 30

What does a frequency of recombination of 50% indicate?

Back 30

The two genes are likely to be located on different chromosomes

Front 31

The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of adenosine triphosphate and guanosine triphosphate. How many artificial mRNA 3 nucleotide codons would be possible?

Back 31

8

Front 32

When T2 phages infect bacteria and make more viruses in the presence of radioactive sulfur, what is the result?

Back 32

The viral proteins will be radioactive.

Front 33

In one type cross of black × black, the results were as follows:
9/16 black
4/16 yellow
3/16 brown
The genotype aabb must result in which of the following?

Back 33

Yellow

Front 34

What is the reason that linked genes are inherited together

Back 34

They are located close together on the same chromosome.

Front 35

The genetic code is essentially the same for all organisms. From this, one can logically assume all of the following except

Back 35

DNA was the first genetic material.

Front 36

Chargaff's analysis of the relative base composition of DNA was significant because he was able to show that

Back 36

the amount of A is always equivalent to T, and C to G.

Front 37

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white- flowered plant yields all-purple offspring. The partof the radish we eat may be oval or long, with long being the dominant characteristic.
In the F2generation of the above cross, which of the following phenotypic ratios would be expected?

Back 37

6:3:3:2:1:1

Front 38

If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis?

Back 38

1/4 of the gametes will ben+ 1, one will ben-1, and two will be n.

Front 39

The "universal" genetic code is now known to have exceptions. Evidence for this could be found if which of the following is true?

Back 39

If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).

Front 40

Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?

Back 40

the diameter of the helix

Front 41

A 1:2:1 phenotypic ratio in the F2generation of a monohybrid cross is a sign of

Back 41

incomplete dominance

Front 42

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this alteration called?

Back 42

Translocation

Front 43

Which of the following nucleotide triplets best represents a codon?

Back 43

a triplet in the same reading frame as an upstream AUG

Front 44

Why does the DNA double helix have a uniform diameter?

Back 44

Purines pair with pyrimidines.

Front 45

Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color. A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1individuals?

Back 45

TtRr–tall and pink

Front 46

In humans, male-pattern baldness is controlled by an autosomal gene that occurs in two allelic forms. AlleleHndetermines nonbaldness, and alleleHbdetermines pattern baldness. In males, because of the presence of testosterone, alleleHbis dominant overHn. If a man and woman both with genotype HnHb have a son, what is the chance that he will eventually be bald

Back 46

75%

Front 47

Which of the following is true for both prokaryotic and eukaryotic gene expression?

Back 47

RNA polymerase binds to the promoter region to begin transcription.

Front 48

Mendel and Morgan did not know about the structure of DNA; however, which of the following of their contributions was (were) necessary to Watson and Crick?

Back 48

the particulate nature of the hereditary material

Front 49

Skin color in a certain species of fish is inherited via a single gene with four different alleles. How many different types of gametes would be possible in this system?

Back 49

4

Front 50

What is the source of the extra chromosome 21 in an individual with Down syndrome

Back 50

Nondisjunction or translocation in either parent

Front 51

In which of the following actions does RNA polymerase differ from DNA polymerase?

Back 51

RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis.

Front 52

Replication in prokaryotes differs from replication in eukaryotes for which of these reasons?

Back 52

Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

Front 53

If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the following ratios?

Back 53

9 sharp-spined : 3 dull-spined : 4 spineless

Front 54

At which phase(s) is it preferable to obtain chromosomes to prepare a karyotype?

Back 54

Late prophase or metaphase

Front 55

Which of the following statements best describes the termination of transcription in prokaryotes?

Back 55

RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript.

Front 56

Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?

Back 56

Replication is not conservative

Front 57

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
Which of the following is a possible partial genotype for the son?

Which of the following is a possible genotype for the mother?

Back 57

IBi
IAi
B positive for the father

Front 58

RNA polymerase moves in which direction along the DNA?

Back 58

3' → 5' along the template strand

Front 59

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?

Back 59

DNA polymerase III

Front 60

Which describes the ability of a single gene to have multiple phenotypic effects?

