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Biochemistry > DNA: Nucleic Acid Structure And function > Flashcards

DNA: Nucleic Acid Structure And function Flashcards

0
Q

Most common nucleic acids are

A

DNA & RNA

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1
Q

Is a macromolecule composed of nucleotide chains. These molecules carry genetic information within cells. Are universal in living things, and are also found in viruses.

A

Nucleic acid

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2
Q

Are compounds are structurally similar to naturally occurring RNA & DNA, used as a research tool in molecular biology and/or as cure in medicine

A

Nucleic acid analogues

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3
Q

Is a polymeric molecule composed of 4 types of monomeric units that contains the genetic information of an organism.

A

DNA

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4
Q

The discovery that genetic formation is coded along the length of polymeric molecule composed of only four types of _____________.

A

Monomeric units

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5
Q

The genetic code in DNA depends on how ______ & ______ are arranged in a ______.

A

Purines & Pyrimidines. DNA strand.

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6
Q

The DNA structure was proposed by whom. They were able to form a model of double-stranded DNA in helical form held together by ________.

A

James Watson & Francis Crick. Hydrogen bonds.

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7
Q

One turn of B-DNA includes ________. The ________ of the double helix is indicated by the vertical cord.

A

10 base pairs. Central axis.

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8
Q

Occurs where the backbones are far apart

A

Major groove

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9
Q

Occurs where they are close together

A

Minor groove

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10
Q

In major and minor grooves, certain protein binds to DNA to alter its structure or regulate ______(copying DNA to RNA) or _______(copying DNA to DNA)

A

Transcription. Replication.

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11
Q

In major and minor grooves, It is easier for DNA binding proteins to interact with these bases (the internal parts of the DNA molecule) on the _________ side because the _______ are not in the way.

A

Major groove. Backbones.

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12
Q

The purine and pyrimidine bases G, C, T & A are held together by a __________ backbone between 2’ deoxyribosyl moieties attached to the nucleobases by an _________.

A

Phosphodiester. N-glycosylic bond.

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13
Q

In major and minor grooves, The backbone has _______. Convention dictates that a single stranded DNA sequence is written in the __ to __ direction.

A

Polarity. 5’ to 3’.

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14
Q

The common DNA form is said to be ______ because as one looks down the double helix, the base residues from a ________ in a _______ direction.

A

Right-handed. Spiral. Clockwise.

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15
Q

The two strands of the double-helical molecule, each of which possesses a polarity, are ________; ie, on strand runs in the 5’ to 3’ direction and the other in the 3’ to 5’ direction.

A

Antiparallel

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16
Q

the strand that is copied during nucleic acid synthesis.

A

Template/non-coding strand

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17
Q

Matches the RNA transcript that encodes the protein ( but containing _______ in place of thymine)

A

Coding strand. Uracil.

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18
Q

2 DNA strands

A

Coding strand and Non-coding/Template strand

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19
Q

In RNA strand segment, Double stranded DNA exists in at least

A

Six forms: A-E and Z

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20
Q

In RNA strand segment, is usually found under physiologic conditions (low salt, high degree of hydration)

A

B form

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21
Q

In RNA strand segment: are much more resistant to denaturation, or “melting” than A-T rich regions. This is because three hydrogen bonds hold the __________ to the _________, whereas the other pair, the A-T pair, is held together by ________ only.

A

G-C bonds. Deoxyguanosine nucleotide. Deoxycytidine nucleotide. Two hydrogen bonds.

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22
Q

The double stranded DNA structure can be separated in a solution by

A

Increasing the temp & decreasing the salt concentration

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23
Q

Separated strands of DNA will renature or will reassociate when appropriate physiologic temperature and salt conditions are achieved in a process called

A

Hybridization

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24
Q

In some organisms such as bacteria, bacteriophages, many DNA-containing animal viruses, as well as organelles such as mitochondria, the ends of the DNA molecules are joined to create a closed circle _________. This does not destroy the polarity of molecules, but it eliminates all free ___________.

A

No covalently free ends. 3’ and 5’ hydroxyl and phosphoryl groups.

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25
Q

Closed circles exist in

A

Relaxed/Supercoiled forms

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26
Q

Are formed when the molecule is twisted in the direction opposite from the clockwise turns of the right-handed double helix found in B-DNA. Such DNA is said to be underwound.

A

Negative supercoils

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27
Q

Enzymes that catalyze topologic changes of DNA. Can relax or insert supercoils. Best example is BDG.

A

Topoisomerase

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28
Q

Introduces negative supercoils (or relaxes positive supercoils) using ATP as energy source.

A

DNA gyrase

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29
Q

The ability of gyrase to relax positive supercoils comes into play during

A

DNA replication

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30
Q

Drugs like _______ that inhibit DNA gyrase are used as antibacterial.

A

Quinolones

31
Q

Provides a template for replication and transcription. It is the source of info for protein synthesis. It provides info for inheritance.

A

DNA

32
Q

Complementarity of DNA strands suggest that replication is done in a ___________, where each strand is used to create a new daughter strand.

A

Semi-conservative manner

33
Q

During a round of replication, each of the two strands of DNA is used as a template for synthesis of a new

A

Complementary strand

34
Q

Is a polymer of purine and pyrimidine ribonucleotides linked together by a __________ analogous to those in DNA.

