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Exam 2 (Ch 8 - Ch 10) Flashcards

1
Q

Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not?

A

Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

Unfortunately, these trisomies do occur and are commonly observed in spontaneously aborted embryos and fetuses.

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2
Q

Which of the following occurs during interphase?

A

cell growth and duplication of the chromosomes

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3
Q

The term binary fission is best applied to _____.

A

prokaryotes

Prokaryotes (such as bacteria) reproduce by a type of cell division called binary fission.

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4
Q

How many pairs of autosomes do humans have?

A

22

Humans have 22 pairs of autosomes and one pair of sex chromosomes.

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5
Q

Which of the following options correctly describes the behavior of a tetrad during anaphase I of meiosis?

A

It splits into two pairs of sister chromatids, and one pair goes to each pole of the dividing cell.

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6
Q

Nondisjunction occurs when

A

members of a chromosome pair fail to separate.

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7
Q

Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures called

A

sister chromatids.

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8
Q

Eukaryotic cells spend most of their cell cycle in which phase?

A

interphase

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9
Q

The function of meiosis is to make _____.

A

four cells with a haploid number of chromosomes

The two cell divisions of meiosis, I and II, produce four haploid daughter cells, which are not genetically identical to the diploid parent cell.

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10
Q

At the conclusion of meiosis I, the daughter cells are _____.

A

haploid and the sister chromatids are joined

The daughter cells of meiosis I are haploid, and the sister chromatids are still joined. During meiosis II, the sister chromatids separate.

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11
Q

A cell is treated with a drug that prevents the formation of intracellular (within the cell) vesicles. Which of the following processes would be blocked?

A

cytokinesis in a plant cell

Cytokinesis in plant cells would be blocked because the cell plate that ultimately separates one cell into two is formed from coalescing vesicles.

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12
Q

The kinetochores are _____.

A

sites at which microtubules attach to chromosomes

The kinetochores appear to move along the spindle fiber, dragging the attached chromosomes with them.

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13
Q

At which point do centrosomes begin to move apart to the opposite poles of the cell in a dividing human liver cell?

A

prophase

The centrosomes move away from each other during prophase, apparently propelled along the surface of the nucleus by the lengthening bundles of microtubules between them.

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14
Q

During mitosis, the chromosomes move because _____.

A

they attach to a dynamic, precisely regulated mitotic spindle

It is the extension and shortening of microtubules that are attached to opposite faces of chromosomes that controls chromosome movement.

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15
Q

One event occurring during prophase is _____.

A

the beginning of the formation of the mitotic spindle

During prophase, the mitotic spindle begins to form.

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16
Q

With the exception of identical twins, siblings who have the same two biological parents are likely to look similar, but not identical, to each other because they have

A

a similar but not identical combination of genes.

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17
Q

What is the typical result when a diploid cell undergoes meiosis?

A

four haploid cells

The two cell divisions of meiosis, I and II, produce four haploid daughter cells, which are not genetically identical to the diploid parent cell.

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18
Q

At the start of mitotic anaphase,

A

the centromeres of each chromosome come apart.

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19
Q

Independent orientation of chromosomes at metaphase I results in an increase in the number of

A

possible combinations of characteristics.

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20
Q

Two chromosomes in a nucleus that carry genes controlling the same inherited characteristics are

A

homologous chromosomes.

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21
Q

During cell division, what role do centrosomes play?

A

They organize the microtubules.

The centrosomes are the microtubule- organizing centers of the cell.

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22
Q

Crossing over occurs during _____.

A

prophase I

Crossing over that results in genetic recombination occurs during this phase.

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23
Q

During which phase of mitosis do the chromosomes line up on a plane equidistant from the two spindle poles?

A

metaphase

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24
Q

The phase of mitosis during which the chromosomes move toward separate poles of the cell is _____.

A

anaphase

Anaphase begins when the paired centromeres of each chromosome separate, liberating the sister chromatids, which begin moving toward opposite poles of the cell.

