Chapter 16: The Molecular Basis Of Inheritance

Question 1

Structure of DNA

Answer 1

Double helix

Antiparallel

Question 2

Chargaff’s Rules

Answer 2

DNA composition varies between species

For each species percentages of A/T are roughly equal as are the C and G bases

Question 3

DNA Composition

Answer 3

Deoxyribose - 5 carbon sugar
Nitrogenous base
Phosphorus group
Complimentary nucleotides are held together by hydrogen bonds

Question 4

Bacteriophage

Answer 4

A virus that infects bacteria.

Infects genetic material into a cell that turns it into a phage producing factory

Question 5

Evidence that DNA is the genetic material

Answer 5

Radioactive sulfur was added to proteins and radioactive phosphorus was added to the DNA in the chromatin of a phage

Only the phosphorus was transferred to the daughter phages

Question 6

Chromatin

Answer 6

The complex of DNA and proteins that makes up eukaryotic chromosomes.

When the cell is not dividing it exists in its dispersed form, as a mass of long, thin fibers that are not visible with a light microscope

Question 7

Euchromatin

Answer 7

The less condensed form of eukaryotic chromatin that is available for transcription

Question 8

Heterochromatin

Answer 8

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

Question 9

Replication Fork

Answer 9

A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and the new strands are being synthesized

Question 10

Helicase

Answer 10

Unwinds parental double helix at replication fork

Question 11

Single-strand binding protein

Answer 11

Binds to and stabilizes single-stranded DNA until it is used as a template

Question 12

topoisomerase

Answer 12

Relieves overwinding strain ahead of replication fork by breaking, swiveling, and rejoining DNA strands

Question 13

DNA pol I

Answer 13

Removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides added to the e’ end of the adjacent fragment

Question 14

DNA pol II

Answer 14

Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or pre-existing DNA strand.

Question 15

Okazaki Fragment

Answer 15

A short segment of DNA synthesized away Fromm the replication fork on a template strand during DNA replication

Question 16

DNA ligand

Answer 16

Joins Okazaki fragment of lagging strand

On leading strand, joins 3rd end of DNA that replaces primer to rest of leading strand DNA

Question 17

Telomere

Answer 17

Tandemly repetitive DNA at the end of eukaryotic chromosome’s DNA molecule. Telomeres protect the organism’s genes from being eroded during successive rounds of replication

Question 18

Telomerase

Answer 18

Catalyzes the lengthening of telomeres in eukaryotic germ cells, thus restoring their original length

Question 19

Leading Strand

Answer 19

The new complementary DNA strand synthesized continuously along the template strand towards the replication fork in the 5 to 3 direction

Question 20

Lagging strand

Answer 20

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5 to 3 direction away from the replication fork.

Question 21

Semiconservative model

Answer 21

A type of DNA replication in which the replicated double helix consists of one old strand, derived from the parent molecule, and one newly made strand.