Genetics Exam #2

Front 1

Define replicon

Back 1

A DNA molecule or a region of DNA that repliates as an individual unit.

Front 2

Define autonomously replicating sequences (ARS)

Back 2

the sequences at which DNA replication can initiate.

Front 3

What starts initiation?

Back 3

A Primer (a short RNA molecule).

Front 4

What is elongation?

Back 4

nucleotide monomers added to the 3' end of the growing daughter strand.

Front 5

What is the leading strand?

Back 5

The continuously replicating strand.

Front 6

What is the lagging strand?

Back 6

has its 5' end facing the direction of unwinding, and the 5' strand cannot be elongated.

Front 7

What is proofreading?

Back 7

How the vast majority of the incorporation errors are corrected. Happens immediately after they occur.

Front 8

What is semi-conservative replication?

Back 8

The mechanism at which each parental DNA strand remains intact and serves as a template for a daughter strand.

Front 9

What is the replication fork?

Back 9

The region in which parental strands are separating and new strands are being synthesized. There can be either one or two.

Front 10

What is the terminus of replication?

Back 10

When there are two replication forks, the proceed in opposite directions from the origin and come together on the other side of the circle at a specific region.

Front 11

What is bidirectional replication?

Back 11

When replication is initiated at an origin of replication, two replication forks are created that move outward fro the origin.

Front 12

What is rolling-circle replication?

Back 12

Replication starts with a single-stranded cleavage at a specific sugar-phosphate bond in a double-stranded circle.

Front 13

What is the benefit of multiple initiation?

Back 13

reduces the total replication time of a large molecule.

Front 14

What is helicase?

Back 14

Unwinds the double helix to separate the parental strand. It is a protein that hydrolyzes ATP to drive the unwinding reaction.

Front 15

What is single stranded DNA-binding protein?

Back 15

The unwound strands of the double helix would tend to renature spontaneously, so they must be stabilized as single strands to serve as templates for DNA synthesis.

Front 16

What is gyrase?

Back 16

Cleaves both strands of a DNA duplex, swivels the ends of the broken strands to relieve the torsional stress and then rejoins the strands.

Front 17

What is primase?

Back 17

the RNA polymerase which produces the RNA primer.

Front 18

What is DNA helicase?

Back 18

Binds to DNA and travels 5' to 3' using ATP to separate strand and move the fork forward

Front 19

What are single-strand binding proteins?

Back 19

Keep parental strands open to act as templates

Front 20

What are Okazaki fragments?

Back 20

The short fragments in which the lagging strand is synthesized.

Front 21

What are the steps to connect the Ozaki fragments of the lagging strand?

Back 21

1. Removal of the RNA primer
2. Replacement of the primer with a DNA sequence.
2. Joining where adjacent DNA fragments come into contact.

Front 22

What are Holliday junctions?

Back 22

Where strands have exchanged pairing partners.
When Holliday junctions are broken, crossover occurs.

Front 23

What is mismatch repair?

Back 23

A correction mechanism that looks for mismatched basepairs.

Front 24

What is the double-stranded break and repair modeL?

Back 24

Recombination between DNA strands is intiated by a double-stranded break in a DNA duplex. The size of the gap is usually increased by nuclease digestion of the broken ends.

Front 25

What is the D-loop?

Back 25

The loop formed when part of a DNA strand is dislodged from a duplex molecule because of the partner strand's pairing with another molecule.

Front 26

What is the Holliday junction-resolving enzyme

Back 26

An enzyme that breaks and rejoins the Holliday junctions.

Front 27

What is the C-Value paradox?

Back 27

The genome size often differs enormously among species with the same level of metabolic, developmental, and behavioral complexity. There is a lack of correlation.

Front 28

Explain supercoiled.

Back 28

Segments of the double-stranded DNA are twisted around one another.

Front 29

What is DNA topoisomerase?

Back 29

What produces the supercoiling of natural DNA moleculs

Front 30

What is DNA toposomerase I?

Back 30

Acts by wrapping themselves completely around a DNA duplex and causing a single-stranded nick by breaking a phosphodiester bond in the backbone of one of the DNA strands.

Front 31

What is DNA topoisomerase II?

Back 31

Produces a double-stranded gap in one molecule through which another double-stranded molecule is passed.

Front 32

What are histones?

Back 32

Largely responsible for the structure of the chromatin.
H1
H2A
H2B
H3
H4

Front 33

What are the three major components of Eukaryote DNA?

Back 33

Unique sequences
Highly repetitive sequences
Middle repetitive sequences

Front 34

What is heterochromatin?

Back 34

Highly repetitive
Lovated near centromeres and telomeres
Not transcribed much

Front 35

What is euchromatin?

Back 35

Most of DNA
actually have genes
"Active DNA"

Front 36

What are telomeres?

Back 36

A series of repeat sequenes within DNA and special proteins
Telomeres at the 3' end does not have a complementary strand and is called a 3' overhang.
Non-coding DNA that can get eroded without affecting gene expression.

Front 37

Linkage

Back 37

Genes that are always transmitted together are said to show compete linkage.

Front 38

Recombinant Types of Chromosomes

Back 38

Daughter chromosomes that carry combinations of alleles not present in the parental chromosomes.