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25
An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis?
four Because of the synapsis of homologous chromosomes, the number of tetrads in meiosis will be the same as the haploid number of chromosomes.
26
Which of the following statements regarding mitosis and meiosis is false?
Mitosis produces daughter cells with half the number of chromosomes as the parent cell.
27
What must happen before a cell can begin mitosis?
The chromosomes must be duplicated. Before mitosis can begin, the chromosomes, or genetic material, must be copied, which occurs during interphase.
28
The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
Prophase Prophase is the first phase of mitosis, when the centrosomes begin moving toward opposite poles and the nuclear envelope breaks up.
29
The chromosomes line up in the center of the cell during which phase of mitosis?
Metaphase Metaphase occurs in the middle of mitosis, when the chromosomes line up in the middle of the cell.
30
The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
Anaphase Sister chromatids separate and start their migration toward opposite poles during anaphase.
31
The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
Telophase Telophase is the final phase of mitosis, when the chromosomes have arrived at the poles and the nuclear envelopes of the two new cells form.
32
At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.
cytokinesis Cytokinesis is the division of the cytoplasm that occurs in conjunction with telophase, the last phase in mitosis.
33
Mature human nerve cells and muscle cells
are permanently in a state of nondivision.
34
Cytokinesis refers to _____.
division of the cell outside the nuclear material Cytokinesis is the division of the cytoplasm.
35
After fertilization, the resulting zygote begins to divide by _____.
mitosis Mitosis ensures that all somatic cells receive copies of the parental chromosomes.
36
During which phase of mitosis does the nuclear envelope re-form?
telophase
37
According to the graph, at what maternal age does the incidence of Down syndrome begin to increase substantially?
about 37 or 38
38
Sister chromatids are
joined together at a centromere.
39
A cleavage furrow forms in an animal cell during _____.
cytokinesis Cytokinesis is usually well under way by telophase. In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two.
40
The creation of genetically identical offspring by a single parent, without the participation of sperm and egg, is called
asexual reproduction.
41
You can determine this is a plant cell rather than an animal cell because it has _____.
formed a cell plate Correct. The cell plate, which divides the cytoplasm in two, forms during telophase of mitosis in a plant cell.
42
Chromatids are _____.
identical copies of each other if they are part of the same chromosome Each duplicated chromosome consists of two identical sister chromatids.
43
When we say that an organism is haploid, we mean that _____.
its cells each have one set of chromosomes A cell with a single chromosome set is called a haploid cell.
44
Which of the following is a feature of plant cell division that distinguishes it from animal cell division?
formation of a cell plate
45
The process by which the cytoplasm of a eukaryotic cell divides to produce two cells is called
cytokinesis.
46
During which stage of meiosis do synapsis and crossing over occur?
prophase I
47
A benign and a malignant tumor differ in that _____.
cells of a benign tumor remain within the tumor, whereas cells of a malignant tumor can spread to other body tissues This is the fundamental difference between these classes of tumors.
48
In meiosis II, _____.
sister chromatids are separated This is the task of meiosis II and is the reason meiosis II resembles mitosis.
49
In the telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____.
prophase During prophase we observe the formation of the spindle, the condensation of chromatin, and the disappearance of the nucleolus.
50
Which of the following statements correctly describes the timing of DNA synthesis?
DNA is synthesized in the S phase of interphase. Single chromosomes enter the synthesis or S phase of interphase. At the end of this phase, after DNA replication, the chromosomes are double, each consisting of two sister chromatids.
51
DNA replication occurs in _____.
the S phase of interphase Chromosomes are duplicated only during the S phase. "S" stands for synthesis of DNA.
52
Looking into your microscope, you spot an unusual cell. Instead of the typical rounded cell shape, the cell has a very narrow middle separating two bulging ends. It sort of looks like the number 8! Then you realize that this cell is
undergoing cytokinesis.
53
Which of the following is found in RNA but not in DNA?
an additional hydroxyl group RNA's sugar, ribose, has an additional OH group in the 2' position (lower right on Figure 10.2C in your textbook). This OH group is missing in deoxyribose.
