Bio 110 Chapter 13

Describe the process of DNA replication

1) 2 DNA strands are separated at the origin of replication, opening up a replication bubble. Binding proteins keep the DNA open 2) DNA polymerase catalyze the elongation of new DNA at the replication fork 3) Primase starts and RNA chain with a single RNA nucleotide and adds RNA nucleotides one at a time using the parental DNA template 4) Lagging- DNA polymerase must add nucleotides in the direction away from the replication fork 5) it is synthesized as a series of segments using Okazaki fragments. After the formation of the fragments, DNA polymerase I removed the RNA primers and replaces the nucleotides with DNA 6) remaning gaps are joined by DNA ligase

What are Chargaff's rules?

1) the base composition of DNA varies between species 2) in any species, A always equals T and C always equals G

How is chromatin packed into DNA?

8 histones wrap around the chromatin. A nucleosome is DNA wound twice around the 8 histones

What are base pairing rules?

A and T (purine adenin always pairs with pyrimidine thymine) G and C (purine guanine always pairs with pyrimidine cytosine)

Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA? a) griffith b) franklin c) meselon and stahl d) chargaff e) mcclintock

B) franklin

What is the relationship between telomeres and telomerase? How does an increased in activated telomerase lead to cancer?

Eukaryotic chromosomal DNA molecules have telomeres at their ends. Telomeres consist of multiple repetitions of one short nucleotide sequence. Telomerase is an enzyme and is not active in most human somatic cells. By activating telomerase in cells, cells are immortalized and can divide endlessly. Telomerase is present in many human tumor samples.

What was Griffith's experiment and how did it contribute to our understanding of DNA?

He worked with two strains of bacterium, one pathogenic and one harmless. He killed the pathogenic bacterium with heat and mixed the cell remains with the living nonpathogenic bacterium. This caused some cells to become pathogenic. This was evidence of transformation- a change in genotype and phenotype due to assimilation of foreign DNA

What was Hershey and Chase's experiment and how did it contribute to our understanding of DNA?

Hershey and Chase performed experiments showing that DNA is the genetic material of a phage known as T2. They showed that only the DNA of the T2 phage, not the protein, enters and E.coli during infection. This proved that nucleic acids are hereditary material

What side does DNA polymerase add nucleotides to?

Nucleotides are only added to the free 3' end of a growing strand. DNA can ONLY elongate in the 5' to 3' direction

What process allows scientists to perform DNA replication in the laboratory?

Polymerase chain reactions can be used to perform DNA replication in the lab. First, the reaction mixture is heated to denature the DNA strands. Then, it is cooled to allow annealing of short single stranded DNA primers that are complementary to the sequences on the opposite strands. Lastly, a DNA polymerase extends the primers in the 5' -3' direction.

Describe Semiconservative DNA replication

Specific base pairings are the mechanism for genetic material. Each strand act as a template for building a new strand during replication. In DNA, one strand is old and one is new.

What is the function of telomeres?

Telomeres are short nucleotide sequences that help protect the ends of DNA. Their goal is to prevent the shortening of DNA molecules

What scientists introduced the structure of DNA

Watson, Crick, and Franklin

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? a) DNA polymerase can join new nucleotides only to the 3' end of a preexisting strand b) helicases and single stranded binding proteins work at the 5' end c) the origins of replication occur only at the 5' end d) DNA ligase works only in the 3'-5' direction

a) DNA polymerase can join new nucleotides only to the 3' end of a preexisting strand

