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Biology 311C > Unit 4 Homework > Flashcards

Unit 4 Homework Flashcards

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1
Q

Beginning with a fertilized egg (zygote), how many cells would be present in an embryo following a series of five cell divisions?

A

32

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2
Q

A cell in G2 of the cell division cycle contains 20 chromatids. How many centromeres are present in this cell?

A

10

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3
Q

Taxol is an anticancer drug extracted from the Pacific yew tree that binds to microtubules and prevents their depolymerization. Which phase of mitosis or cell division would be inhibited by treatment with Taxol?

A

metaphase

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4
Q

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 12 picograms of DNA per nucleus. How many picograms of DNA would be found in a nucleus at the end of G1 and the end of G2?

A

12; 24

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5
Q

Where are the motor proteins that move chromosomes toward the poles of the mitotic spindle located?

A

on the kinetochores only

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6
Q

If a cell has completed the first meiotic division and is just beginning meiosis II, which of the following statements describes the genetic or chromosomal contents of this cell?

A

It has half the amount of DNA of the cell that began meiosis.

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7
Q

Which of the following events might result in a human zygote with 45 chromosomes?

A

an error in either egg or sperm meiotic anaphase

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8
Q

How do cells at the completion of meiosis compare with cells that have replicated their DNA and are just about to begin meiosis?

A

They have half the number of chromosomes and one-fourth the amount of DNA.

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9
Q

Which of the following processes happens during meiosis I?

A

Homologous chromosomes of a pair are separated from each other.

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10
Q

Chromatids are separated from each other during which of the following processes?

A

during both mitosis and meiosis II

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11
Q

Differences between DNA and Protein?

A

DNA contains phosphorus, protain does not.

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12
Q

Chargaff’s rule regarding DNA?

A

The percentages of adenine and thymine are roughly equal, as are the percentages of guanine and cytosine in the DNA of a given species.

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13
Q

“antiparallel” strands of nucleic acids that make up DNA

A

The 5’ to 3’ direction of one strand runs counter to the 5’ to 3’ direction of the other strand.

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14
Q

How do the leading and the lagging strands of DNA formed during DNA replication differ?

A

The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

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15
Q

What is the function of topoisomerase?

A

relieving strain in the DNA ahead of the replication fork

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16
Q

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

A

It joins Okazaki fragments together.

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17
Q

During DNA replication in E. coli, which of the following enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3’ end of Okazaki fragments?

A

DNA polymerase I

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18
Q

Which of the following mechanisms removes nucleotides that are paired incorrectly during DNA replication?

A

mismatch repair

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19
Q

During DNA replication, which of the following enzymes separates the DNA strands during replication?

A

Helicase

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20
Q

Which of the following statements correctly defines the process of gene expression?

A

Gene expression is the process by which DNA directs the synthesis of proteins.

21
Q

A particular triplet of bases in the template strand of DNA is 5’-AGT-3’. The corresponding codon for the mRNA transcribed is

A

3’-UCA-5’

22
Q

Which of the following processes only occurs in eukaryotic gene expression?

A

A poly-A tail is added to the 3’ end of an mRNA, and a cap is added to the 5’ end

23
Q

Which of the following processes only occurs in eukaryotic gene expression?

A

A poly-A tail is added to the 3’ end of an mRNA, and a cap is added to the 5’ end.

24
Q

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

A

several transcription factors

25
Q

A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. Which of the following statements best explains this fact?

A

Many noncoding stretches of nucleotides are present in eukaryotic DNA.

26
Q

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

A

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

27
Q

Examine the simple metabolic pathway in the figure above. According to Beadle and Tatum’s hypothesis, how many genes are necessary for this pathway?

A

A -> B -> C

2

28
Q

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5’-CCG-ACG-3’ (mRNA). The charged transfer RNA molecules shown in the figure below (with their anticodons shown in the 3’ to 5’ direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form.

The dipeptide that will form will be

A

alanine-alanine

29
Q

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) already in the ribosome. Where does tRNA #2 move to after this bonding of lysine to the polypeptide?