54
The monomers of DNA and RNA are
nucleotides.
55
Which of the following statements regarding DNA is false?
DNA uses the nitrogenous base uracil.
56
Which of the following build(s) new strands of DNA?
DNA polymerases DNA polymerases build new strands of DNA by adding DNA nucleotides one at a time.
57
Which statement about DNA replication is CORRECT?
The leading strand is built continuously, and the lagging strand is built in pieces. The leading and lagging strands are the new strands of DNA made during DNA replication. The leading strand is built continuously, and the lagging strand is built in pieces.
58
During DNA replication, which nucleotide will bind to an A nucleotide in the parental DNA?
T During DNA replication, A binds with T.
59
The molecule that seals the gaps between the pieces of DNA in the lagging strand is
DNA ligase. DNA ligase seals the gaps between the pieces of DNA in the lagging strand, turning it into a continuous strand.
60
Which statement about DNA replication is FALSE?
DNA ligase adds nucleotides to the lagging strand. You're right! This statement is FALSE. DNA ligase seals the gaps between segments of DNA in the lagging strand. It does not add nucleotides to the lagging strand.
61
During replication, the original "parent" DNA _____.
serves as the template for the creation of two complete sets of DNA As replication occurs, each side of the double helix acts as a template. Thus, each new DNA molecule includes one parent strand and one new strand.
62
DNA replication
uses each strand of a DNA molecule as a template for the creation of a new strand.
63
If one strand of DNA is CGGTAC, the corresponding strand would be
GCCATG.
64
Multiple origins of replication on the DNA molecules of eukaryotic cells serve to
shorten the time necessary for DNA replication.
65
Which of the following enzymes catalyzes the elongation of a new DNA strand?
DNA polymerase
66
Which of the following options best depicts the flow of information when a gene directs the synthesis of a cellular component?
DNA → RNA → protein
67
The transfer of genetic information from DNA to RNA is called
transcription.
68
The "one gene-one polypeptide" theory states that
the function of an individual gene is to dictate the production of a specific polypeptide.
69
The directions for each amino acid in a polypeptide are indicated by a codon that consists of ________ nucleotide(s) in an RNA molecule.
3
70
We would expect that a 15-nucleotide sequence ending with a stop codon will direct the production of a polypeptide that consists of
4 amino acids.
71
Which of the following events occurs during transcription?
A molecule of RNA is formed based on the sequence of nucleotides in DNA. During transcription, RNA nucleotides line up with their complementary DNA partners, transcribing the information in DNA into RNA.
72
Which of the following is a correct statement about mRNA?
mRNA moves from the nucleus to the cytoplasm following RNA processing. mRNA undergoes RNA processing in the nucleus and then moves to the cytoplasm for translation.
73
The site of translation is
ribosomes in the cell cytoplasm. Translation occurs at ribosomes in the cell cytoplasm.
74
Which one of the following does not play a role in translation?
DNA DNA contains the instructions for making proteins, but these instructions are transcribed to RNA before translation occurs.
75
Which of the following does not occur during RNA processing?
mRNA attaches to the small subunit of a ribosome. mRNA attaches to the small subunit of a ribosome at the beginning of translation.
76
Which of the following enzymes catalyzes the linking together of RNA nucleotides to form RNA?
RNA polymerase
77
Which of the following occurs when RNA polymerase attaches to the promoter DNA?
initiation of a new RNA molecule
78
In eukaryotic cells, the RNA is processed before it leaves the nucleus. This processing _____.
includes the addition of a cap and tail, which protect the mRNA molecule from enzymatic attack, and the removal of introns The cap and tail have many functions, which include assisting with the export of the molecule from the nucleus, helping it resist attack from cellular enzymes, and directing ribosome binding.
79
An anticodon is _____.
a set of triplet bases that is complementary to a codon triplet on mRNA The anticodon triplet of a tRNA molecule binds to its complementary codon triplet on mRNA during translation.
80
Which of the following takes place during translation?
the conversion of genetic information from the language of nucleic acids to the language of proteins
81
Any change in the nucleotide sequence of DNA is called
a mutation.
82
Consider the following sentence: "The dog did not eat." Which of the following variations of this sentence is most like a base substitution mutation?
The doe did not eat.
83
Consider the following sentence: "The dog did not eat." Which of the following variations of this sentence is most like a reading frame mutation?
