Chapter 9: Replication

Which enzyme catalyzes the formation of covalent bonds between adjacent DNA fragments to complete the replication process?

Ligase

During DNA synthesis, the sites where the two template strands are unwound and new DNA is made are called what?

Replication forks

Which enzyme is responsible for removing the RNA primers?

DNA polymerase I

In Escherichia coli, what is the main enzyme that adds DNA nucleotides during DNA replication?

DNA polymerase III

The three proposed mechanisms for DNA replication are presented in this figure: A shows the ______ model; B shows the ________ model; and C shows the ______ model.

semiconservative conservative dispersive

During DNA replication, the parental DNA strand can also be called a(n) _______ strand, because it is used for the synthesis of a daughter strand of DNA.

template

The DNA strands that can be copied to produce new DNA strands are called the ______.

templates

Assuming DNA replication had been conservative, Meselson and Stahl would have observed what bands in the centrifuge tube after one round of replication?

Two bands: one heavy and one light

The lagging strand is made:

discontinuously in the opposite direction of the replication fork

The difference between euchromatin and heterochromatin relates to the:

compaction level of the molecule.

DNA replication relies on the ______ of DNA strands according to the _____ rule.

complementarity; AT/GC

When cells prepare to divide, the chromosomes become ______ to aid in proper alignment.

condensed

Heterochromatin involves a tighter packing of loops as compared to

euchromatin

During replication, the enzyme DNA _______ uses energy from ATP to separate the two strands. This generates additional coiling ahead of the replication fork that is alleviated by another enzyme called DNA ________.

helicase topoisomerase

DNA is compacted by wrapping itself around a group of proteins called ______.

histones

The group of proteins that DNA wraps around to compact itself and to form nucleosomes is called ________.

histones

A typical eukaryotic chromosome may be _____ of millions of base pairs long.

hundreds

DNA polymerase III:

is the major replication enzyme.

In DNA replication, the ______ strand is made discontinuously in the direction opposite to the movement of the replication fork.

lagging

During DNA replication, the _______ strand is synthesized continuously while the _________ strand is synthesized as small fragments that are connected to each other to form a continuous strand.

leading lagging

The replication process is completed when the enzyme DNA ______ forms a covalent bond between adjacent DNA fragments.

ligase

A metaphase chromosome is ______ a chromosome in a non-dividing cell.

more condensed than

Relative to a prokaryotic chromosomes, eukaryotic chromosomes are:

much larger.

Meselson and Stahl used two isotopes of the element _______ in their DNA replication experiments, so that the daughter strands could be distinguished from the parental strands.

nitrogen

Match the mechanism of DNA replication with its correct illustration.

A : semiconservative B : conservative C : dispersive

In order to complete synthesis of the Okazaki fragments on the lagging strand, the following must occur. Place these items in the correct order. Start with the earliest on top.

1. Removal of RNA primers 2. synthesis of DNA in area where the primers have been removed 3. covalent joining of adjacent fragments of DNA

A Meselson-Stahl experiment is performed on a bacterial culture. What percentage of DNA molecules is expected to be of intermediate density after three rounds of replication?

25%

Once synthesis has begun, DNA can only be synthesized in a ______ direction.

5' to 3'

Which of the following processes proceeds according to the AT/GC rule?

DNA replication

Chromatin makes up eukaryotic chromosomes and is a complex of:

DNA. proteins.

The model organism used by Meselson and Stahl was _____

Escherichia coli

Match the proteins involved in DNA replication with their function.

Helicase : Causes DNA strand separation at the replication fork Topoisomerase : Relieves coiling in DNA strands ahead of the replication fork Single-strand binding protein : Prevents the two DNA template strands from re-forming the double helix

Which are enzymatic features of DNA polymerase?

It can only synthesize DNA in the 5' to 3' direction. It is unable to begin DNA synthesis on a bare template strand.

Which of the following statements about DNA replication is TRUE?

The leading strand is synthesized continuously while the lagging strand is synthesized in a series of small fragments that are later connected.

DNA replication is described as ______ because DNA replication proceeds outward from two replication forks.

bidirectional

The term ______ refers to DNA replication proceeding outward from two replication forks.

bidirectional

The DNA-protein complex that makes up eukaryotic chromosomes is called _____

chromatin

An RNA _________ is required to produce each Okazaki fragment in Escherichia coli.

primer

DNA polymerase I ______ RNA primers in the ______ direction.

removes; 5' to 3'

DNA replication proceeds outward from two ______ _____ , which are the sites where the template strands are unwound and new DNA is synthesized.

replication forks