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Biology 243 > Topic 1B > Flashcards

Topic 1B Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

nucleotide

A

a constituent of nucleic acids, consisting of a 5-carbon sugar, a nitrogen-containing base, and one or more phosphate groups

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2
Q

explain the purposes and components of a nucleotide:

A

the 5-carbon sugars and phosphate forms the backbone of the molecule, the nitrogen base sticks out and gives each nucleotide its chemical identity

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3
Q

deoxyribose

A

the sugar in DNA

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4
Q

what happens to the hydroxyl group at cellular pH (7)?

A

the free hydroxyl groups become negatively charged by losing a proton (the two oxygen atoms have a negative charge)

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5
Q

purines

A

double-ring structures

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6
Q

pyrimidines

A

single-ring structures

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7
Q

what are the purines?

A

adenine (A) and guanine (G)

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8
Q

what are the pyrimidines?

A

thymine (T) and cytosine (C)

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9
Q

nucleoside

A

a molecule consisting of a 5-carbon sugar and a base

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10
Q

what are the nitrogen containing bases?

A

A, G, (purines) and T, C, (pyrimidines)

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11
Q

what molecule is used to form nucleotide polymers (DNA, RNA)?

A

nucleoside triphosphate (nucleosides-sugar+base and three phosphate groups)

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12
Q

phosphodiester bond

A

a bond that forms when a phosphate group in one nucleotide is covalently joined to the sugar unit in another nucleotide. Phosphodiester bonds are relatively stable and form the backbone of a DNA strand

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13
Q

polarity

A

an asymmetry such that one end of a structure differs from the other- caused in a strand of DNA by the phosphodiester linkages

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14
Q

5’ end

A

the end of a nucleic acid strand containing a free 5’ phosphate group (top)

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15
Q

3’ end

A

the end of a nucleic acid strand that carries a free 3’ hydroxyl (bottom)

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16
Q

in the double helix model, where are the components of the nucleotides located?

A

the sugar-phosphate backbones point wind outwards with the bases pointing inward

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17
Q

major groove

A

the larger of two uneven grooves on the outside of a DNA duplex

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18
Q

minor groove

A

the smaller of two unequal grooves to the outside of a DNA duplex

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19
Q

why are the grooves important?

A

proteins that interact with DNA often recognize a particular sequence of bases by making contact with the bases via either/both the major/minor grooves

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20
Q

antiparallel

A

oriented in opposite directions; the strands in a DNA duplex are antiparallel

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21
Q

complementary

A

describes the relationship of purine and pyrimidine bases, in which the base A pairs only with T and G pairs only with C

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22
Q

what explains the specificity of complementary base pairs?

A

hydrogen bonds (A-T has 2) and (G-C has 3)

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23
Q

what contributes to the stability of the DNA double helix

A

the total number of hydrogen bonds between base pairs and base stacking

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24
Q

base stacking

A

stabilizing hydrophobic interactions between bases in the same strand of DNA

25
Q

brief explanation for how replication of DNA occurs:

A

strands unwind and each strand serves as a “parent” or template to create daughter strands

26
Q

supercoil

A

a coil of coils; a circular molecule of DNA can coil upon itself to form a supercoil-seen in prokaryotes

27
Q

topoisomerase

A

any one of a class of enzymes that regulates the supercoiling of DNA by cleaving one or both strands of the DNA double helix, and later repairing the break

28
Q

how are DNA molecules shaped in eukaryotic cells?

A

linearly

29
Q

chromosome

A

in eukaryotes, the physical structure in which DNA in the nucleus is packaged

30
Q

chromatin

A

a complex of DNA, RNA, and proteins (histones) that gives chromosomes their structure; chromatin fibres are either 30 nm in diameter or, in a relaxed state, 10 nm

31
Q

evolutionarily conserved

A

characteristics that persist relatively unchanged through diversification of a group of organisms and therefore remain similar in related species

32
Q

why do histone proteins (found in all eukaryotes) interact with double-stranded DNA without regard to sequence?

A

because the proteins are evolutionarily conserved

33
Q

the more distantly related two organisms that share conserved sequences…

A

the more highly conserved the sequence is

34
Q

the genomes of ALL organisms are ______ relative to the size of the cell

A

large

35
Q

describe bacterial genomes:

A

circular, the DNA double helix is under-wound (fewer turns in going around the circle)-caused by topoisomerase II

36
Q

topoisomerase II

A

an enzyme that breaks a DNA double helix, rotates the ends, and seals the break

37
Q

what does under-winding create on the DNA molecule

A

strain (relieved by formation of supercoils)

38
Q

what are supercoils that result from under-winding called?

A

negative supercoils

39
Q

what are supercoils that result from over-winding called?

A

positive supercoils

40
Q

what kind of supercoils form in DNA in most organisms?

A

negative supercoils

41
Q

nucleoid

A

in prokaryotes, a cell structure with multiple loops formed from supercoils of DNA

42
Q

how is DNA packaged in eukaryotes?

A

the linear DNA forms a single chromosome which is packaged with histone proteins into a complex called chromatin

43
Q

nucleosome

A

a beadlike repeating unit of histone proteins wrapped with DNA making up the 10-nm chromatin fibre

44
Q

how many histone proteins are in a nucleosome

A

8 (2 of each-H2A, H2B, H3, and H4)

45
Q

describe the components of a histone protein:

A

amino acids:lysine and arginine, with positive charges

46
Q

10-nm fibre

A

a relaxed 30-nm chromatin fibre, the state of the chromatin fibre in regions of the nucleus where transcription is currently taking place

47
Q

30-nm fibre

A

a chromosomal conformation created by the folding of the nucleosome fibre of DNA and histones

48
Q

chromosome condensation

A

the progressive coiling of the chromatin fibre, an active, energy-consuming process requiring the participation of several types of proteins

49
Q

scaffold

A

a supporting protein structure in a metaphase chromosome-how DNA spreads out without histones

50
Q

homologous chromosomes

A

pairs of chromosomes, matching in size and appearance, that carry the same set of genes; one of each pair was received from the mother, the other from the father

51
Q

at what stage are chromosomes in chromosome paintings?

A

metaphase of mitosis

52
Q

karyotype

A

a standard arrangement of chromosomes, showing the number and shapes of the chromosomes representative of a species

53
Q

Since the DNA in each pair of homologous chromosomes is different from that in any other pair of homologous chromosomes….

A

a particular labeled DNA fragment hybridizes (marks) only with the two homologs of one chromosomes

54
Q

what is the relationship between chromosome number and genome size?

A

there is no relationship

55
Q

because each type of organelle has its own DNA, this means that…

A

eukaryotic cells will have multiple genomes

56
Q

nuclear genome

A

in eukaryotic cells, the DNA in the chromosomes

57
Q

mitochondrial genome

A

in eukaryotic cells, the DNA in the mitochondria

58
Q

chloroplast genome

A

in photosynthetic eukaryotes, the genome of the chloroplast

59
Q

how is organelle DNA packaged?

A

as a nucleoid rather than a chromosome (similar to bacterial ancestors)-difference between structures of mitochondria/chloroplast nucleoid

Biology 243 (15 decks)

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