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MCAT Biology > Ch. 4 Molecular Biology > Flashcards

Ch. 4 Molecular Biology Flashcards

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1
Q

5’ cap

A

A methylated guanine nucelotide added to the 5’ end of eukaryotic mRNA. The cap is necessary to initiate translation of the mRNA.

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2
Q

activator proteins

A

Proteins that bind to enhancer sequences in eukaryotes to increase transcription.

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3
Q

adenine

A

One of the four aromatic bases found in DNA and RNA; also a component of ATP, NADH, and FADH2. Adenine is a purine; it pairs with thymine (in DNA) and with uracil (in RNA).

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4
Q

amino acid acceptor site

A

The 3’ end of a tRNA molecule that binds an amino acid. The nucleotide sequence at this end is CCA.

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5
Q

aminoacyl tRNA

A

A tRNA with an amino acid attached. This is made by an aminoacyl-tRNA synthetase, and enzyme that is specific to the amino acid being attached.

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6
Q

anabolism

A

The process of building complex structures out of simpler precursors (e.g. synthesizing proteins from amino acids)

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7
Q

anticodon

A

A sequence of three nucleotides (found in the anticodon loop of tRNA) that is complementary to a specific codon in mRNA. The codon to which the anticodon is complementary specifies the amino acid that is carried by that tRNA.

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8
Q

A site

A

Aminoacyl-tRNA site; the site on a ribosome where a new amino acid is added to a growing peptide.

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9
Q

centromere

A

A structure near the middle of the eukaryotic chromosomes to which the fibers of the mitotic spindle attach during cell division

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10
Q

chaperones

A

A family of proteins that assists in the folding of other proteins

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11
Q

chromosome

A

A single piece of double-stranded DNA; part of the genome of an organism. Prokaryotes have circular chromosomes and eukaryotes have linear chromosomes.

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12
Q

codon

A

A group of three nucleotides that is specific for a particular amino acid, or that specifies “stop translating”

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13
Q

copy-number variation

A

Structural variations in the genome that lead to different copies of certain sections of the DNA, due to duplication of those sections or deletions of those sections

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14
Q

cytosine

A

One of the four aromatic bases found in DNA and RNA. Cytosine is a pyrimidine; it pairs with guanine.

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15
Q

DNA polymerase

A

Also called DNA pol, this is the enzyme that replicates DNA. Eukaryotes and prokaryotes have different versions of this enzyme.

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16
Q

downstream

A

Toward the 3’ end of an RNA transcript (the 3’ end of the DNA coding strand). Stop codons and (in eukaryotes) the poly-A tail are found “downstream.”

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17
Q

elongation factors

A

Proteins that assist with peptide bond formation during eukaryotic translation

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18
Q

epigenetics

A

Changes in gene expression that are not due to mutations, but are long-term and heritable (e.g. DNA methylation, chromatin remodeling, and RNA interference).

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19
Q

exon

A

A nucleotide sequence in RNA that contains protein-coding information. Exons are typically separated by introns (intervening sequences) that are spliced out prior to translation

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20
Q

formylmethionine (fMet)

A

A modified methionine used as the first amino acid in all prokaryotic proteins

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21
Q

frameshift mutation

A

A mutation caused by an insertion or deletion of base pairs in a gene sequence in DNA such that the reading frame of the gene (and thus the amino acid sequence of the protein) is altered.

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22
Q

gene

A

A portion of DNA that codes for some product, usually a protein, including all regulatory sequences. Some genes cod for rRNA and tRNA, which are not translated.

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23
Q

genetic code

A

The “language” of molecular biology that specifies which amino acid corresponds to which three-nucleotide group (a codon)

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24
Q

genome

A

All the genetic information in an organism, all of an organism’s chromosomes.

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25
Q

guanine

A

One of the four aromatic bases found in DNA and RNA. Is a purine; it pairs with cytosine.

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26
Q

gyrase (DNA gyrase)

A

A prokaryotic enzyme used to twist the single circular chromosome of prokaryotes upon itself to form supercoils. Supercoiling helps to compact prokaryotic DNA and make it sturdier.

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27
Q

helicase

A

An enzyme that unwinds the double helix of DNA and separates the DNA strands in preparation for DNA replication.

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28
Q

hemizygous gene

A

A gene appearing in a single copy in diploid organisms, e.g. X-linked genes in human males

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29
Q

heterochromatin

A

Densely packed, tightly coiled DNA, generally inactive (i.e., not being transcribed).

