Chapter 5

Question 1

Describe Griffith’s contribution to the “DNA as genetic material” debate

Answer 1

Dead bacteria can transfer genetic information to live bacteria

Living R strain + Dead S strain = Living S strain

Question 2

Describe Avery/MacLeod/McCarty’s contribution to the “DNA as genetic material” debate

Answer 2

The material responsible for bacterial transformation is DNA

Fractionate S-strain cells into classes, only DNA could transform R strains

Question 3

Describe Hershey/Chase’s contribution to the “DNA as genetic material” debate

Answer 3

Genetic material of virus is DNA

Used T2 virus, labeled DNA with 32P and protein with 35S, infected bacteria only contained 32P

Question 4

What does the “denaturation” of DNA mean? How does it happen? Is it reversible?

Answer 4

The H-bonds between the strands of DNA will break down under high temperature or high pH

Cooler temperature or lower pH restores double helix

Question 5

What is the relationship between the sequence of DNA, its length, and the denaturing temperature? What is Tm?

Answer 5

Longer DNA and DNA with more G/C requires higher temperature

G/C has three H-bonds, A/T has two H-bonds

TM is the temperature at which half of the DNA has denatured

Question 6

What is “FISH”?

Answer 6

Fluorescent In Situ Hybridization, identification of sections of DNA with a probe (short piece of DNA labeled for detection with fluorescent dye or radioactivity

Question 7

What is “SKY”?

Answer 7

Spectral KarYotyping, use probes to label each chromosome as a different color

Question 8

Define karyotype

Answer 8

an ordered display of the full set of chromosomes of a cell arranged with respect to size, shape, and number

Question 9

Define centromere. How many does each chromosome have?

Answer 9

Centromeres allow duplicated chromosomes to be separated during M (mitosis) phase and can be seen as the constructed region of a mitotic chromosome. There are one per chromosome.

Question 10

Define replication origin. How many does each chromosome have?

Answer 10

The replication origin is where DNA replication is initiated. There are many per chromosome.

Question 11

Define telomere. How many does each chromosome have?

Answer 11

Telomeres are repetitive nucleotide sequences that cap the 2 ends of linear chromosomes and counteract the tendency of the chromosome to shorten with each round of replication.

Question 12

Define nucleolus

Answer 12

Large structure within the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled.

Question 13

Describe how DNA reaches the first level of organization

Answer 13

DNA Helix + 8 histone proteins → Nucleosomes with linker DNA

Question 14

Define nucleosome and nucleosome core particle

Answer 14

Nucleosome: Nucleosome core particles + segments of linker DNA (nucleosome+linker=200bp)

Nucleosome core particle: histone octomer + 150 bp of DNA around it

Question 15

How can histone interact with DNA?

Answer 15

It has a lot of positively charged amino acids that allow it to interact with the negative DNA

Question 16

How does nuclease interact with nucleosomes?

Answer 16

it digests linker DNA, but DNA on histones is protected

Question 17

Describe how DNA reaches the second level of organization

Answer 17

Nucleosomes + H1 proteins = 30 nm chromatin

Question 18

Where do H1 proteins bind?

Answer 18

on the outside of the nucleosome core particles

Question 19

Describe how DNA reaches the third step of organization

Answer 19

chromatin + condensin = looped DNA

Question 20

How do daughter cells know what kind of cells they are?

Answer 20

they inherit changes in their chromatin structure

Question 21

Describe the method of chromatin regulation involving proteins (as opposed to chemical groups)

Answer 21

Chromatin Remodeling Complexes

Local and temporary modification
Requires ATP to catalyse nucleosome sliding
Still 30 nm fiber, just changing relative position

Question 22

Describe the method of chromatin regulation involving chemical groups (as opposed to proteins)

Answer 22

Histone Tail Modification

Covalent addition of chemical groups
Combination of histone modification is called the histone code

Question 23

Define acetylation, give what catalyzes acetylation, and give what catalyzes deacetylation

Answer 23

Acetylation → loose packing and gene expression (overrules methylation)

histone acetyltransferases (HATs) and histone deacetylases (HDA)

Question 24

Define heterochromatin

Answer 24

a highly condensed region of an interphase chromosome; generally gene-poor and transcriptionally inactive. (random X sequence)

Question 25

Define euchromatin

Answer 25

one of the two main states in which chromatin exists within an interphase cell. Prevalent in gene-rich areas, its less compact structure allows access for proteins involved in transcription.

Question 26

Define methylation

Answer 26

heterochromatin formation and gene silencing