Chapter 18

Question 1

What is the structure of the purines

Answer 1

double-ring

A and G

Question 2

What is the structure of the pyrimidines

Answer 2

Single ring

T and C

Question 3

What did Chargaff discover

Answer 3

DNA from different cells have the same percentage of each of the four bases

Question 4

Percentages of bases do not vary with…

Answer 4

tissues age, within an individual, nutritional state, and environment

Question 5

Where does the DNA vary

Answer 5

Species to species

closely related species have similar compositions

Question 6

What was Chargaff’s most important discovery about DNA base amounts

Answer 6

A=T
G=C
A+G=C+T

Question 7

What is Watson and Crick’s DNA model

Answer 7

Double-helix

polymer with a backbone of repeating sugars and phosphate groups

Question 8

what is the diameter of the helix

Answer 8

2nm

Question 9

What holds together the purine-pyrimidine pairs

Answer 9

Hydrogen bonds

Question 10

What is significant about the Hydrogen bonds versus the covalent bonds holding the backbone together

Answer 10

The hydrogen bonds can easily be broken for things like replication while leaving the nucleotides intact

Question 11

How many nucleotides per turn

Answer 11

10

Question 12

DNA denaturation

Answer 12

The DNA splitting apart which can be induced experimentally with heat

Question 13

DNA renaturation

Answer 13

the reverse of denaturation where you lower the temp and the DNA comes back together

Question 14

What determines the melting temperature of DNA

Answer 14

Base composition (GC bases increase temp) and proper pairing (increases temp)

Question 15

Why do GC base pairs take longer to melt

Answer 15

because they are held together by 3 H bonds rather than the 2 H bonds that hold AT together

Question 16

Genome

Answer 16

the DNA that contains one complete copy of genetic information

Question 17

What is B-DNA

Answer 17

Right hand helix

main form of DNA

Question 18

What is Z-DNA

Answer 18

left hand helix

zig-zag pattern of backbone

Question 19

What is the function of Z-DNA

Answer 19

process by which some genes are expressed

Question 20

What is the major groove generally the site for

Answer 20

direct info readout

Question 21

What is the minor groove important for

Answer 21

target for a few regulatory and structural proteins

Question 22

What is the nucleoid

Answer 22

region where the bacterial chromosome resides

Question 23

what is the deal with the bacterial nucleoid

Answer 23

they have super long DNA that is somehow packaged into a tiny space and scientists still aren’t sure how they do it

Question 24

Histones

Answer 24

group of proteins with strong positive charge

Question 25

What charge does DNA have

Answer 25

negative

Question 26

what is chromatin

Answer 26

DNA packaged together with proteins

Question 27

Nucleosome

Answer 27

proteins are clustered at 2 bp intervals along the DNA molecule in chromatin fibers (beads on a string)

Question 28

what is nuclease

Answer 28

enzyme that chops up nucleotides

Question 29

what is nucleosome structure

Answer 29

8 histone molecules and the core with DNA wrapped around the histones (146 bp DNA makes 2 wraps around core)

Question 30

What are the levels of chromatin packing from smallest to largest

Answer 30

nucleosomes, fibers, looped domains, hectochromatin, highly condensed (chromosomes)

Question 31

what are fibers

Answer 31

30nm chromatin fibers made of coiled nucleosomes

Question 32

what are looped domains attached to

Answer 32

attached to scaffolding proteins

Question 33

what is the difference between hectochromatin and euchromatin

Answer 33

hecto is more tightly packed and usually not active. It shows up as dark spots in micrographs

Question 34

What kind of DNA is not present in high amounts in mitochondrial DNA

Answer 34

Non-coding DNA

Question 35

What are two ways mitochondrial and plastid DNA is more similar to bacterial DNA

Answer 35

Circular DNA and no histones

Question 36

If every cell contains the genes for every protein in the body, how come we don't make insulin in our elbows

Answer 36

the nucleus plays a role in controlling gene expression

Question 37

What is the basic composition of the nuclear envelope

Answer 37

composed of two membranes and nuclear pores

Question 38

outer membrane of nuclear envelope

Answer 38

continuous with rough ER

Question 39

inner membrane of nuclear envelope

Answer 39

chromatin is stuck to it

Question 40

perinuclear space

Answer 40

the space in between the membranes of the nuclear envelope

Question 41

how are nuclear pores composed

Answer 41

elaborate structure of about 100 proteins | octagonal arrangement

Question 42

what can pass through nuclear pores

Answer 42

small water soluble molecules pass unimpeded | larger molecules can pass with approval

Question 43

What are transporters

Answer 43

help move molecules out of nuclear pores

Question 44

what things can be moved out by transporters

Answer 44

completed mRNA, assembled ribosomal subunits

Question 45

What things are required for import through nuclear pores

Answer 45

nuclear localization signal, importin, GTP hydrolysis

Question 46

What things are required for a molecule to be exported through a pore

Answer 46

Nuclear export signal, exportin, GTP

Question 47

What is the nuclear localization signal/nuclear export signal

Answer 47

structure on molecule that is binding site for importin/exportin

Question 48

What are two primary functions of the nucleus

Answer 48

RNA synthesis and ribosomal subunit synthesis

Question 49

What is the nucleolus organizer region

Answer 49

region where the nucleoli form

Question 50

what is the NOR comprised of

Answer 50

stretch of DNA where multiple copies of the gene for rRNA are located

Question 51

what is created at the site where all the ends of chromosomes with NOR cluster together

Answer 51

the nucleolus