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30
Q

hnRNA

A

Hetergeneous nucelar RNA; the primary transcript made in eukaryotes before splicing

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31
Q

imprinting

A

Physical change to a gene on DNA, such as methylation or histone binding, that renders it inactive, so that only one allele of the gene is expressed

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32
Q

inducible system

A

A system (set of genes) where the expression of those genes is stimulated by an abundance of substrate (e.gf., the lac operon)

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33
Q

initiation factors

A

Eukaryotic proteins that assemble in a complex to begin translation.

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34
Q

intron

A

A nucleotide sequence that intervenes between protein-coding sequences. In DNA, these intervening sequences typically contain regulatory sequences, however, in RNA they are simple spliced out to form the mature (translated) transcript.

35
Q

Kinetochores

A

Multiprotein complexes that attach the spindle fibers to the centromere of a chromosome.

36
Q

lac operon

A

A set of genes for the enzymes necessary to import and digest lactose, under the control of a single promoter, whose expression is stimulated by the presence of lactose (this is an inducible system).

37
Q

lagging strand

A

The newly forming daughter strand of DNA that is replicated in a discontinuous fashion, via Okazaki fragments that will ultimately be ligated together; the daughter strand that is replicated in the opposite direction that the parental DNA is unwinding.

38
Q

leading strand

A

The newly forming daughter strand of DNA that is replicated in a continuous fashion; the daughter strand that is replicated in the same direction that the parental DNA is unwinding.

39
Q

ligase

A

An enzyme that connects two fragments of DNA to make a single fragment; also called DNA ligase. This enzyme is used during DNA replication and is also used in recombinant DNA research.

40
Q

missense mutation

A

A point mutation in which a codon that specifies an amino acid is mutated into a codon that specifies a different amino acid.

41
Q

monocistronic mRNA

A

mRNA that codes for a single type of protein, such as is found in eukaryotic cells.

42
Q

mRNA

A

Messenger RNA; the type of RNA that is read by a ribosome to synthesize protein.

43
Q

mRNA surveillance

A

The monitoring of mRNA transcripts to eliminate those that are defective (e.g., have no stop codon, have premature stop codons, or that have somehow stalled in translation).

44
Q

ncRNA (non-coding RNA)

A

RNA that is not translated into protein, including tRNA, rRNA, snRNA, miRNA, etc.

45
Q

nonsense mutation

A

A point mutation in which a codon that specifies an amino acid is mutated into a stop (nonsense) codon.

46
Q

nucleoside

A

A structure of a ribose molecule linked to one of the aromatic bases. In a deoxynucleoside, the ribose is replaced with deoxyribose.

47
Q

nucleosome

A

A structure composed of two coils of DNA wrapped around an octet of histone proteins. The nucelosome is the primary form of packaging of eukaryotic DNA.

48
Q

nucleotide

A

A nuceloside with one or more phosphate groups attached. Nucleoside triphosphates (NTPs) are teh building blocks of RNA and are also used as energy molecules, especially ATP. Deoxynucleoside triphosphates (dNTPs) are the building blocks of DNA; in these molecules, the ribose is replaced with deoxyribose.

49
Q

Okazaki fragments

A

Small fragments DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

50
Q

origin of replication

A

The specific location on a DNA strand where replication begins. Prokaryotes typically have a single origin of replication, while eukaryotes have several per chromosome.

51
Q

peptidyl transferase

A

The enzymatic activity of the ribosome that catalyzes the formation of a peptide bond between amino acids. It is thought that the rRNA of the ribosome possesses the peptidyl transferase activity.

52
Q

point mutation

A

A type of mutation in DNA where a single base is substituted for another.

53
Q

poly-A tail

A

A string of several hundred adenine nucleotides added to the 3’ end of eukaryotic mRNA

54
Q

polycistronic mRNA

A

mRNA that codes for several different proteins by utilizing different reading frames, nested genes, etc. Polycistronic mRNA is a characteristic of prokaryotes.

55
Q

primase

A

An RNA polymerase that creates a primer (made of RNA) to initiate DNA replication. DNA pol binds to the primer and elongates it.

56
Q

promoter

A

The sequence of nucleotides on a chromosome that activates RNA polymerase so that transcription can take place. The promoter is found upstream of the start site, the location where transcription actually begins.

57
Q

P site

A

Peptidyl-tRNA site; the site on a ribosome where the growing peptide (attached to a tRNA) is found during translation.

