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Chapter 12: DNA Organization in Chromosomes Flashcards

1
Q

This is the decondensed nucleoprotein structure eukaryotic chromosomes are in during interphase.

A

chromatin

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2
Q

Why do eukaryotes organize their DNA into chromatin?

A

The genome is huge, and this is an efficient way of packing it.

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3
Q

Chromatin’s structure resembles ______.

A

beads on a string

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4
Q

The “beads” in chromatin are called _____.

A

nucleosomes

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5
Q

Nucleosomes are made of _____.

A

histone proteins

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6
Q

Histone proteins are _____ charged.

A

positively

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7
Q

How many histone molecules are there per histone?

A

Eight.

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8
Q

True or false: histone proteins are highly conserved.

A

True.

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9
Q

Why does DNA stick to the histone particles?

A

They are positively charged, and DNA is negatively charged due to the phosphates, so they form tight ionic bonds.

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10
Q

How many types of histones are there?

A

Four.

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11
Q

What are the four types of histones?

A

H2A, H2B, H3, and H4

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12
Q

H2A and H2B histones are ______ rich.

A

slightly lysine

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13
Q

H3 histones are _____ rich.

A

arginine

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14
Q

H4 histones are _____ rich.

A

arginine

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15
Q

This type of histone is not part of the core particle, but is made of linker DNA and wraps around the core.

A

H1 protein

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16
Q

The nucleosome core particle is comprised of _____ base pairs.

A

147

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17
Q

This particle is made up of two tetramers and is a form of linker DNA.

A

Nucleosome core particle

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18
Q

What must the packing ratio be in order for DNA to fit in the nucleus?

A

500 to 1.

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19
Q

How many levels/orders of condensation are there in chromatin condensation?

A

Four.

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20
Q

In this level of condensation, chromatin is reduced to 1/3 of original length.

A

Level 1

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21
Q

What happens in level 1 of chromatin condensation?

A

The 147 base pairs wrap around the histone.

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22
Q

The histone with the 147 base pairs wrapped around it is called a _____.

A

Nucleosome

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23
Q

In this level of condensation, chromatin is reduced by an additional 6-fold, resulting in the chromatin being 18-fold smaller than its initial size.

A

Level 2

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24
Q

The structure formed by nucleosomes coiling and stacking in level 2 of chromatin condensation is called the _____.

A

solenoid

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25
This protein is necessary for compaction into the solenoid.
H1 linkers
26
What shape is the solenoid?
Tubular, like a cylinder.
27
At this level of condensation, chromatin is at 180-fold compaction.
Level 3
28
At this level of compaction, the solenoids are folded into looped domains to make a chromatin fiber.
Level 3
29
What are chromatin fibers made of?
Looped domains of solenoids.
30
At this level of compaction, the chromatin fibers are packed into the metaphase chromosomes at the 500-fold level.
Level 4
31
When does the DNA compact into level four chromosomes?
Only when preparing for mitosis or meiosis.
32
Changes in gene expression or phenotype not attributable to changes in the DNA sequence is called _____.
epigenetics
33
These have no secondary structure and protrude through the minor groove channels, actually touching the DNA.
Histone tails
34
What is the purpose of histone tails?
They provide targets for chemical modifications such as acetylation and methylation, which in turn loosens DNA's bond with the histone and allows proteins to come in and work on the DNA.
35
How do proteins and enzymes get in the tightly packed DNA for protein remodeling and changes in gene expression?
Histone tails act as targets for methyl or acetyl groups. These remove the positive charge from the histones, loosening the ionic bond between them and the negatively charged DNA.
36
This neutralizes positive histone charges so that the DNA is only loosely associated with them.
Acetylation
37
This histone modification is characteristic of gene expression.
Acetylation
38
This recruits repressor proteins by acting like a little flag telling the proteins to come stick to the histones.
Methylation
39
This histone modification is characteristic of gene repression.
Methylation
40
This form of chromatin is uncoiled and active.
euchromatin
41
This form of chromatin is condensed and inactive.
heterochromatin
42
What are the two types of heterochromatin?
facultative and constitutive
43
This type of heterochromatin can switch to euchromatin when it becomes less tightly bound.
Facultative
44
This type of heterochromatin never becomes active/expressed and has tandem repeats.
Constitutive
45
What is the function of constitutive heterochromatin?
Structural and functional support
46
What are the two different types of human repetitive sequences?
Tandem repeats and interspersed repeats
47
This type of repetitive sequence is when the same sequence is repeated over and over again.
tandem repeats
48
This type of repetitive sequence is when the same sequence pops up here and there.
interspersed repeats
49
True or false: Over half of the DNA in the human body never gets expressed.
True
50
True or false: methylation is always good in DNA.
False
51
The position of a gene or group of genes relative to all other genetic material being affect their expression is called a _____.
position affect
52
Staining patterns where only the centromeric region takes up stain is called _____.
C-banding
53
Staining patterns where different regions along the length of the chromosome take up stain is called _____.
G-banding
54
This region of the centromere supports the function of chromosomal segregation.
CEN region
55
Telomeric DNA sequences protect the stability and integrity of the chromosome because of _____.
tandem repeats
56
This component of the telomere contributes to its heterochromatic nature by facilitating methylation of the histone H3K9.
TERRA
57
This type of repetitive DNA can potentially move to different parts of the genome.
Transposable sequences
58
These are short transposable sequences.
Short interspersed elements (SINEs)
59
These are longer transposable sequences.
Long interspersed elements (LINEs)
60
Genes that may resemble the original gene but are not transcribed due to significant mutational alteration are called _____.
pseudogenes

Genetics (6 decks)

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