Nucleus

Question 1

eukaryote etymology

Answer 1

“true kernel”

Question 2

main defining feature of eukaryote cells

Answer 2

a nucleus

Question 3

what percentage of the nucleus volume is the membrane

Answer 3

1%

Question 4

what percentage of the cell’s volume is enclosed within the nuclear membrane

Answer 4

6%

Question 5

2 parts of the nuclear membrane

Answer 5

1. inner nuclear envelope

2. outer nuclear envelope

Question 6

between inner and outer nuclear envelopes

Answer 6

perinuclear space

Question 7

nuclear lamina

Answer 7

intermediate filaments (polymers) made with nuclear lamins (monomers)

Question 8

where is the nuclear lamina found

Answer 8

right inside of the nuclear membrane

Question 9

chromatin

Answer 9

DNA and proteins of interphase chromosomes

Question 10

euchromatin

Answer 10

location of mRNA and tRNA genes

Question 11

heterochromatin

Answer 11

centromere DNA in storage

Question 12

nucleolus

Answer 12

location of rRNA genes and assembly of ribosomal subunits

Question 13

how big are nuclear pores

Answer 13

composed of 50-100 different proteins and ~120 nm in diameter

Question 14

how many nuclear pores are in a typical mammalian cell?

Answer 14

~3000

Question 15

7 things that are imported into the nucleus

Answer 15

1. nucleotides
2. RNA pols
3. spliceosomes
4. transcription factors
5. DNA pols
6. histones
7. cdk/cyclin proteins

Question 16

3 things that are exported from the nucleus

Answer 16

1. mRNAs
2. tRNAs
3. ribosomal subunits

Question 17

how do small molecules enter the nucleus

Answer 17

diffusion through nuclear pores

Question 18

how do large molecules enter the nucleus

Answer 18

active transport attached to proteins

Question 19

are nuclear pores 1-way or 2-way transport

Answer 19

2-way

Question 20

what is required for nuclear import

Answer 20

nuclear localization signal (NLS)

Question 21

NLS

Answer 21

AA sequence found in nuclear proteins

Question 22

how was NLS discovered

Answer 22

researchers investigating how T-antigen proteins entered the nucleus

Question 23

NLS discovery experiment #1

Answer 23

researchers infected group 1 rats with SV40 virus. Group 2 rats with mutated SV40 virus
SV40 T-antigens could get inside the nucleus\
Mutated SV40 T-antigens were stuck in cytosol
Mutated SV40 virus had one incorrect amino acid (codon 128)

Question 24

NLS discovery experiment #2

Answer 24

researchers made partial T-antigen proteins
proteins without AA 126-132 could not enter nucleus
therefore, 126-132 were necessary for nuclear localization

Question 25

NLS discovery experiment #3

Answer 25

AAs 126-147 were attached to a B-GAL protein and made it into the nucleus
therefore, AAs 126-147 are sufficient for nuclear localization

Question 26

importin proteins

Answer 26

associate with NLS and nuclear pores

Question 27

what is required for nuclear export

Answer 27

nuclear export signal (NES)

Question 28

NES

Answer 28

amino acid sequence found in proteins that leave the nucleus, or help RNAs leave the nucleus

Question 29

exportin protein

Answer 29

associate with NES or tRNA and nuclear pores

Question 30

what drives transport in the correct direction

Answer 30

protein called Ran

Question 31

2 versions of Ran

Answer 31

1. Ran-GTP active found in nucleus

2. Ran-GDP inactive found in cytosol

Question 32

what does Ran-GTP have a high affinity for

Answer 32

importins and exportins

Question 33

what occurs when Ran-GDP enters the nucleus

Answer 33

Guanine exchange factor protein replaces GDP with GTP

Question 34

what occurs when Ran-GTP enters the cytosol

Answer 34

GTP is hydrolysed to GDP with the GTPase activating proteins

Question 35

when Ran-GTP binds to importin in the nucleus, importin does what?

Answer 35

releases its cargo

Question 36

when Ran-GTP binds to exportin in the nucleus, exportin does what?

Answer 36

binds to its cargo