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Bio97 > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

chromosome number and size

A

are species specific, but are not associated with the complexity of an organism

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2
Q

How many chromosomes do cats have?

A

38

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3
Q

How many chromosomes do carp have?

A

104

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4
Q

How many chromosomes do humans have?

A

46

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5
Q

What is a Karyotype?

A

An organized image of the chromosomes in a nucleus

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6
Q

What do chromosomes look like during interphase?

A

highly DEcondensed and difficult to visualize

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7
Q

In what phases can chromosomes be individually visualized and identified?

A

about mid-prophase to metaphase

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8
Q

Are centromeres always in the CENTER of a chromosome?

A

No, they are almost always of UNEQUAL lengths

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9
Q

What is a centromere?

A

What binds two chromatids together to form a chromosome. They determine chromosome shape.

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10
Q

What is chromatin?

A

nucleic acids (DNA) and proteins that make up chromosomes

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11
Q

What is euchromatin?

A

LOOSELY CONDENSED chromosome regions that are more ACTIVELY TRANSCRIBED

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12
Q

What is heterochromatin?

A

TIGHTLY CONDENSED chromosome regions with FEWER expressed genes

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13
Q

Why do euk. chrom. need to be compacted?

A

-essential for cell division
-regulating gene expression (position effect variegation- PEV, euch/hetero chromatin)
-saves space

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14
Q

In “beads on a string” what are the beads, and what is the string?

A

“beads”= nucleosome
“string”= linker DNA

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15
Q

What are the 5 components of a nucleosome core particle ?

A

1) 2 H2A
2) 2 H2B
3) 2 H3
4) 2 H4
5) 146s bps of “core” DNA
-(linker) DNA

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16
Q

What is PEV?

A

Position effect variegation: gene expression is controlled by the state of chromatin (euch/hetero) in which a gene is located, so if a gene is moved to a diff. region (euch/hetero) will change how it is expressed

17
Q

What is facultative heterochromatin?

A

Can switch between euch/hetero-chromatin to activate genes at certain times (eg. development) on in certain tissues

18
Q

What is constitutive heterochromatin?

A

Regions of the genome that are always heterochromatic and transcriptionally inert

19
Q

What kind of chromatin does a centromere lie in?

A

Heterochromatic chromatin/ heterochromatin

20
Q

At what point during the cell cycle are centromeres most important?

A

During metaphase, when the spindles attach to them

21
Q

Define open promoters.

A

initiate transcription of genes for constitutively active genes
eg. basic cellular functions

22
Q

Define closed/covered promoters.

A

-regulate transcription of genes by requiring chromatin remodeling (displacement or removal of nucleosomes) to enable RNA polymerase to bind
-generally contain TATA boxes
-competition of nucleosomes and transcript. factors for binding

23
Q

Define open chromatin.

A

-relaxed nucleosomes
-allows access by regulatory proteins
-DNase 1 sensitive–> transcribable

24
Q

Define closed chromatin.

A

-DNA covered by nucleosomes
-restrict access of regulatory to proteins–> transcriptionally silent

25
Q

Where are DNase 1 hypersensitivity regions?

A

-at open regions

26
Q

What does DNase 1 do?

A

-enzyme randomly cuts DNA in open regions
-used to test if a region is open (hypersensitive) or closed

27
Q

What are “writers?”

A

Enzymes that ADD chemical groups that modify histones

28
Q

What are “erasers?”

A

Enzymes that REMOVE chemical groups to modify histones

29
Q

What are “readers?”

A

Proteins that recognized modified histones; active or deactivate the site

30
Q

What are HATs?

A

-histone acetyltransferases
-writers
-ADD acetyl groups
–> euchromatin (increase transcription)

31
Q

What are HDACs?

A

-histone deacetylases
-erasers
-REMOVE acetyl groups
–> heterochromatin (decrease transcription)

32
Q

What are the two primary mods added to histones?

A

1) addition or removal of acetyl groups

2) addition or removal of methyl groups

33
Q

What are HMTs?

A

-histone methyltransferases
-writers
-ADD methyl groups

34
Q

What are HDMTs?

A

-histone demethylases
-erasers

35
Q

Define epigenetic.

A

Heritable patterns or changes in gene expression that are not associated with any change in DNA sequence.

36
Q

What is Nucleotide Methylation?

A

-epigenetic
-adds methyl group to usually to cytosine (C) in DNA and usually turns expression off

37
Q

What does Histone 1 (H1) do?

A

Stabilizes the nucleosome core particles

38
Q

Rank the condensation of DNA.

A

naked DNA–>histones–> nucleosomes–> solenoid–> loop domains–> chromatid–> metaphase chromosomes

Bio97 (12 decks)

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