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Human Molecular Biology > Structure of Eukaryotic Chromosomes > Flashcards

Structure of Eukaryotic Chromosomes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

approx how much dna is in a single human cell

A

1.8m

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2
Q

how much compaction if needed to fit the dna into the nucleus

A

approx 180,000 times

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3
Q

why is dna compacted

A

to prevent it from damage and to regulate DNA metabolism

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4
Q

DNA in non dividing cells forms

A

chromatin

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5
Q

DNA during mitosis forms

A

chromosomes

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6
Q

the repeating unit of chromatin is the

A

nucleosome

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7
Q

each nucleosome comprises two molecules of each of the

A

four core histones

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8
Q

each core histone dimer has how many DNA binding surfaces

A

6

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9
Q

each core histone dimer has 6 DNA binding surfaces that organises how many DNA turns

A

3

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10
Q

the histone octamer organises how many base pairs of DNA in how many turns

A

145 base pairs of DNA in 1 and 3/4 helical turn of DNA

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11
Q

Individual nucleosomes can be prepared by limited digestion of chromatin with

A

micrococcal nuclease

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12
Q

once chromatin has been digested with micococcal nuclease how is it separated

A

on sucrose gradients

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13
Q

histones are readily solubilised from chromatin by

A

dilute acids, e.g. 1M (10%) HCl

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14
Q

Which amino acids are histones rich in

A

positively charged arginine and lysine

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15
Q

how many species of histones exist

A

five species, designated h1 to h4. H5 is a type of h1

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16
Q

which histones form various aggregates

A

H2a, H2b, H3 and H4

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17
Q

histone h1 (H5) is not present in the

A

nucleosome

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18
Q

nucleosomes are ____ conserved

A

highly

19
Q

nucleosomes are ____ proteins

A

basic due to lysine and arginine

20
Q

histones h3 and h4 preferentially aggregate to form

A

tetramers

21
Q

tetramers contain how many molecules of each histone

A

two

22
Q

histone h2a and h2b also aggregate but in

A

stages

23
Q

how many types of interaction do histones make with dna

A

five

24
Q

what are the two types of chromatin

A

heterochromatin and euchromatin

25
Q

heterochromatin can be described as

A

highly condensed, inactive genes

26
Q

euchromatin can be described as

A

extended structure, active genes

27
Q

what is the first level of organisation

A

the 11nm fibril

28
Q

the 11nm fibril has the appearance of a necklace and each bead is known as a

A

nucleosome

29
Q

the short length of DNA joining any two nucleosomes is termed

A

linker dna

30
Q

how many base pairs of DNA makes up linker DNA

A

50bp

31
Q

the first level of organisation of DNA is how many nm thick?

A

11nm, it is called the 11nm fibril

32
Q

what is the second level of structural organisation

A

the 30nm solenoid fibre

33
Q

how many nucleosomes per turn are in the solenoid helix

A

six

34
Q

which histone is required for the condensation to solenoid 30nm fibre

A

histone h1

35
Q

the 30nm fibre is inactive in

A

rna synthesis (transcription)

36
Q

what is the third level of structural organisation

A

loops, rosettes and coils

37
Q

what is the fourth level of structural organisation

A

chromatids

38
Q

chromatin is maximally condensed in

A

mitosis

39
Q

how many micrometers long are chromatids

A

5 micrometers

40
Q

what is the nuclear scaffold

A

a network of proteins that cross tie DNA loops

41
Q

topoisomerase 2 and protein SC2 are major components in the

A

nuclear scaffold

42
Q

topoisomerase 2 and protein SC2 bind to which region in the chromosomal DNA

A

SAR - Scaffold attachment regions

43
Q

SARs are highly rich in which bases

A

AT rich

44
Q

what do SARs participate in overall

A

chromosome assembly and maintenance

Human Molecular Biology (4 decks)

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