exam 2 info

Question 1

what is a packaging mechanism for chromosomes

Answer 1

chromatin

Question 2

what are chromosomes

Answer 2

stretches of compressed DNA

Question 3

whats chromatin

Answer 3

specific proteins interacting with DNA to form nucleoprotein

Question 4

about how long is human DNA in meters

Answer 4

2 meters (6’6”)

Question 5

how is the nucleoid formed?

Answer 5

specific proteins interact with DNA

Question 6

what kind of fold compact is DNA in a nucleus

Answer 6

10,000 fold compaction

Question 7

what are histones

Answer 7

small basic proteins

Question 8

how would histones be viewed under microscopy

Answer 8

beads on a string. the beads being nucleosome

Question 9

what is the nucleosome

Answer 9

basic unit of eukaryotic chromatin, formed from about 8 histones wrapped by DNA

Question 10

what is chromatin remodeling

Answer 10

enzymes that use ATP to alter chromatin structure

Question 11

what 3 mechanisms are site exposure models

Answer 11

repositioning
ejection
unwrapping

Question 12

what 2 mechanisms are altered composition

Answer 12

dimer exchange

dimer ejection

Question 13

closed chromatin prevents what

Answer 13

prevents proteins to bind to DNA

Question 14

open chromatin allows what

Answer 14

provides access to specific DNA sequences

Question 15

what is going on if a a chromatin is depleted of nucleosomes

Answer 15

have active regions of the genome

Question 16

what goes on during nuclease digestion

Answer 16

digestion removes linker DNA between nucleosomes and destroys it with MNase

Question 17

what is endonuclease activity

Answer 17

cleavage of DNA

Question 18

what is exonuclease activity

Answer 18

chewing of DNA

Question 19

how many bases of DNA typically wrap around nucleosomes

Answer 19

150

Question 20

what is a centromere

Answer 20

section of chromosomes responsible for cell’s ability to properly segregate sister chromatids during cell division

Question 21

how are nucleosomes arranged in chromatid

Answer 21

biologists don’t really know

Question 22

why is chromatin modification important

Answer 22

recruits proteins to chromatin an regulating chromatin-based processes

Question 23

how are proteins modified

Answer 23

through covalent attachments of various functional groups to specific amino acids

Question 24

what can be attached to a proteins during modification

Answer 24

small chemical groups
lipids
small polypeptides

Question 25

what occurs during proteolysis

Answer 25

split of an inactive precursor protein into an active form

Question 26

what types of protein modifications are there

Answer 26

acetylation methylation phosphorylation

Question 27

what are nucleosomes

Answer 27

8 histones proteins wrapped by about 147 base pairs

Question 28

how are histones bonded

Answer 28

covalently

Question 29

nomenclature structure of histones

Answer 29

name of histone + residue one letter code + residue number + modification

Question 30

histone lysine is acetylated by

Answer 30

acetyltransferases

Question 31

histone lysine is deacetylated by

Answer 31

deacetylases

Question 32

what occurs during acetylation of histone lysine

Answer 32

neutralizes the postitive charge of lysine's side chain

Question 33

when does lysine acetylation also occur

Answer 33

in citric acid cycle

Question 34

functions of protein lysine acetylation

Answer 34

``` regulate interactions of histones with DNA changes interaction partners changes cellular localization controls cytoskeleton dynamics controls cell growth ```

Question 35

histone lysine is catalyzed by? and removed by?

Answer 35

catalyzed- methyltransferases | removed- demethylases

Question 36

lysine can have how many methyl groups

Answer 36

up to 3, and doesn't ever change the charge

Question 37

whats the purpose of histone lysine methylation

Answer 37

creates binding sites for many proteins (ex: polycomb)

Question 38

what are hox genes and their purpose

Answer 38

organized linear structures that specify the body plan in multicellular organisms. They must be expressed in the correct environments and silenced everywhere else for proper development

Question 39

mutations in the polycomb gene result in

Answer 39

ectopic (abnormal location) sex combs

Question 40

what are ectopic sex combs

Answer 40

a gene is not correctly placed, causing sex spots (on legs) in places they shouldn't be

Question 41

what is a homeotic phenotype

Answer 41

mutational phenomenon of homeostasis, where an organ turns into another

Question 42

mutations in the trihorax gene results in

Answer 42

sex combs are significantly reduced

Question 43

whats the function of the polycomb-group protein

Answer 43

repress gene expression (transcription) through chromatin based mechanism

Question 44

what is Zeste (E(z))?

Answer 44

its a polycomb-group protein enhancer, that catalyzes H3K27me3, through methylation

Question 45

function of Trithorax-group proteins

Answer 45

activate gene expression

Question 46

what does Trithorax do and catalyze?

Answer 46

its a histone methyltransferase, that catalyzes H3K4me3 and H3K27