Bios 1700 Chapter 12

Given that the rate of DNA synthesis of a plasmid in yeast is 50 nucleotides per second and the circular plasmid replicates in 20 minutes, what is the approximate maximum size of the plasmid?

120,000 bp

A new nucleotide can only be added to the _____ end of a growing DNA strand. DNA therefore always grows in the _____ direction.

3'; 5' to 3'

The leading strand is the daughter strand that has its _____ end pointed toward the replication fork and is therefore synthesized _____.

3'; continuously

You run a PCR reaction for five cycles starting with a single DNA duplex. Theoretically, how many copies of your sequence would you now have?

32

The lagging strand is the daughter strand that has its _____ end pointed toward the replication fork and is therefore synthesized _____.

5'; in a series of segments

Production of a recombinant DNA molecule makes use of which of these properties of DNA?

A restriction enzyme cleaves duplex DNA molecules only at the positions of certain short sequences that constitute the enzyme's restrictions site. DNA ligase is an enzyme that can join the ends of single-stranded DNA molecules. DNA polymerase elongates a growing DNA strand by the addition of successive deoxynucleotides to the 3' end. Complementary single-stranded nucleic acid sequences can come together to form a duplex molecule.

Which of the statements is true regarding DNA replication of a linear chromosome?

Both strands get shortened at opposite ends during replication.

One method for changing the DNA sequence of a gene in its original location in the cell uses a type of technology known as:

CRISPR-Cas9.

Which factors make amplification of a DNA fragment by means of the polymerase chain reaction possible? Select all that apply.

Complementary single-stranded nucleic acid sequences can come together to form a duplex molecule. DNA polymerase elongates a growing DNA strand by the addition of successive deoxynucleotides to the 3' end.

Which enzyme is the first to bind to the DNA sequences at the origin of replication?

DNA helicase

Why are primers needed for DNA replication?

DNA polymerase can only add nucleotides to an existing chain.

The enzyme responsible for proofreading a growing DNA strand and for replacing mismatched nucleotides is

DNA polymerase.

The enzyme responsible for proofreading a growing DNA strand and for replacing mismatched nucleotides is:

DNA polymerase.

The enzyme responsible for replacing RNA primers with DNA is a type of:

DNA polymerase.

Which factors make sequencing by the Sanger chain-termination method possible? Select all that apply.

Duplex nucleic acid molecules can be separated by size by means of gel electrophoresis. Complementary single-stranded nucleic acid sequences can come together to form a duplex molecule. A DNA strand whose 3' end terminates in a dideoxynucleotide cannot be elongated. New nucleotides are added only to the 3' end of a growing DNA strand.

Imagine that a doctor is culturing two types of cells: one from a malignant melanoma and one from a normal skin sample. How would you expect these two cell populations to differ?

Malignant melanoma cells would have active telomerases that constantly replenish and lengthen telomeres.

What would happen to the variation between organisms in a population if their DNA polymerase did not have a proofreading function?

The amount of variation would increase.

You are interested in studying human ß-globin and decide to produce the protein in bacterial cells. The ß-globin gene is a relatively simple gene with a single intron. You insert the entire gene, including the gene's promoter, in a plasmid and transform the recombinant plasmid into E. coli. You are disappointed to discover that your bacterial culture does not produce the correct protein. What are some possible explanations? Select all that apply.

The bacterial cell produces the protein, but the protein is rapidly degraded. The bacterial cell does not recognize the eukaryote promoter. The bacterial cell cannot splice introns.

What would happen if telomerase stopped working in a cell in which it normally functions at high levels?

The cell would eventually die as the DNA continued to shorten.

To cells that are defective in primer removal, you add fluorescent ribonucleotides when the cells are undergoing DNA replication. In this case, you observe that one strand glows more than the other not only near the replication fork but also at intervals along its length. Which strand glows in this way and why?

The lagging strand glows in this way because its RNA primers are required for each Okazaki fragment and are closely spaced.

Suppose you add fluorescent ribonucleotides to a cell undergoing DNA replication so that the RNA primers used in DNA synthesis glow when viewed with a fluorescent microscope. You notice that, near each replication fork, one strand glows more than the other. Which strand glows more, and why?

The lagging strand glows more because its RNA primer is nearer the replication fork.

Which of the statements best describes the way you would engineer bacterial cells to produce a human protein?

Use a specific restriction enzyme to cleave both the donor DNA and the vector DNA.

The transformation step in creating bacteria genetically engineered to produce human proteins involves:

bacteria taking up the recombinant DNA in the form of the vectors.

The technique of Sanger sequencing takes advantage of the fact that dideoxynucleotides (nucleotides in which the 3' hydroxyl group is absent) act as:

chain terminators.

In gel electrophoresis, DNA fragments migrate toward the negative pole of the electric field.

false

Which of the choices is an example of a transgenic organism?

fish that "glow in the dark" by expressing fluorescent jellyfish proteins

Telomerase is fully active in _____ and _____ cells, but almost completely inactive in _____ cells.

germ; stem; somatic

In contrast to linear DNA replication, circular DNA replication typically:

has a single origin of replication.

What is the name of the enzyme that separates the two strands of DNA during replication?

helicase

A DNA molecule is cut with two different restriction enzymes known to cleave it only once each. After gel electrophoresis, three different DNA fragments are detected. This result means that the original DNA molecule was:

linear.

Each DNA parent strand within a replication bubble acts as a template strand that produces:

one leading strand and one lagging strand.

As a piece of linear DNA is replicated, the leading strand will have _____ RNA primer(s) and the lagging strand will have _____ RNA primer(s).

one; many

Which of these is necessary for the first step of PCR?

original template DNA

The extrachromosomal DNA often found in bacteria is called a:

plasmid

The type of genetic engineering that often involves isolating genes from one species and introducing them into another is called _____ technology.

recombinant DNA

In a long DNA molecule, each origin of replication produces a _____ with a _____ on each side.

replication bubble; replication fork

In gel electrophoresis, DNA fragments are separated based on their:

size

If you were able to find a drug that could inhibit the reactivation of telomerase activity in cancer cells, the cancer cells would:

slowly erode their chromosome ends.

The enzyme _____ compensates for chromosomes shortening at the tips after each round of DNA replication.

telomerase

In replication of a linear double-stranded DNA molecule, one end of each strand becomes shorter in each round of replication. This happens because:

the RNA primer cannot be replaced at the very end of a lagging DNA strand.

What feature of double-stranded DNA makes it necessary to have a leading strand and a lagging strand during replication?

the antiparallel orientation of the strands

A lack of telomerase activity limits what?

the number of times a cell can divide

Consider a cell in which one of the proteins or enzymes involved in DNA replication is altered in a way that results in an increased rate of single-base changes in the newly synthesized DNA strand. Which function of which protein is most likely disrupted in this situation?

the proofreading function of DNA polymerase

In gel electrophoresis, DNA fragments are separated based on:

their size.

Organisms that have been modified to contain DNA from other species are known as:

transgenic organisms.

In circular DNA, the DNA molecule is not shortened during each round of replication.

true

The presence of Okazaki fragments demonstrates the antiparallel nature of the double helix.

true

When we say that DNA replication is semiconservative, we mean that:

when DNA is replicated each new double helix contains one parental strand and one newly synthesized daughter strand.