A

E site

30
Q

Which of the following statements correctly describes the role of a molecule that controls a repressible operon?

A

The molecule binds to the repressor protein and activates it.

31
Q

Which of the following must occur in order for a repressible operon to be transcribed?

A

RNA polymerase must bind to the promoter, and the repressor must be inactive.

32
Q

Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following processes occurs when the lactose enters the cell?

A

Allolactose binds to the repressor protein.

33
Q

Which of the following mechanisms is used to coordinate the expression of multiple, related genes in eukaryotic cells?

A

A specific combination of control elements in each gene’s enhancer coordinates the simultaneous activation of the genes.

34
Q

What effect does methylation have on DNA?

A

It makes it transcriptionally inactive.

35
Q

Which of the following statements correctly describes the role of general transcription factors in eukaryotes?

A

They bind to other proteins or to a sequence element within the promoter called the TATA box.

36
Q

Gene expression might be altered based on post-transcriptional processing in eukaryotes rather than prokaryotes. Which of the following statements describes this difference?

A

Eukaryotic exons may be spliced in alternative patterns.

37
Q

You are given an experimental problem involving control of a gene’s expression in the embryo of a particular species. One of your first questions is whether the gene’s expression is controlled at the level of transcription or translation. Which of the following experiments might best give you an answer?

A

You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.

38
Q

Which of the following statements describes one of the functions of the protein called ubiquitin?

A

It attaches to proteins that are marked for destruction in the cell.

39
Q

Which of the following activities can prokaryotes carry out in response to certain chemical signals?

A

alter the level of production of various enzymes

40
Q

Which order of the following steps provides the most logical sequence to follow when splicing foreign DNA into a plasmid and inserting the plasmid into a bacterium?

I. Transform bacteria with a recombinant DNA molecule.
II. Cut the plasmid DNA using restriction enzymes (endonucleases).
III. Extract plasmid DNA from bacterial cells.
IV. Hydrogen-bond the plasmid DNA to non-plasmid DNA fragments.
V. Use ligase to seal plasmid DNA to non-plasmid DNA.

A

III, II, IV, V, I

41
Q

Use the following information to answer the question.

In an effort to produce large amounts of a eukaryotic gene product, a plasmid that contains both a eukaryotic gene of interest and an antibiotic resistant gene was constructed. A transformation was performed to attempt to insert the plasmid into the bacterium, E. coli. Which of the following describes a growth condition and culture analysis that supports the claim that plasmid has entered the E. coli bacterial cell.

C Nutrient broth plus antibiotic Bacterial cells multiply

A

C

42
Q

Which of the following enzymes is required to make complementary DNA (cDNA)from RNA?

A

reverse transcriptase

43
Q

The cloning of Dolly the sheep is an example of which of the following processes?

A

transfer of an adult cell’s nucleus into an enucleated sheep egg, followed by incubation in a surrogate

44
Q

Gene therapy requires the ability to do which of the following?

A

introduce the normal allele into the patient

45
Q

In animals, what is the difference between reproductive cloning and therapeutic cloning?

A

Only therapeutic cloning supplies cells for repair of diseased or injured organs.

46
Q

A piece of DNA was incubated with a restriction enzyme called Hind III. The restriction enzyme digestion produced eight different size fragments that were separated by gel electrophoresis.

Which of the following observations correctly describes characteristics of the outcomes of this process?

A

When separated by gel electrophoresis, the pattern of DNA bands specific to Hind III digestion; repeating the process using a different restriction enzyme would not produce these fragments.

47
Q

Which of the following techniques involves reverse transcriptase, PCR amplification, and gel electrophoresis?

A

RT-PCR

48
Q

Which of the following results can a DNA microarray assay detect or identify?

A

They allow the expression of many or even all of the genes in a genome to be compared at once.

49
Q

In a genome-wide expression study using a DNA microarray assay, what is each spot used to detect?

A

the expression of a specific gene by a cell

Biology 311C (10 decks)

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