Back 60

Pleiotropy

Front 61

RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism of such sigma switching?

Back 61

It might allow the polymerase to recognize different promoters under certain environmental conditions.

Front 62

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

Back 62

Gaps left at the 5' end of the lagging strand because of the need for a 3' onto which nucleotides can attach

Front 63

Which describes the ABO blood group system?

Back 63

Multiple alleles

Front 64

Which of these is the function of a poly (A) signal sequence?

Back 64

It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~10—35 nucleotides away.

Front 65

The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method?

Back 65

adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn

Front 66

Which of the following terms best describes when the phenotype of the heterozygote differs from the phenotypes of both homozygotes?

Back 66

Incomplete dominance

Front 67

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?

Back 67

RNA polymerase II

Front 68

The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?

Back 68

that the critical function of telomeres must be maintained

Front 69

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Whichof the following terms best describes this?

Back 69

Pleiotropy

Front 70

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

Back 70

several transcription factors (TFs)

Front 71

Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel arrays. How could these arise?

Back 71

replication without separation

Front 72

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

Back 72

Environmental factors such as soil pH

Front 73

A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which might this illustrate?

Back 73

Any mutation in the sequence is selected against.

Front 74

To repair a thymine dimmer by nucleotide excision repair, in which order do the necessary enzymes act?

Back 74

endonuclease, DNA polymerase I, DNA ligase

Front 75

Which of the following provides an example of epistasis?

Back 75

In rabbits and many other mammals, one genotype(cc) prevents any fur color from developing

Front 76

The TATA sequence is found only several nucleotides away from the start site of transcription. This most probably relates to which of the following?

Back 76

the number of hydrogen bonds between A and T in DNA

Front 77

What is the function of DNA polymerase III?

Back 77

to add nucleotides to the end of a growing DNA strand

Front 78

Most genes have many more than two alleles. However, which of the following is also true?

Back 78

There may still be only two phenotypes for the trait

Front 79

Which of the following help(s) to stabilize mRNA by inhibiting its degradation?

Back 79

5' cap and poly (A) tail

Front 80

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent...

Back 80

leading strands and Okazaki fragments.

Front 81

People with sickle-cell trait

Back 81

are heterozygous for the sickle-cell allele.
are usually healthy.
have increasedresistance to malaria.
produce normal and abnormal hemoglobin.

Front 82

What is a ribozyme?

Back 82

an RNA with enzymatic activity

Front 83

Which of the following removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

Back 83

DNA polymerase I

Front 84

The frequency of heterozygosity for the sickle cell anemia allele is unusually high,

presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?

Back 84

Darwin's explanation of natural selection

Front 85

What are the coding segments of a stretch of eukaryotic DNA called?

Back 85

exons

Front 86

Which of the following separates the DNA strands during replication?

Back 86

helicasa

Front 87

Which of the following covalently connects segments of DNA?

Back 87

ligase

Front 88

Cystic fibrosis (CF) is a Mendelian disorder in the human population that is inherited as a recessive. Two normal parents have two children with CF. The probability of their next child being normal for this characteristic is which of the following?

Back 88

1/4

Front 89

A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that

Back 89

many noncoding stretches of nucleotides are present in mRNA.

Front 90

Which of the following synthesies short segments of RNA?

Back 90

primase

Front 91

Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot

appropriately metabolize a particular amino acid. This amino acid is not otherwise produced by humans. Therefore the most efficient and effective treatment is which of the following?

Back 91

Regulate the diet of the affected persons to severely limit the uptake of the amino acid.

Front 92

Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes

Back 92

excision of introns.

Front 93

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that

Back 93

the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

Front 94

Hutchinson-Gilford progeria is anexceedingly rare human genetic disorder in which there is very early senility, and death, usually of coronary artery disease, at an average age of approximately 13. Patients, who look very old even as children, do not live to reproduce. Which of the following represents the most likely assumption?

Back 94

The disorder may be due to mutation in a single protein-coding gene

Front 95

Introns are significant to biological evolution because

Back 95

their presence allows exons to be shuffled.

