Chapter 16 The Molecular Basis Of Inheritance

Question 1

Who introduced an elegant double-helical model for the structure of deoxyribonucleic acid?

Answer 1

James Watson and Francis Crick

In 1953

Question 2

Substance of inheritance?

Answer 2

DNA

Question 3

Morgan’s group showed that genes are located on chromosomes

What become candidates for the possible genetic material?

Answer 3

DNA and protein

Question 4

The role of DNA in heredity was first discovered by studying….

Answer 4

Bacteria and the viruses that infect them

Question 5

The discovery of the genetic role of DNA began with research by ….

Answer 5

Fredrick Griffith in 1928

Question 6

When Griffith mixed heat-killed remains of the pathogenic strain with living cells of the harmless strain….. what happened?

Answer 6

Some of the living harmless strains become pathogenic

This is called transformation*

Question 7

When there is a change in phenotype and genotype due to assimilation of foreign DNA

Answer 7

Transformation

Question 8

Who announced the transforming substance was DNA?

Answer 8

Oswald Avery, Maclyn McCarty, and Colin MacLeod

Question 9

More evidence of DNA as the genetic material came from studies of…..

Answer 9

A virus that infects bacteria

These are called bacteriophages or phases

Question 10

A virus that infects bacteria is called?

Answer 10

Bacteriophages or phages

They are widely used in genetics research

Question 11

Who proved that one of the two components of T2 (DNA or protein) enters an E. coli cell during infection?

Answer 11

Alfred Hershey and Martha Chase

Question 12

What are Charagaff’s rules?

Answer 12

Base pairings are different among species

The amount of and ratio of base pairings is equal

Question 13

Who used X-Ray crystallography to study the molecular structure of DNA?

Who produced the image of the DNA molecule using this technique?

Answer 13

Maurice Wilkins and Rosalind Franklin

Franklin

Question 14

Franklins X-Ray crystallography images of DNA enabled _________ to deduce the width of helix and the spacing of the nitrogenous bases

The width suggested that the DNA molecule was made up of two stands, forming a double helix

Answer 14

Watson

Question 15

What is the backbone of DNA?

Answer 15

Sugar phosphate backbone

Question 16

Bases are on the _____ of DNA?

Answer 16

Inside

Question 17

DNA is stabilized by?

Answer 17

Hydrogen bonds

Question 18

What are the three components of DNA?

Answer 18

Nitrogenous base (purines or pyrimidines)

Phosphate group

Pentose sugar (deoxyribose)

Question 19

In DNA replication, the parent molecule unwinds, and _________ daughter strands are built based on base pairing rules

Answer 19

Two new

Question 20

What were the three alternative models of DNA replication?

Answer 20

Semi-conservative (this one is correct)

Conservative

Dispersive

Question 21

Who’s experiment supported the semi conservative model?

Answer 21

Meselson and Stahl

Question 22

Explain Meselson and Stahls model for replication.

Answer 22

Old nucleotides labels with a heavy isotope of nitrogen, while any new nucleotides were labeled with a lighter isotope

First replication produced a band of hybrid DNA, eliminating the conservative model

The second replication produced both light and hybrid DNA, eliminating the dispersive model

Question 23

Backbone of nucleotides?

Answer 23

Nitrogen

Question 24

Replication begins at special sites called _______________, where the two DNA strands are separated, opening up a replication “bubble”

Answer 24

Origins of replication

Question 25

How many sites of origin may a eukaryotic chromosomes have?

Answer 25

Hundreds or even thousands

Question 26

Replication proceeds in what direction from each origin?

Answer 26

Both directions

Question 27

At the end of each replication bubble is a .....

Answer 27

Replication fork, a Y-shaped region where new DNA strands are elongating

Question 28

Are enzymes that untwist the double helix at the replication forks Unzips or breaks hydrogen bonds

Answer 28

Helicases

Question 29

Binds to and stabilizes single-stranded DNA until it can be used as a template This prevents Two stands from coming back together

Answer 29

Single-strand binding protein

Question 30

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

Answer 30

Topoisomerase

Question 31

- catalyze the elongation of new DNA at a replication fork - nucleoside triphosphate added to a growing DNA strand - the rate of elongation is about 500 nucleotides per second in bacteria and 50 per second in human cells

Answer 31

DNA polymerase

Question 32

- adds nucleotides * always elongates in a 5’ to 3’ direction because of the OH group - for the enzyme to work it must be able to bond to OH

Answer 32

DNA polymerase

Question 33

DNA polymerases add nucleotides only to the free _____ end of a growing strand; therefore, a new DNA strand can elongate only in a ____ to ____ direction

Answer 33

3’ 5’, 3’

Question 34

DNA ploymerases cannot initiate synthesis of a ploynucleotide; they can only add nucleotides to the ____ end

Answer 34

3’

Question 35

The initial nucleotide strand is a short one called an....

