Chapter 13

Question 1

Chargaffs rules

How many hydrogen bonds form between base pairs

Answer 1

1. DNA base composition varies between species
2. Percentage of A=T and C=G

2 bonds with AT
3 bonds with CG

Question 2

Origin of replication

Answer 2

Site of start of replication; short stretches of DNA that have specific sequence of nucleotides. PROTEINS RECOGNIZE THE SEQUENCE AND ATTACH AND START

Question 3

Helicase

Answer 3

Enzyme that untwist the double helix at replication fork, separating the two strands

Question 4

SSBP

Answer 4

Bind to unpaired DNA strands, keeping them from re-pairing

Question 5

Topoisomerase

Answer 5

A protein that breaks, swivels and rejoins DNA strands to relive stress.

Question 6

Primase

Answer 6

An enzyme that joins RNA nucleotides to make a primer during DNA replication using the parental DNA strands as a template.

Question 7

DNA polymerase

Answer 7

Catalyze the synthesis of new DNA by adding nucleotides at the 3’ end of a pre existing strand

Question 8

Leading strand

Lagging strand

Answer 8

The new complementary strand synthesized continuously towards replication fork in 5’-3’ direction.

A disdcontinually synthesized DNA strand the elongates by means of Okazaki fragments in 5’-3’ away from replication fork.

Question 9

Okazaki fragments

Answer 9

Segments of 100-200 nucleotides long on lagging strand

Question 10

DNA ligase

Answer 10

A linking enzyme essential for DNA replication; catalyze the covalent bonding of the 3’ end of one DNA fragment to the 5’ end of another.

Question 11

Besides building what else does polymerase do?

Answer 11

Proof reads each nucleotide, if it’s wrong polymerase adds the correct one.

Question 12

Mismatch repair

Answer 12

Enzymes that remove and replace

Question 13

Nuclease

Answer 13

Enzyme that cuts DNA or RNA, either remaining one or a few bases or hydrolyzing DNA or RNA completely into its component nucleotides.

Question 14

Nucleotide excision repair

Answer 14

A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.

Question 15

Telomeres

Answer 15

Repetitive DNA at the end of a euk. Chromosome. These protect the genes from being eroded during successive rounds of replication.

Question 16

Nucleoid

Answer 16

A non-membrane- enclosed region Im a prok. Cell where its chromosomes are located.

Question 17

Heterochromatin

Answer 17

Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.

Question 18

Euchromatin

Answer 18

Less condensed form of Euk. Chromatin that is available for transcription.

Question 19

Histones

Answer 19

Small protein with a high proportion of positively charges amino acids that binds to the negatively charged DNA.

Question 20

Nucleosome

Answer 20

Basic unit of DNA packing

Question 21

Plasmids

Answer 21

Small circular DNA molecules that are replicated separately.

Question 22

Gene cloning

Answer 22

Production of multiple copies of a gene

Question 23

Polymerase chain reaction

Answer 23

Technique used for amplifying DNA in Vito by incubating it with specific primers, a heat resistant DNA polymerase and nucleotides.

Question 24

DNA sequencing

Answer 24

Determining the order of nucleotide bases in a gene or fragment.

Question 25

In bacteria where does the replication fork go

Answer 25

From both directions until it meets

Question 26

How many origins of replication do eukaryotic chromosomes have?

Answer 26

Hundreds

Question 27

Telomerase

Answer 27

Enzyme responsible for maintain of the length of telomeres by addition of guanine repetitive sequences