Chapter 11

DNA interaction

________ with histones and non- histone proteins produces sufficient level of compaction to fit into a cell nucleus.

Condensins

________ may further condense chromosomes into a compact bundle for mitosis.

Metaphase chromosomes

________ stained with Giemsa stain have alternating bands of light and dark staining.

Nucleosome

________: confirmed by crystal structure; condenses naked DNA 7- fold to a 100 A fiber.

Compaction

________ allows DNA to fit in cell nucleus.

Fluorescent

________ in situ hybridization (FISH) is used to characterize genomes.

Promoters

________ are exposed by removing or repositioning nucleosomes.

Chromosomes

________: separate pieces of chromatin that behave as a unit during cell division.

Transcription

________ requires changes in chromatin structure.

Constitutive

________: condensed in all cells.

Accessibility

________ for proteins that initiate transcription, replication, and further compaction.

Dosage compensation

________ in mammals so that X- linked genes in XX and XY individuals are expressed at same level.

X chromosome

________ inactivation in female mammals occurs through heterochromatin formation.

SKY

In ________, probes specific for each chromosome are labeled with a different fluorescent dye.

Nucleosome core

________ is an octamer of 2 of each of histones H2A, H2B, H3, and H4.

Histone H1

________ associates with linker DNA as it enters and leaves the nucleosome core.

Heterochromatin

________: highly condensed, usually inactive transcriptionally.

Enzymes

________ can add chemical groups.

DNA

________ bends sharply at several places as it wraps around the core histone octamer.

Redial loop scaffold

________: hypothetical model (preliminary experimental support); through progressive compaction of 300 A fiber, condenses DNA to rodlike mitotic chromosomes that are 10, 000 times more compact than naked DNA.

Base sequence

________ dictates preferred nucleosome positions along the DNA.

identical DNA

All cells have ________.

FISH

________ depends on hybridization between metaphase chromosomes and a labeled DNA sequence.

H2B

Core histones 2x (H2A, ________, H3, and H4) make up the nucleosome.

genetic function

Spacing and structure of nucleosomes affect ________.

Spectral karyotyping

________ (SKY) is a variation of FISH.

hypothetical model

Supercoiling: ________ (300 A fiber predicted has been seen); causes additional 6- fold compaction, achieving a 40- to 50- fold condensation relative to naked DNA.

Euchromatin

________: relaxed, usually active transcriptionally.

nucleosomal chromatin

100 A(n) ________ is compacted into 300 A fiber by supercoiling.

tails

Modified ________ can alter nucleosomes and bind chromatin modifier proteins.

Promoters of inactive genes

________ are hidden in nucleosomes.

Acetylation

________: histone acetyltransferase adds acetyl group to histone tails.

band

Each ________ contains many DNA loops and ranges from 1 to 10 Mb in length.

Chromatin

________: generic term for any complex of DNA and protein found in a nucleus of a cell; 1 /3 DNA, 1 /3 histones, 1 /3 non- histone proteins.

Methylation

________: histone methyltransferase adds methyl group to histone tails.

Histones

________: small, positively charged, highly conserved; bind to and neutralize negatively charged DNA.

Nucleosome

________ is the fundamental unit of chromosomal packaging.

Acetylation

________ prevents close packing of nucleosomes.

Methylation

________ affect depends on specific amino acid modified.

chromatin

generic term for any complex of DNA and protein found in a nucleus of a cell; 1/3 DNA, 1/3 histones, 1/3 non-histone proteins

chromosomes

separate pieces of chromatin that behave as a unit during cell division

Nucleosome

confirmed by crystal structure; condenses naked DNA 7-fold to a 100 A fiber

Redial loop-scaffold

hypothetical model (preliminary experimental support); through progressive compaction of 300 A fiber, condenses DNA to rodlike mitotic chromosomes that are 10,000 times more compact than naked DNA

histones

small, positively charged, highly conserved; bind to and neutralize negatively charged DNA

5 types of histones

H1, H2A, H2B, H3, and H4

functions of non-histone proteins

structural role (chromosome scaffold), chromosome replication, chromosome segregation, active in transcription

short arm

p arm

long arm

q arm

heterochromatin

highly condensed, usually inactive transcriptionally

constitutive

condensed in all cells

facultative

condensed in only some cells and relaxed in other cells

Euchromatin

relaxed, usually active transcriptionally

methylation

histone methyltransferase adds methyl group to histone tails

Acetylation

histone acetyltransferase adds acetyl group to histone tails