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Cell Biology > Quiz 3 > Flashcards

Quiz 3 Flashcards

1
Q

Genome

A

entirety of information contained within an organism’s gene

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2
Q

Base pairing rules

A

Adenine (purine) pairs with thymine (pyrimidine) with two hydrogen bonds

Guanine (purine) pairs with cytosine (pyrimidine) with three hydrogen bonds

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3
Q

Gene

A

Basic unit of heredity

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4
Q

Introns

A

non-coding regions of a gene

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5
Q

Exons

A

Coding regions of a gene

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6
Q

During RNA processing, ______ are removed, and ______ form mature RNA.

A

Introns, exons

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7
Q

Describe regulatory sequences

A

Do not encode for a protein
Help regulate gene expression

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8
Q

What are four examples of regulatory sequences?

A

Promotors, terminators, enhances, silencers

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9
Q

Describe a promotor.

A

Located upstream
Where RNA polymerase binds and initiates transcription

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10
Q

Describe a terminator.

A

Located at 3’ end
Acts as a stop signal for RNA polymerase

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11
Q

Describe enhancers: where are they located, what binds to them, and what is their function?

A

Located upstream or downstream

Bound by activators

Up regulate gene transcription

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12
Q

Describe silencers: what binds to them and what is their function?

A

Bound by repressors

Down regulate gene transcription

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13
Q

What does the solenoid model propose?

A

Nucleosomes are arranged in a left helical confirmation with 6 or more nucleosomes per turn. This shortens DNA length by 50-fold.

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14
Q

Chromatin exists in two forms:

A
  1. Euchromatin
  2. Heterochromatin
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15
Q

Describe euchromatin during interphase.

A

dispersed in nucleus and replicated throughout S phase

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16
Q

What are characteristics of euchromatin?

A
  1. Gene-rich
  2. Less compact
  3. Actively transcribed region of chromatin
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17
Q

The histone tail amino acids of euchromatin are __________.

A

Acetylated

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18
Q

Why are the histone tail amino acids in euchromatin acetylated?

A

Acetylation increases negative charge on histone proteins
—> Reduces histone-DNA affinity
—> Reduces chromatin compaction
—> Allows easier access to DNA

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19
Q

Nucleosome contains a protein core made up of four histone core proteins:

A
  1. H2A
  2. H2B
  3. H3
  4. H4
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20
Q

All histone core proteins have variants with the exception of which histone core protein?

A

H4

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21
Q

List the variants of each histone core protein.

A
  1. H2A — H2AX, H2AZ
  2. H2B — TH2B, TSH2B
  3. H3 — H3.1, H3.2
  4. H4 — no variants
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22
Q

Describe amino-terminal tails.

A

Unstructured and highly mobile

Comprised of about 30 amino acids

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23
Q

Amino-terminal tails are subjected to several forms of covalent modifications:

A

Acetylation of lysines
Phosphorylation of serines
Mono, di, or trimethylation of lysines

24
Q

Chromatin

A

DNA-histone complex contained in nucleus

25
Chromatin condenses to form ___________.
Chromosomes
26
Centromere
DNA sequence that links sister chromatids
27
What are the four major configurations of chromosomes?
1. Metacentric - centromere is centered * Results in similar arm lengths 2. Submetacentric - centromere is off-center * Results in different arm lengths 3. Telocentric - centromere is at end of chromosome * Results in long, single arms 4. Acrocentric - centromere located near end of chromosome * Stalk and bulb appearance * E.g., human Y chromosome
28
Describe telomeres: what they are, where they are located, and what is their function?
- consist of noncoding repetitive nucleotide sequences - Located at chromosome tips - Protect and stabilize ends of chromosomes
29
Origins of replication
sequences of nucleotides that determine where DNA replication begins
30
How many origins of replication are in human chromosomes?
~ 30,000
31
Why do purines always base pair with pyrimidines?
* Purines: double ring structure * Pyrimidines: single ring structure * Two pyrimidines: distance too large to form hydrogen bonds
32
Hydrogen bonds between base pairs form when _________ atom is ~2 Å away from an __________ atom (e.g., _____ and ____)
Hydrogen; electronegative; N; O
33
Nucleosome
basic structural and functional unit of chromatin
34
Association of DNA into nucleosomes shortens DNA length _______.
7-fold
35
H1
non-core histone protein
36
30-nm fiber
Contains any chromatin region not being actively transcribed/replicated
37
Bead-on-a-string form
Contains chromatin regions actively being accessed
38
Under a microscope, euchromatin is seen as…
Lightly stained regions
39
Why is euchromatin seen as lightly stained regions under a microscope?
Euchromatin retains fewer stained particles
40
List the Writers.
* Methyltransferases * Acetylases * Kinases
41
List the Erasers.
* Demethylases * Deacetylases * Phosphatases
42
What did the Watson-Crick model (1953) propose?
DNA is made up of two strands of nucleotides that twist around each other to form a right-handed helix
43
DNA strands are _______.
Antiparallel
44
What does it mean for DNA strands to be antiparallel?
3’ end of one strand faces 5’ end of other strand (3’-5’ and 5’-3’)
45
What does the Watson-Crick model say about base pairing?
Bade pairing takes place between a purine and a pyrimidine
46
Introns and exons are transcribed into ________.
pre-mRNA
47
_____ mRNA is translated into a protein.
Mature
48
What is the function of H1 and what is the result of this function?
Changes DNA path as it exist nucleosome -> further compacts chromatin
49
What are 30-nm fibers?
Short, thick fiber of nucleosomes stacked on top of each other that are 30 nm in diameter
50
30-nm fibers are best explained by which model?
Solenoid model
51
Erasers
Enzymes that catalyze removal of chemical groups from amino-terminal tails
52
Writers
Enzymes that catalyze addition of chemical groups from amino-terminal tails
53
What is the histone code?
Histone modifications encode signals for cells
54
Give examples of signals encoded by modifications in the histone code.
1. DNA damage and need for repair 2. Gene expression 3. Gene silencing 4. Chromatin modification
55
Readers
Regulatory proteins that decode histone codes
56
How do readers work?

Cell Biology (24 decks)

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