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Molecular Biology Test 1 > Notes 7 > Flashcards

Notes 7 Flashcards

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1
Q

Euchromatin

A

Easily makes complexes for transcription
Lighter staining
thought to have structural genes

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2
Q

Heterochromatin

A

Transcriptionally inactive
Densely stained
condensed

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3
Q

What holds the ribosomal RNA genes?

A

Nucleolus

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4
Q

3 components of ribosome

A

28 S rRNA
18 S rRNA
5.8 S rRNA

45 S

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5
Q

3 steps to view ribosomal genes

A
  1. Isolate oocyte nuclei
  2. Centrifuge in sucrose gradient
  3. View with the electron microscope to locate ribosomal genes
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6
Q

What’s used to view rDNA

A

electron microscope

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7
Q

Satellites

A

Chromosome segments seaparated from the main body by a constriction (satellite stalk). Often consist of heterochromatin; similar to the knobs of plants.

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8
Q

Nucleolar Organizer Regions (NOR)

A

Sites of rRNA genes.
Appear as secondary constricions in mitotic chromosomes.
Seen as nucleoli during interphase.

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9
Q

What are found at NORs

A

clustered repeats of the ribosomal subunits

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10
Q

How many NORs do humans have?

A

2!! We’re diploid.

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11
Q

C-Banding

A

Chromosomes are fixed in 0.2N HCl then .07N NaOH, overnight in 2x SSC, and stained with giemsa

Stains centromeric heterochromatin
Quick way of distinguishing acro from metacentric chromosomes

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12
Q

Giemsa

A

Most common stain
planar (can intercholate)
Salt so it uniformaly is attracted to DNA

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13
Q

Giemsa components

A

Methylene Blue

Thiazine moiety

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14
Q

Thiazine moiety

A

interacts with phosphate groups of DNA and can side stack along the molecule

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15
Q

R-banding

A

R stands for reverse
Giemsa stained chromosomes using PHASE CONTRAST MICROSCOPY
G-C rich DNA are the interbands!!!

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16
Q

Q banding

A

Quinacrine Stain

Chromosomes are stained with quinacrine hydrochloride

Stain fluoresces strongly in UV light
AT rich regions react strongly and enhance fluorescence
GC rich regions quench fluorescense

17
Q

G-Banding

A

Chromosomes are fixed in methanol-acetic acid (carnoys reagent) and stained with Giemsa

Provides chromosomal landmarks by demonstrating several bands along the length of the chromosome

18
Q

What bands (+ or -) are dark?

A

Positive

19
Q

Chromosome landmark

A

A consistent morphological feature of the banded chromsome (telomere, centromere, precise staining band)

20
Q

Region

A

Area lying between 2 landmarks

21
Q

4 things required for band designation

A
  1. chromosome number
  2. arm symbol
  3. region number (# between landmarks)
  4. Band number

Molecular Biology Test 1 (4 decks)

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