The dod idn ote at.
84
A physical or chemical agent that changes the nucleotide sequence of DNA is called a(n)
mutagen.
85
The four bases contained in DNA are _____.
adenine, guanine, cytosine, thymine DNA contains four bases: adenine, guanine, cytosine, and thymine.
86
Which of the following describes a complete nucleotide?
a nitrogenous base, a sugar, and a phosphate group Each nucleotide unit of DNA consists of a nitrogenous base (A, G, C, or T), the sugar deoxyribose, and a phosphate group.
87
Which of the following is only associated with RNA?
uracil Uracil is found only in RNA.
88
The results of which of the following techniques were most helpful to Watson and Crick in determining the structure of DNA?
X-ray crystallography Watson and Crick based their model of DNA on data they were able to extract from Franklin's X-ray diffraction photo.
89
If you analyzed the nucleotide content of DNA, you would expect to find that _____.
the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1 This is a result of the specific base pairings and complementary nature of DNA's double helix.
90
Which of the following statements is true about double-stranded DNA?
The strands run in opposite directions. The two DNA strands are antiparallel to one another.
91
Two new strands of DNA molecules grow as bases are added by the enzyme _____.
DNA polymerase Elongation of new DNA is catalyzed by DNA polymerases.
92
What enzyme joins DNA fragments?
DNA ligase After DNA is unwound, DNA polymerase synthesizes the complementary strands, proofreading as it goes; ligase joins the DNA fragments.
93
A gene is usually _____.
the information for making a polypeptide The nucleotide sequence of a gene usually codes for a polypeptide; some genes encode RNA molecules that are never translated, such as tRNA.
94
There are six different codons that code for the amino acid leucine in a protein. Because of this, we say that the code is _____.
redundant There is redundancy in the code, allowing more than one codon to specify a single amino acid.
95
In order for transcription to occur in a strand of a DNA molecule, there would have to be a specific recognition sequence, called a(n) _____, upstream of the DNA sequence.
promoter The region of DNA to which RNA polymerase attaches and initiates transcription is the promoter, which typically extends several dozen nucleotides "upstream" from the start point.
96
Genetic information is transferred from the nucleus to the cytoplasm of eukaryotic cells in the form of _____.
nucleic acids In transcription, a gene provides the instructions for synthesizing an mRNA molecule, a polynucleotide, that enters the cytoplasm to be translated.
97
What is the proper order of the following events in the expression of a eukaryotic gene?
transcription, RNA processing, translation In eukaryotic cells, the transcription of a pre-mRNA is followed by processing. The mRNA then moves to the cytoplasm, where ribosomes construct a polypeptide based on the codons in the RNA.
98
The function of tRNA during protein synthesis is to _____.
deliver amino acids to their proper site during protein synthesis Each tRNA molecule is used repeatedly, picking up its designated amino acid in the cytosol, depositing this cargo at the ribosome, and leaving the ribosome to pick up another load.
99
The P site of a ribosome _____.
holds the growing polypeptide chain Correct. The P site (peptidyl-tRNA site) holds the tRNA carrying the growing polypeptide chain, whereas the A site (aminoacyl-tRNA site) holds the tRNA carrying the next amino acid to be added to the chain.
100
As shown below, during polypeptide synthesis a ribosome holds two transfer RNAs in its binding sites. One tRNA has a polypeptide chain attached to it; the other tRNA has a single amino acid attached to it. What happens next?
The polypeptide chain moves over and bonds to the single amino acid. Correct. The ribosome shifts one codon. As it does so, the growing polypeptide is bonded to the amino acid on the next tRNA.
101
The figure below shows the initiation of translation. The first amino acid inserted into a new polypeptide chain in eukaryotic cells is always _____.
methionine Correct. The initiator tRNA, which carries the amino acid methionine, attaches to the initiation codon.
102
A virus infects a cell and randomly inserts many short segments of DNA containing a stop codon throughout the organism's chromosomes. This will probably cause _____.
manufactured proteins to be short and defective Alterations that change an existing codon or insert a stop codon cause a premature termination of the polypeptides.
103
During the process of translation, _____ matches an mRNA codon with the proper amino acid.
transfer RNA The mRNA codon binds to the complementary anticodon of a tRNA carrying the appropriate amino acid.

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