58
Q

purine bases

A

Aromatic bases found in DNA and RNA that are derived from purine. They have a double ring structure and include adenine and guanine.

59
Q

pyrimidine bases

A

Aromatic bases found in DNA and RNA that have a single-ring structure. They include cytosine, thymine, and uracil.

60
Q

release factor

A

A cytoplasmic protein that binds to a stop codon when it appears in the A-site of the ribosome. Release factors modify the peptidyl transference activity of the ribosome, such that a water molecule is added to the end of the completed protein. This releases the finished protein from the final tRNA, and allows the ribosome subunits and mRNA to dissociate.

61
Q

replication

A

The duplication of DNA

62
Q

replication fork(s)

A

The site(s) where the parental DNA double helix unwinds during replication.

63
Q

replication bubbles

A

Multiple sites of replication found on large, linear eukaryotic chromosomes.

64
Q

repressible system

A

A system (set of genes) where the expression of those genes in inhibited by the gene product (e.g., the trp operon).

65
Q

repressor

A

A regulatory protein that binds DNA at a specific nucleotide sequence (sometimes known as the operator) to prevent transcription of downstream genes.

66
Q

ribosome

A

A structural made of two protein subunits and rRNA; this is the site of protein synthesis (translation) in a cell. Prokayotic ribosomes (also known as 70S ribosomes) are smaller than eukaryotic ribosomes (80S ribosomes). The S value refers to the sedimentation rate during centrifugation.

67
Q

RNA interference (RNAi)

A

Small non-coding RNAs that bind to mRNAs, these double-stranded RNAs are then degraded and gene expression is reduced.

68
Q

RNA polymerase

A

An enzyme that transcribes RNA. Prokaryotes have a single RNA pol, while eukaryotes have three; in eukaryotes, RNA pol I transcribes tRNA, RNA pol II transcribes mRNA, and RNA pol III transcribes tRNA.

69
Q

RNA translocation

A

The movement in the retina of the eye that respond to dim light and provide us with black and white vision.

70
Q

rRNA

A

Ribosomal RNA; the type of RNA that associates with ribosomal proteins to make a functional ribosome. It is thought that the rRNA has the peptidyl transferase activity.

71
Q

semiconservative replication

A

DNA replication. Each of the parental strands is read to make a complementary daughter strand, thus each new DNA molecule is composed of half the parental molecule paired with a newly synthesized strand.

72
Q

Shine-Dalgarno sequence

A

The prokaryotic ribosome-binding site on mRNA, found 10 nucleotides 5’ to the start codon.

73
Q

silent mutation

A

A point mutation in which a codon that specifies an amino acid is mutated into a new codon that specifies the same amino acid.

74
Q

single nucleotide polymorphisms (SNPs)

A

Variations in a single nucleotide from one person’s DNA gene sequence to another’s. These minor mutations can produce changes in phenotype.

75
Q

single strand binding proteins

A

Proteins that bind to and stabilize the single strands of DNA exposed when helicase unwinds the double helix in preparation for replication.

76
Q

S (synthesis) phase

A

The phase of the cell cycle during which the genome is replicated.

77
Q

spliceosome

A

A complex made of many proteins and several small nuclear RNAs (snRNAs) that assembles around an intron to be spliced out of the primary transcript.

78
Q

splicing

A

One type of eukaryotic mRNA processing in which introns are removed from the primary transcript and exons are ligated together. Splicing off transcripts can be different in different tissues.

79
Q

start site

A

The location on a chromosome where transcription begins.

80
Q

stop codon

A

A group of three nucleotides that does not specify a particular amino acid, but instead serves to notify the ribosome that the protein being translated is complete. The stop codons are UAA, UGA, and UAG. Theey are also known as nonsense codons.

81
Q

tandem repeats

A

Regions of the genome where short sequences of nucleotides are repeated one after the other, anywhere from 3-100 times.

82
Q

telomere

A

A specialized region at the ends of eukaryotic chromosomes that contain several repeats of a particular DNA sequence. These ends are maintained (in some cells) with the help of a special DNA polymerase called telomerase. In cells that lack telomerase, the telomeres slowly degrade with each round of DNA replication; this is thought to contribute to the eventual death of the cell.

83
Q

theta replication

A

DNA replication in prokaryotes, so named because as replication proceeds around the single, circular chromosome, it takes on the appearance of the Greek letter theta.

84
Q

thymine

A

One of the four aromatic based found in DNA. Tymine

MCAT Biology (2 decks)

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