A

Ribonucleic Acid. Phosphodiester bridges.

35
Q

Sugar: Deoxyribose

A

DNA

36
Q

Sugar: Ribose

A

RNA

37
Q

Pyrimidines: cytosine & uracil

A

RNA

38
Q

Strand: double

A

DNA

39
Q

Hydrolysis by alkaline solution: not possible

A

DNA

40
Q

Pyrimidines: cytosine & thymine

A

DNA

41
Q

Strand: single

A

RNA

42
Q

Hydrolysis by alkaline solution: possible

A

RNA

43
Q

Base content: A =/ T & G =/ C

A

RNA

44
Q

Base content: A=T & G=C

A

DNA

45
Q

The ________ with a 5’ to 3’ polarity is complementary to the template strand with its 3’ to 5’ polarity.

A

RNA transcript

46
Q

The sequence in the RNA transcript and its polarity is the same as that in ________, except that the __ of the transcript replaces the __ of the gene.

A

Coding strand. U. T.

47
Q

Serves as template for protein synthesis

A

Messenger RNA

48
Q

For mRNA recognition prior to translation. Stabilizes mRNA.

A

CAP

49
Q

The 5’ terminal of mRNA is “capped” by a _________ that is linked to an adjacent _________ at its 5’-hydroxyl through the three phosphates.

A

7-methylguanosine triphosphate. 2’-O-methyl ribonucleoside.

50
Q

The 3’ end of mRNA has an attached polymer of adenylate residues 20-250 nucleotides in length called

A

Poly (A) Tail

51
Q

In eukaryotic organisms, __________ is the mechanism by which most messenger RNA molecules are terminated at their 3’ ends.

A

Polyadenylation

52
Q

Protects the mRNA molecule from exonucleases and is important for transcription termination, for export of the mRNA from the nucleus, and for translation.

A

Polyadenosine tail

53
Q

Some mRNAs, including those for some _____, do not contain poly(A) tails.

A

Histones

54
Q

Both the mRNA cap and poly(A) tail are added _________ by _______ enzymes.

A

Post transcriptionally. Nontemplate-directed.

55
Q

In mammalian cells, including cells of humans, the mRNA molecules present in the cytoplasm are not RNA products immediately synthesized from the __________.

A

DNA template

56
Q

In mammalian nuclei, the immediate products of gene transcription constitute a

A

Fourth class of RNA molecules

57
Q

Nuclear RNA molecules that are precursors to the mature, fully processed mRNAs.

A

Heterogenous nuclear RNA (hnRNA)

58
Q

Serve as adapters for the translation of mRNA to AA. There are atleast __ species of tRNA in each cell, at least 1 corresponding to each of the 20 AA required for protein synthesis.

A

Transfer RNA (tRNA)

59
Q

Although tRNAs are quite stable in _______, they are somewhat unstable in _______. The opposite is true for mRNAs, which are quite unstable in ________ but generally more stable in _______ organism.

A

Prokaryotes. Eukaryotes. Prokaryotes. Eukaryotic.

60
Q

Allows extensive folding and intra-strand complementarity to generate a secondary structure that appears in two dimensions like a cloverleaf.

A

Primary structure of all tRNA molecules

61
Q

A unit made up of three nucleotides that correspond to the three bases of the codon on the mRNA.

A

Anticodon/Nodoc

62
Q

Each tRNA contains a specific anticodon __________ that can base pair to one or more codons for an AA. Ex: one codon for lysine is AAA; the anticodon of a lysine tRNA might be UUU.

A

Triplet sequence.

63
Q

A cytoplasmic nucleoprotein that acts as the machinery for the synthesis of proteins from mRNA templates.

A

Ribosomal RNA (rRNA)

64
Q

On the ribosomes, the _____ & _____ molecules interact to translate into a specific protein molecule info transcribed from the gene.

A

mRNA and tRNA

65
Q

In ribosomes, larger subunit

A

60s

66
Q

In ribosomes, smaller

A

40s

67
Q

In ribosomes, The 60s subunit contains

A

5s, 5.8s & 28s

68
Q

In ribosomes, The 40s subunit contains a single

A

18s subunit

69
Q

In ribosomes, all rRNA molecules except the ______ are processed from a single ___ precursor RNA molecule in the nucleolus.

A

5srRNA. 45s.

70
Q

In ribosomes, it is independently transcribed

A

5sRNA

71
Q

Ribosomal RNA molecules are packaged in the

A

Nucleolus

72
Q

Is the target of several clinically relevant antibiotics: Erythromycin & etc.

A

rRNA

73
Q

Is the most conserved(least variable) gene in all cells. For this reason, genes that encode the rRNA (rDNA) are sequenced to identify an organism’s _______, calculate related groups, and estimate rates of species divergence.

A

rRNA. Taxonomic group.

74
Q

Found within the nucleus of eukaryotic cells. They are involved in a variety of important processes such as ________, regulation of transcription factors and maintaining telomeres. These elements are rich in ________ content.

A

Small nuclear RNA (snRNA). RNA splicing. Uridine content.

75
Q

Region of highly repetitive DNA at the end of a linear chromosome.

A

Telomeres

76
Q

Removal of introns from hnRNA

A

RNA splicing

Biochemistry (20 decks)

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