Front 96

The leading and the lagging strands differ in that...

Back 96

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagginc strand is synthesized in the opposhte direction.

Front 97

One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant, although it may be either mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?

Back 97

One of the parents has very mild expression of the gene

Front 98

A mutation in which of the following parts of a gene is likely to be most damaging to a cell?

Back 98

exon

Front 99

Which of the following best describes the addition of nucleotides to a growing DNA chain?

Back 99

A nucleoside triphosphate is added to the 3' end of the DNA, releasing a molecule of pyrophosphate.

Front 100

Which of the following is (are) true of snRNPs?

Back 100

They join together to form a large structure called the spliceosome.

Front 101

A nucleoside triphosphate is added to the 3' end of the DNA, releasing a molecule of pyrophosphate.

Back 101

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

Front 102

During splicing, which molecular component of the spliceosome catalyzes the excision reaction?

Back 102

RNA

Front 103

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

Back 103

single-strand binding proteins

Front 104

Alternative RNA splicing

Back 104

can allow the production of proteins of different sizes from a single mRNA.

Front 105

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells have which impaired ability?

Back 105

They cannot repair thymine dimers.

Front 106

In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?

Back 106

the various domains of the polypeptide product

Front 107

Which would you expect of a eukaryotic cell lacking telomerase?

Back 107

a reduction in chromosome length

Front 108

Each eukaryotic mRNA, even after post-transcriptional modification, includes 5' and 3' UTRs. Which are these?

Back 108

the untranslated regions at either end of the coding sequence

Front 109

Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication?

Back 109

double-stranded DNA, 4 kinds of dNTPs, primers, origins

Front 110

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly(A) tail. Which of the following would you expect him to find?

Back 110

The molecule is digested by exonucleases since it is no longer protected at the 5' end.

Front 111

Studies of nucleosomes have shown that histones (except H1) exist in each nucleosome as two kinds of tetramers: one of 2 H2A molecules and 2 H2B molecules, and the other as 2 H3 and 2 H4 molecules. Which of the following is supported by this data?

Back 111

The two types of tetramers associate to form an octamer.

Front 112

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

Back 112

AAA

Front 113

When DNA is compacted by histones into 10 nm and 30 nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?

Back 113

methylation and phosphorylation of histone tails

Front 114

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

Back 114

C) bonding of the anticodon to the codon.
D) attachment of amino acids to tRNAs.
E) both C and D

Front 115

In prophase I of meiosis in female Drosophila, studies have shown that there is phosphorylation of an amino acid in the tails of histones. A mutation in flies that interferes with this process results in sterility. Which of the following is the most likely hypothesis?

Back 115

Histone tail phosphorylation prohibits chromosome condensation.

Front 116

The tRNA shown in Figure 17.4 has its 3' end projecting beyond its 5' end. What will occur at this 3' end?

Back 116

The amino acid binds covalently.

Front 117

In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?

Back 117

the 30 nm chromatin fiber

Front 118

A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of a phenylalanine. The consequence of this for the cell will be that

Back 118

proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

Front 119

Which of the following statements describes the eukaryotic chromosome?

Back 119

It consists of a single linear molecule of double-stranded DNA.

Front 120

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

Back 120

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

Front 121

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

Back 121

The cell's DNA couldn't be packed into its nucleus.

Front 122

What is the most abundant type of RNA?

Back 122

rRNA

Front 123

Which of the following statements describes histones?

Back 123

Histone H1 is not present in the nucleosome bead; instead it is involved in the formation of higher-level chromatin structures.

Front 124

From the following list, which is the first event in translation in eukaryotes?

Back 124

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

Front 125

Why do histones bind tightly to DNA?

Back 125

Histones are positively charged, and DNA is negatively charged.

Front 126

Choose the answer that has these events of protein synthesis in the proper sequence.
1. An aminoacyl-tRNA binds to the A site.
2. A peptide bond forms between the new amino acid and a polypeptide chain.
3. tRNA leaves the P site, and the P site remains vacant.
4. A small ribosomal subunit binds with mRNA.
5. tRNA translocates to the P site.

