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Bio 130 > Chapter 18 > Flashcards

Chapter 18 Flashcards

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Biology 101 flashcards
1
Q

What is the structure of the purines

A

double-ring

A and G

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2
Q

What is the structure of the pyrimidines

A

Single ring

T and C

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3
Q

What did Chargaff discover

A

DNA from different cells have the same percentage of each of the four bases

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4
Q

Percentages of bases do not vary with…

A

tissues age, within an individual, nutritional state, and environment

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5
Q

Where does the DNA vary

A

Species to species

closely related species have similar compositions

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6
Q

What was Chargaff’s most important discovery about DNA base amounts

A

A=T
G=C
A+G=C+T

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7
Q

What is Watson and Crick’s DNA model

A

Double-helix

polymer with a backbone of repeating sugars and phosphate groups

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8
Q

what is the diameter of the helix

A

2nm

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9
Q

What holds together the purine-pyrimidine pairs

A

Hydrogen bonds

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10
Q

What is significant about the Hydrogen bonds versus the covalent bonds holding the backbone together

A

The hydrogen bonds can easily be broken for things like replication while leaving the nucleotides intact

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11
Q

How many nucleotides per turn

A

10

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12
Q

DNA denaturation

A

The DNA splitting apart which can be induced experimentally with heat

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13
Q

DNA renaturation

A

the reverse of denaturation where you lower the temp and the DNA comes back together

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14
Q

What determines the melting temperature of DNA

A

Base composition (GC bases increase temp) and proper pairing (increases temp)

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15
Q

Why do GC base pairs take longer to melt

A

because they are held together by 3 H bonds rather than the 2 H bonds that hold AT together

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16
Q

Genome

A

the DNA that contains one complete copy of genetic information

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17
Q

What is B-DNA

A

Right hand helix

main form of DNA

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18
Q

What is Z-DNA

A

left hand helix

zig-zag pattern of backbone

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19
Q

What is the function of Z-DNA

A

process by which some genes are expressed

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20
Q

What is the major groove generally the site for

A

direct info readout

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21
Q

What is the minor groove important for

A

target for a few regulatory and structural proteins

22
Q

What is the nucleoid

A

region where the bacterial chromosome resides

23
Q

what is the deal with the bacterial nucleoid

A

they have super long DNA that is somehow packaged into a tiny space and scientists still aren’t sure how they do it

24
Q

Histones

A

group of proteins with strong positive charge

25
Q

What charge does DNA have

A

negative

26
Q

what is chromatin

A

DNA packaged together with proteins

27
Q

Nucleosome

A

proteins are clustered at 2 bp intervals along the DNA molecule in chromatin fibers
(beads on a string)

28
Q

what is nuclease

A

enzyme that chops up nucleotides

29
Q

what is nucleosome structure

A

8 histone molecules and the core with DNA wrapped around the histones (146 bp DNA makes 2 wraps around core)

30
Q

What are the levels of chromatin packing from smallest to largest

A

nucleosomes, fibers, looped domains, hectochromatin, highly condensed (chromosomes)

31
Q

what are fibers

A

30nm chromatin fibers made of coiled nucleosomes

32
Q

what are looped domains attached to

A

attached to scaffolding proteins

33
Q

what is the difference between hectochromatin and euchromatin

A

hecto is more tightly packed and usually not active. It shows up as dark spots in micrographs

34
Q

What kind of DNA is not present in high amounts in mitochondrial DNA

A

Non-coding DNA

35
Q

What are two ways mitochondrial and plastid DNA is more similar to bacterial DNA

A

Circular DNA and no histones

36
Q

If every cell contains the genes for every protein in the body, how come we don’t make insulin in our elbows

A

the nucleus plays a role in controlling gene expression

37
Q

What is the basic composition of the nuclear envelope

A

composed of two membranes and nuclear pores

38
Q

outer membrane of nuclear envelope

A

continuous with rough ER

39
Q

inner membrane of nuclear envelope

A

chromatin is stuck to it

40
Q

perinuclear space

A

the space in between the membranes of the nuclear envelope

41
Q

how are nuclear pores composed

A

elaborate structure of about 100 proteins

octagonal arrangement

42
Q

what can pass through nuclear pores

A

small water soluble molecules pass unimpeded

larger molecules can pass with approval

43
Q

What are transporters

A

help move molecules out of nuclear pores

44
Q

what things can be moved out by transporters

A

completed mRNA, assembled ribosomal subunits

45
Q

What things are required for import through nuclear pores

A

nuclear localization signal, importin, GTP hydrolysis

46
Q

What things are required for a molecule to be exported through a pore

A

Nuclear export signal, exportin, GTP

47
Q

What is the nuclear localization signal/nuclear export signal

A

structure on molecule that is binding site for importin/exportin

48
Q

What are two primary functions of the nucleus

A

RNA synthesis and ribosomal subunit synthesis

49
Q

What is the nucleolus organizer region

A

region where the nucleoli form

50
Q

what is the NOR comprised of

A

stretch of DNA where multiple copies of the gene for rRNA are located

51
Q

what is created at the site where all the ends of chromosomes with NOR cluster together

A

the nucleolus

Bio 130 (19 decks)

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