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Flashcards in Eukaryotic Gene Expression Deck (40)
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1

Histones

-proteins that wrap around DNA
-about 100 AAs per histone
-positive AAs bind tightly around histones to the negatively charged DNA
-highly conserved protein across species

2

What are the 4 common types of histones?

-H2A
-H2B
-H3
-H4

3

Nucleosomes

-10nm fiber
-"beads on a string"
-DNA that is wound 2x around an octamer of histones (2 histones of each type)

4

Histone tails protrude outwards from a ____

nucleosome

5

Histone Tails

-consist of amino acids that are available for chemical modification
-the N terminus of an AA

6

Histones only briefly leave DNA during ___

replication

7

30nm Fiber

-consists of interactions between histone tails and linker DNA (DNA "strings" between nucleosomes)
-H1 involved here
-takes the 10nm fiber and folds it into a chromatin fiber
-seen in interphase of cell cycle when the chromosomes are decondensed

8

300nm Fiber

-looped domains
-formed when the 30nm fibers form loops that attach to a chromosome scaffold made of proteins

9

Chromosome scaffold is rich in ___ and ___

topoisomerase and H1

10

Metaphase/Mitotic Chromosome

-most tightly folded
-occurs during metaphase when the looped domains fold to form sister chromatids

11

Centromere

-middle of the mitotic chromosome that binds to the mitotic spindle
-present during metaphase

12

Chromatin

-complex of DNA and protein
-changes depending on the stage of the cell cycle

13

In interphase, there are regions of DNA that are more ___ than others

condensed

14

Heterochromatin

-tightly packed
-contains less frequently transcribed genes

15

Euchromatin

-loosely packed
-contains "housekeeping genes" -- genes that need to be transcribed all the time
-genes are more accessible

16

Supercoiling

helps keep DNA wound tightly

17

Single Copy DNA

one gene with no duplications

18

Repetitive DNA

-gene families
-lots of copies of the same gene -- these duplicates have evolved throughout time
-lots of these are found on the X chromosome
-ex. smell receptors

19

With age, our ___ get shorter

telomeres

20

Cancer has a way of replacing ___ so that they can have uncontrolled cell growth

telomeres

21

Acetylation of histone tails leads to ___ of DNA folding

loosening
(tail goes from positively charged to neutral)

22

Lots of acetylation means ___ transcription

increased

23

Deacetylation of histone tails leads to ___ of DNA folding

tightening

24

In general (depends on the AAs present), methylation of histone tails leads to ___ of DNA folding

loosening

25

Phosphorylation of histone tails (addition of negative charges) leads to ___ of DNA folding

loosening
(negative charge of DNA and PO4 repel each other)

26

How can you regulate the step between DNA and pre-mRNA

-regulating transcription initiation

27

How can you regulate at the level of RNA processing (pre mRNA to mature mRNA)?

-alternative splicing (produce different isoforms by varying the exons that we put together during RNA processing)

28

Where does translation of mRNA occur?

cytosol

29

What happens to mRNA if it is not translated?

it is degraded in the cytosol

30

What processing occurs between polypeptide and active protein formation in the cytosol?

protein processing (can be either by chemical modification or cleavage)