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Cell Biology > Lecture 5 Reading > Flashcards

Lecture 5 Reading Flashcards

0
Q

Mitotic chromosomes

A

Highly condensed chromosomes in a dividing cell

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1
Q

Karyotype

A

The display of 46 human chromosomes at mitosis

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2
Q

What three types of specialized nucleotide sequences in DNA contorl replication, separation and partition into daughter cells

A

DNA replication origin
Centromere
Telomere

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3
Q

Replication origin

A

Nucleotide sequence

The location at which duplication of DNA begins

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4
Q

Centromere

A

Nucleotide sequence

Allows one copy of each duplicated and condensed chromosome to be pulled into a daughter cell when a cell divides

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5
Q

Kinetochore

A

Protein complex forms at centromere and attaches duplicated chromosomes to the mitotic spindle so they can be pulled apart

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6
Q

Telomere

A

The ends of a chromosome
Contain repeated nucleotide sequences that enable ends of chromosomes to be efficiently replicates
Form structures that protect the end of the chromosome from being mistaken by the cell for a broken DNA molecule that needs repair

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7
Q

Proteins that bind to dna to form eukaryotic chromosomes 2

A

Histones

Non histone chromosomal proteins

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8
Q

Chromatin

A

Complex of histone and non histone chromosomal protein with nuclear dna if eukaryotic cells

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9
Q

Nucleosome

A

Most basic level of chromosome packing

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10
Q

Linker DNA

A

Exposed dna between nucleosome core particles

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11
Q

Histone octamer

A

Forms a protein core around which the double stranded DNA is wound

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12
Q

Nucleosomes repeat at intervals of

A

About 200 nucleotide pairs

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13
Q

Epigeneric inheritance

A

A form of inheritance that is superimposed on the genetic inheritance based on DNA

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14
Q

Two types of chromatin

A

Heterochromatin - highly condensed

Euchromatin - not as condensed

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15
Q

Position effect

A

Chromosome breakage and rejoining that translocate normally euchromatic DNA into the neighborhood of heterochromatin

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16
Q

Position effect variegation

A

Once a heterochromatin condition is established on a piece of chromatin, it tends to be stably inherited by all of the cell’s progeny

17
Q

How is DNA packaged

A

DNA tightly wrapped in a left handed coil of 1.7 turns. All four of the histones that make up core of nucleosome are small proteins. They share a structural motif known as the histone fold, which is formed from three alpha helices connected by two loops.

18
Q

How large is interface between DNA and histones

A

142 h bonds formed between DNA and histone core in each nucleosome, half of these bonds form bet. The amino acid backbone of the histones and the sugar phosphate backbone of dna. Hydrophobic interactions and salt linkages also hold dna and protein together in nucleosome. More than one fifth of a, acids in histones is lysine or arginine, positive charges neutralize dna backbone which is negative.

19
Q

Chromatin remodeling complexes

A

Include a subunit that Hydrolyzes ATP. Subunit binds to protein core of nucleosome and to double stranded dna that winds around it. ATP hydrolysis releases energy to move Dna and changes structure of nucleosome.

20
Q

Linker stone

A

Histone H1 larger than individual core histones. Single h1 binds to each nucleosome contacting dna and protein, and changing path of dna as it exits from the nucleosome.

21
Q

How are core histones covalently modified

A

Acetylation of lysines, mono, di and trimethylation of lysines, and phosphorylation of serines. Occur on unstructured n-terminal histone tails that protrude from nucleosome. Are reversible.

22
Q

Histone acetyl transferase

A

Adds acetyl groups to lysines

23
Q

Histone deacetylate complexes

A

Remove acetyl groups from lysines

24
Q

Histone methyl Transferases and histone demethylases

A

Add and remove methyl groups

25
Q

What does acetylation of lysine cause

A

Loosens chromatin structure, removes lysine’s positive charge and affinity of tails for adjacent Nucleosomes,

26
Q

Most profound effect of histone modification

A

Their ability to recruit specific other proteins to the modified stretch of chromatin. Recruited proteins act with modified histones to determine how and when genes will be expressed, as well as other chromosomal functions.

27
Q

Histone variants

A

Histones extra of standard core histones

28
Q

When are major histones made? Variants?

A

S phase. Interphase.

29
Q

Histone code

A

Combination known to have specific meaning for the cell in the sense that they determine how and when DNA in Nucleosomes is to be accessed

30
Q

Reader complex

A

Protein domains linked together as modules in a single large protein or protein complex, which thereby recognizes a specific combo of histone modifications

31
Q

Lampbrush chromosomes

A

Stiff and enormously extended chromosomes in growing amphibians. Paired in preparation for meiosis, clearly visible in light microscope.

32
Q

Polytene cells of flies

A

Fruit fly drosophila

Multiple cycles of dna synthesis make cell unusually large. Polyploid cells.

33
Q

Polytene chromosomes

A

Copies of each chromosome are aligned side by side to create thse giant chromosomes

34
Q

What happens to a gene when it is highly expresses

A

It’s position in interior of nucleus changes

35
Q

Nucleolus

A

Ribosome unit formation site

36
Q

Canal bodies and inter chromatin granule clusters

A

Organelles inside nucleus of plant and animal cells

37
Q

Nuclear matrix or scaffold

A

Insoluble material left in nucleus after a series of biochemical extraction steps

38
Q

Purposes of compaction during mitosis

A

When condensation complete, sister chromatids have been disentangled
Compaction of chromosomes protects the relatively fragile dna molecules from being broken as they are pulled apart

39
Q

When does condensation of interphase chromosomes into mitotic chromosomes begin

A

In early M phase. Connected with progression of cell cycle. Gene expression shuts during M phase.

40
Q

Cohesive and condensins

A

Aid compaction of chromosomes

Cell Biology (35 decks)

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