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MCAT-BIOLOGY > Molecular Biology-DNA Structure > Flashcards

Molecular Biology-DNA Structure Flashcards

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1
Q

purines

A

G, A: double rings

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2
Q

pyrimidines

A

C, T, U: single rings

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3
Q

nucleoside

A

ribose or deoxyribose with a purine or pyrimidine linked to the 1’ carbon

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4
Q

nucleotides=nucleoside triphosphates

A

phosphate esters of nucleosides, with 1-3 phosphate groups joined to the ribose ring of the 5’ hydroxy group

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5
Q

what is the backbone of DNA?

A

the sugar/phosphate portion, this is the portion of DNA that is invariant

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6
Q

how are nucleotides in the DNA chain?

A

by covalent phosphodiester bonds between the 3’ hydroxy group of one deoxyribose and the 5’ phosphate group of the next deoxyribose

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7
Q

oligonucleotide

A

a polymer of several nucleotides linked together

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8
Q

polynucleotide

A

a polymer of many nucleotides

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9
Q

what’s the convention of writing nucleotide sequence?

A

5’ to 3’

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10
Q

Watson-Crick model

A

cellular DNA is a right-handed double helix held together by hydrogen bonds between bases

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11
Q

A bonds to:

A

T with two hydrogen bonds

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12
Q

G bonds to:

A

C with three hydrogen bonds

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13
Q

two chains of DNA are complementary if:

A

each strand can hydrogen bond when the strands are oriented in an antiparallel fashion

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14
Q

annealing/hybridization

A

the binding of two complementary strands of DNA into a double-stranded structure

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15
Q

melting/denaturation

A

the separation of DNA strands

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16
Q

right-handed double helix

A

corkscrews in a clockwise motion

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17
Q

what stabilizes the double helix?

A

van der Waals interactions between the bases stacked upon each other

18
Q

genome

A

the sum total of an organism’s genetic information

19
Q

chromosome

A

each piece of ds-DNA

20
Q

what composes prokaryotic (bacterial) genomes?

A

a single circular chromosome

21
Q

is there a correlation between genome size and evolutionary sophistication?

A

no

22
Q

DNA gyrase

A

an enzyme in prokaryotes that uses ATP energy to twist the gigantic circular molecule to make it more compact and sturdy; breaks the DNA and twists the two sides of the circle around each circle to result in a twisted circle composed of ds-DNA to create supercoils

23
Q

supercoil

A

coils of a structure that is already coiled

24
Q

how is eukaryotic DNA packaged?

A

wrapped around globular proteins (histones) and further compacted/condensed

25
Q

nucleosome

A

“beads” of DNA wrapped around an octamer of histomes

26
Q

chromatin

A

fully packed DNA, composed of closely stacked nucleosomes

27
Q

heterochromatin

A

darker and denser regions of chromosomes; rich in repeats

28
Q

euchromatin

A

less dense region of chromosomes

29
Q

density of DNA indicates:

A

extent of coiling or compactness, patterns are constant and heritable

30
Q

lighter/less dense regions have:

A

higher transcription rates and higher gene activity because loose packing=DNA more accessible to enzymes and proteins

31
Q

centromere

A

the region of the chromosome to which spindle fibres attach during cell division

32
Q

kinetochores

A

multiprotein complexes that act as anchor attachment sites for spindle fibers

33
Q

what are centromeres made of?

A

heterochromatin and repetitive DNA sequences

34
Q

centromere position defines the ratio between:

A

the p and q arm

35
Q

p arm

A

short

36
Q

q arm

A

long

37
Q

what are the four centromere positions?

A

metacentric, submetacentric, acrocentric, telocentric

38
Q

telomeres

A

the ends of linear chromosomes, distinct nucleotide sequences repeated 50-hundreds of times

39
Q

what is the typical telomere sequence in vertebrates?

A

5’-TTAGGG-3’ (guanine rich)

40
Q

specialized telomere caps

A

distinguish telomeres from double-stranded breaks (because telomeres can be single or double-stranded) and prevents activation of repair pathways

41
Q

what is the function of telomeres?

A

to prevent chromosome deterioration and also prevent fusion with neighbouring chromosomes

42
Q

how come prokaryotes do not have telomeres?

A

because circular DNA has no “end”

MCAT-BIOLOGY (17 decks)

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