Which of the following statements accurately describes why Taq polymerase is used in PCR? a) it is heat stable and can withstand the heating step of PCR b) only minute amounts are needed for each cycle of PCR c) it binds more readily than other polymerases to the primers d) it has regions that are complementary to the primers

a) it is heat stable and can withstand the heating steps of PCR

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage? a) nuclease, DNA polymerase, DNA ligase b) topoisomerase, primase, DNA polymerase c) topoisomerase, helicase,single stranded binding protein d) DNA ligase, replication fork proteins, adenyly cyclase

a) nuclease, DNA polymerase, DNA ligase

which of the following lists of structures correctly represents the order of increasingly higher levels of organization of chromatin? a) nucleosome, 30nm chromatin fiber, looped domain b) looped domain, 30nm chromatin fiber, nucleosome c) looped domain, nucleosome, 30nm chromatin fiber d) nucleosome, looped domain, 30nm chromatin fiber e) 30nm chromatin fiber, nucleosome, looped domain

a) nucleosome, 30nm chromatin fiber, looped domain

If a cell were unable to produce histone proteins, which of the following would be a likely effect? a) the cell's DNA couldn't be packed into its nucleus b) spindle fibers would not form during prophase c) expression of other genes would compensate for the lack of histones d) DNA polymerase I would not function properly

a) the cell's DNA couldn't be packed into its nucleus

How do the leading and the lagging strands 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 b) the leading strand is synthesized at twice the rate of the lagging strand c) the leading strand is synthesized in short fragments that are ultimately stitched together, whereas the lagging strand is synthesized continuously d) the leading strand is synthesized by adding nucleotides to the 3 end of the growing strand and the lagging strand is synthesized by adding nucleotides to the 5 end

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

DNA replication overall has very high fidelity. which of the following phenomena or processes contribute to this high fidelity? more than one may apply a) base pairing b) proofreading c) mismatch repair

all of them (base pairing, proofreading, mismatch repair)

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pair rules? a) A = G b) A + G = C + T c)A + T = G + C d)A = C

b) A + G = C + T

A student isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. After adding some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has the student probably left out of the mixture? a) DNA polymerase b) DNA ligase c) okazaki fragments d) primase

b) DNA ligase

Which of the following sequences in double-stranded DNA is most likely to be recognized as a cutting site for a restriction enzyme a) AAGG TTCC b) GGCC CCGG c) ACCA TGGT d) AAAA TTTTT

b) GGCC CCGG

why is it so important to be able to amplify DNA fragments when studying genes? a) DNA fragments are too small to use individually b) a gene may represent only a millionth of the cell's DNA c) restriction enzymes cut DNA into fragments that are too small d) a clone requires multiple copies of each gene per clone e) it is important to have multiple copies of DNA in the case of laboratory error

b) a gene may represent only a millionth of the cell's DNA

which of the following statements correctly describes chromatin? a) heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA b) both heterochromatin and euchromatin are found in the cytoplasm c) heterochromatin is highly condensed, whereas euchromatin is less compact d) euchromatin is not transcribed, whereas heterochromatin is transcribed

c) heterochromatin is highly condensed, whereas euchromatin is less compact

in a nucleosome, the DNA is wrapped around a) polymerase molecules b) ribosomes c) histones d) a thymine dimer

c) histones

which of the following helps to hold the DNA strands apart while they are being replication? a) primase b) ligase c) DNA polymerase d) single strand binding proteins e) nuclease

c) single strand binding proteins

In his work with pneumonia-causing bacteria and mice, Griffith found that a) the protein coat from pathogenic cells was able to transform nonpathogenic cells b) heat-killed pathogenic cells caused pneumonia c) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic d) the polysaccharide coat of bacteria caused pneumonia

c) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic

The elongation of the leading strand during DNA synthesis a) progresses away from the replication fork b) occurs in the 3'-5' direction c) produces Okazaki fragments d) depends on the action of DNA polymerase

d) depends on the action of DNA polymerase

imagine a bacterial cell with a mutation that renders DNA Pol I completely nonfunctional. what, precisely, would go wrong with replication in this cell? a) inability to unwind the double helix b) inability to prime replication c) inability to extend the length of leading and lagging strands d) inability to replace primers

d) inability to replace primers

e. coli cells grown on N15 medium are transferred to N14 medium and allowed to grow for two more generations. DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment? a) one high density and one low density band b) one intermediate density band c) one high density and one intermediate density band d) one low density and one intermediate density band

d) one low density and one intermediate density band

What does topoisomerase do?

relieves strain caused by unwinding of DNA