Chapter 14. DNA: The Genetic Material

In trying to discover the substance responsible for transformation, Avery MacLeod, and McCarty removed __________ from their preparation and found that transforming activity persisted.

protein

A __________ __________ is the partial opening of a DNA helix to form two single strands.

replication fork

Interpretation of the Meselson Stahl data leads to support of this model DNA replication

semiconservative

DNA replication in E. coli ends at a site called the __________

terminus

In nucleic acids, the prime symbol is used to indicate

the carbon i a sugar rather than the atoms in the the bases attached to the sugars

Chargaff's experiments showed that the amount of adenine in a sample was always the same as the amount of

thymine

In a DNA double helix with 23% adenine, you would expect to also see 23%

thymine

During DNA replication, how many strands of DNA are used as templates to synthesize new strands?

2

How many hydrogen bonds are formed between adenine and thymine in the DNA helix?

2

Which of these best describes the density of the bacterial DNA after the second round of replication in the Meselson-Stahl experiments?

2 density classes - one intermediate and one 14N

How many hydrogen bonds form between cytosine and guanine in the DNA double helix?

3

A DNA strand runs 3' to 5'. The complementary strands runs

5' to 3'

Once synthesis has begun, DNA can only be synthesized in this direction

5' to 3'

The sequence of DNA bases is written in the __________' to __________' direction

5':3'

Which of these is not involved in the unwinding of DNA during replication?

RNA polymerase (makes primers)

E. coli polymerases I, II, and III have 3' to 5' __________ activity, which provides them with a proofreading function, i.e. they can remove a mispaired base.

exonuclease

DNA'S phosphodiester __________ is composed of sugars and phosphates.

backbone

This model for DNA replication suggests that both strands of the double helix remain intact and the new DNA double helix consists of two new DNA strands

conservative

Different models for DNA replication included

conservative replication, semiconservative replication, dispersive replication

Match the following strands with the type of synthesis

leading strand- synthesized continuously lagging strand- synthesized in small fragments that are later connected

A heavy isotope of nitrogen was used in the Meselson-Stahl experiment so that

different DNA molecules could be separated via ultracentrifugation.

This model of DNA replication suggests that newly synthesized strands of DNA have mixtures of parental and newly synthesized strands of DNA.

dispersive

The level of DNA that resembles a spiral staircase is the

double helix

In an aging cell the activity of the telomerase would be

low

DNA primate (choose all that apply)

makes a primer of RNA complimentary to the DNA., makes a primer about 10-20 nucleotides in length.

The ____________ of replication in a site within a chromosome where DNA replication begins.

origin

The polarity of a DNA or RNA strands refers to the orientation of which of the following?

phosphate group to hydroxyl group

Adjacent nucleotides in the same DNA strand are held together by covalent bonds known as __________ bonds

phosphodiester

This DNA enzyme covalently links nucleotides together

polymerase

Replication of this type begins at a single origin of replication

prokaryotic

The function of telomeres is to

protect the ends of chromosomes

Chromosomes are primarily composed of DNA and __________

protein

Which of these are part of the Watson-Crick Model?

-Each DNA molecule is composed of two strands that run antiparallel. -Each DNA molecule is composed of 2 phosphodiester strands.

Select all of the following that are components of a nucleotide.

-sugar -phosphate group -nitrogenous base

Indicate the 4 nitrogenous bases used in DNA.

-thymine -adenine -guanine -cytosine

Place the steps of lagging strand synthesis in the correct order (start at the top):

1. Synthesize primers using primate 2. Synthesize DNA 3. Replace RNA primers with DNA 4. Seal nicks in the DNA

During the synthesis of the lagging DNA strand, Okazaki fragments are joined by the enzyme

DNA ligase

The tetra nucleotide hypothesis suggested that

DNA was a repeat of a four base sequence that never varied

Which types of cells have more than one origin of replication?

Eukaryotes

Which of the following was not a piece of evidence provided by the Avery, MacLeod, and McCarty experiments to suggest that DNA is the transforming substance?

Extracting proteins and lipids reduced transforming activity

In which of the following chromosomal entities are an individual's traits specified?

Genes

Match these enzymes involved in DNA replication with their function

Helicase- uses ATP to unwind DNA strands Topoisomerase- relieves strain caused by unwinding and prevents supercoiling Primase- synthesized 10-12 bp RNA sequences that function as primers Polymerase- synthesizes new DNA strand by attaching nucleotides to 3'' end of the DNA strand

This polymerase uses 5' to 3' exonuclease activity to remove primer segments and its' 5' to 3' polymerase activity to replace them.

I

Which of these is not required for DNA replication?

Lipids

The discovery of a substance called nuclein, later to be named nucleic acid, was accomplished by

Miescher

Short fragments of DNA created on the lagging strand of DNA during replication are called

Okazaki fragments

Chargaff's rule indicates that the amount of A in a sample is equal to the amount of __________ and the amount of C is an sample is equal to the amount of __________

T:G

In base pairing between complimentary strands of DNA, A pairs with __________ and C pairs with __________

T:G

In bacterium, where does termination of replication occur, relative to the origin?

The termination site is opposite to the origin

What class of enzymes relieve torsional strain in DNA strands of the replication fork?

Topoisomerases

Miescher's nucleic was later termed nucleic acid because it was

found in the nucleus, slightly acidic

The enzyme DNA _________ is topoisomerase involved in DNA replication

gyrate

The __________ enzyme uses ATP to unwind the DNA template

helicase

The sliding clamp of DNA polymerase

holds the polymerase to the DNA template

The primary purpose of the Meselson and Stahl experiments was to determine

how DNA replicates

List several differences in prokaryotic and eukaryotic replication.

structure of chromosome (linear vs. circular), complexity of enzymology, number of origins of replication

Cancerous cells generally show continued activation of the enzyme __________ which allows them to maintain telomere length.

telomerase