Back 126

4, 1, 2, 5, 3

Front 127

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

Back 127

nucleosome, 30-nm chromatin fiber, looped domain

Front 128

As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs?

Back 128

The tRNA that was in the A site moves into the P site.

Front 129

Which of the following statements is true of chromatin?

Back 129

Heterochromatin is highly condensed, whereas euchromatin is less compact.

Front 130

What are polyribosomes?

Back 130

groups of ribosomes reading a single mRNA simultaneously

Front 131

A biochemist isolates and purifies various molecules needed for DNA replication. When she adds some DNA, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

Back 131

DNA ligase

Front 132

Which of the following is a function of a signal peptide?

Back 132

to translocate polypeptides across the ER membrane

Front 133

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

Back 133

DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

Front 134

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by

Back 134

a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.

Front 135

The elongation of the leading strand during DNA synthesis

Back 135

depends on the action of DNA polymerase.

Front 136

When does translation begin in prokaryotic cells?

Back 136

as soon as transcription has begun

Front 137

The spontaneous loss of amino groups from adenine results in hypoxanthine, an uncommon base, opposite thymine in DNA. What combination of molecules could repair such damage?

Back 137

nuclease, DNA polymerase, DNA ligase

Front 138

When a tRNA molecule is shown twisted into an L shape, the form represented is

Back 138

its 3-dimensional shape.

Front 139

In a nucleosome, the DNA is wrapped around

Back 139

histones

Front 140

An experimenter has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. Which of the following hypotheses describes the most likely result?

Back 140

The amino acid methionine will not bind.

Front 141

A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already.

Which enzyme causes a covalent bond to attach lysine to the polypeptide?

Back 141

peptidyl transferase

Front 142

Where does tRNA #2 move to after this bonding of lysine to the polypeptide?

Back 142

Exit tunnel

Front 143

Which component of the complex described enters the exit tunnel through the large subunit of the ribosome?

Back 143

newly formed polypeptide

Front 144

The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following?

Back 144

polypeptide factors plus GTP

Front 145

When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate?

Back 145

an assembled ribosome with a polypeptide attached to the tRNA in the P site

Front 146

Why might a point mutation in DNA make a difference in the level of protein's activity?

Back 146

It might substitute an amino acid in the active site.

Front 147

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

Back 147

a deletion of 2 nucleotides

Front 148

What is the effect of a nonsense mutation in a gene?

Back 148

It introduces a premature stop codon into the mRNA.

Front 149

Each of the following options is a modification of the sentence THECATATETHERAT. Which of the following is analogous to a frameshift mutation?

Back 149

THECATATTHERAT

Front 150

Each of the following options is a modification of the sentence THECATATETHERAT. Which of the following is analogous to a single substitution mutation?

Back 150

THECATARETHERAT

Front 151

Sickle-cell disease is probably the result of which kind of mutation?

Back 151

point

Front 152

A frameshift mutation could result from

Back 152

either an insertion or a deletion of a base.

Front 153

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?

Back 153

a base-pair deletion

Front 154

Which point mutation would be most likely to have a catastrophic effect on the functioning of a protein?

Back 154

a base deletion near the start of a gene

Front 155

Which of the following statements are true about protein synthesis in prokaryotes?

Back 155

Translation can begin while transcription is still in progress.

Front 156

Of the following, which is the most current description of a gene?

Back 156

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

Front 157

In eukaryotic cells, transcription cannot begin until

Back 157

several transcription factors have bound to the promoter.

Front 158

Which of the following is not true of a codon?

Back 158

It extends from one end of a tRNA molecule.

Front 159

The anticodon of a particular tRNA molecule is

Back 159

complementary to the corresponding mRNA codon.

Front 160

Which of the following is not true of RNA processing?

Back 160

Exons are cut out before mRNA leaves the nucleus.

Front 161

Which of the following mutations would be most likely to have a harmful effect on an organism?

Back 161

a single nucleotide insertion downstream of, and close to, the start of the coding sequence

Front 162

Which component is not directly involved in translation?

Back 162

DNA