Answer 35

RNA or DNA primer

Question 36

An enzyme called ___________can start an RNA chain from scratch

Answer 36

Primase

Question 37

How many primers are needed to synthesis the leading strand?

Answer 37

Only one

Question 38

Most _____________ require a primer and a DNA template strand Catalyze the elongation of new DNA at a replication fork

Answer 38

DNA polymerase

Question 39

This adds RNA, DNA replication starts this way Initiated by an RNA primer 5’ ——-> 3’ direction

Answer 39

Primase

Question 40

DNA polymerase dose not start DNA replication. What does?

Answer 40

Primase

Question 41

Can synthesis a complementary strand continuously, moving away from the replication fork In a 5’ to 3’ direction

Answer 41

DNA polymerase

Question 42

________

Answer 42

DNA polymerase 3

Question 43

Synthesized as a series of segments in the lagging strand called ....

Answer 43

Okazaki fragments

Question 44

- removes RNA primer from leading and lagging strand | - replaces primer with DNA

Answer 44

DNA polymerase 1

Question 45

Joins okazarki fragments together

Answer 45

DNA ligase

Question 46

__________ untwists the double helix and separates the template DNA at the replication fork

Answer 46

Helicase

Question 47

Binds to and stabilizes single stranded DNA u til it can be used as a template

Answer 47

Single-stranded binding protein

Question 48

Corrects “overwinding” ahead of replication forks by breaking, swiveling and rejoining DNA strands

Answer 48

Topoisomerase

Question 49

DNA polymerase removes ______ and replaces it with ______

Answer 49

RNA, DNA

Question 50

_________ Synthesizes an RNA primer at the 5’ ends of the leading strand and the Okazaki fragments

Answer 50

Primase

Question 51

_________________ continuously synthesizes the leading strand and elongates Okazaki fragments

Answer 51

DNA pol 3

Question 52

_________ removes primer from the five prime end of the leading strand and Okazaki fragments, replacing primer with DNA and adding to adjacent three prime end

Answer 52

DNA pol 1

Question 53

___________ Joins the three prime end of the DNA that replaces the primer to the rest of the leading strand and also joins the lagging strand fragments

Answer 53

DNA ligase

Question 54

When exposed to UV light, T=T can happen. How is it repaired and what is it called?

Answer 54

Mismatch repair | Polymerase will remove the damage

Question 55

The DNA replication machine is probably ____________ during the replication process Recent studies support a model in which DNA polymerase molecules “real in” parental DNA and “extrude” newly made daughter DNA molecules

Answer 55

Stationary

Question 56

Enzymes cut out and replace damaged stretches of DNA

Answer 56

Nucleotide excision repair

Question 57

_____________ proofreads newly made DNA, replacing any incorrect nucleotides In mismatch repair of DNA, repair enzymes correct errors in base pairing

Answer 57

DNA polymerase

Question 58

The ends of chromosomes are called?

Answer 58

Telomeres

Question 59

Limitations of DNA polymerase create problems for the linear DNA of eukaryotic chromosomes The usual replication machinery provides no way to complete the five prime ends, so repeated rounds of replication produce....

Answer 59

Shorter DNA molecules

Question 60

_______________ do not prevent the shortening of DNA molecules, but they do postpone the erosion of genes near the ends of DNA molecules

Answer 60

Telomeres

Question 61

An enzyme called _________ catalyzes the lengthening of telomeres in germ cells

Answer 61

Telomerase It extends, and fills in gaps This reduces as an organism ages

Question 62

99% of all types of human cancers have high levels of _____________

Answer 62

Telomerase

Question 63

Discrete unit of genetic material | And It is composed of _______

Answer 63

Chromosomes Chromatin- DNA-protein complex

Question 64

What are the three levels of DNA compaction?

Answer 64

1. DNA wrapping 2. 30-nm fiber 3. Radial loop domains

Question 65

DNA wrapped around histones to form _________

Answer 65

Nucleosomes

Question 66

DNA wrapping shortest length of DNA molecule _________

Answer 66

7-fold

Question 67

Current model suggests asymmetric, 3-D zigzag of nucleosome’s Shortens length another sevenfold

Answer 67

30-nm fiber

Question 68

- interaction between 30 nm fibers and nuclear matrix - each chromosome located in discrete territory - levels of compaction of chromosomes not uniform (hetrochromatin, euchromatin)

Answer 68

Radial loop domains

Question 69

When cells prepare to divide, chromosomes become....

Answer 69

Even more compacted

Question 70

When chromosomes are not as compact (this is when they are being used)

Answer 70

Euchromatin

Question 71

When chromosomes are much more compact (off/not being used) Metaphase chromosomes highly compacted

Answer 71

Hetrochromatin