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Chapter 10: Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What did Archibald Garrod find?

A

that rare inherited diseases (single gene traits) were due to defects in specific steps of metabolic pathways; correlated one gene with the production of one enzyme

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2
Q

What is Alkaptonuria (black urine disease) due to? Who discovered this?

A

due to build-up of a chemical intermediate of the metabolism of tyrosine

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3
Q

one gene encodes for ________ ; why?

A

one-polypeptide; Each gene encodes a piece of a protien

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4
Q

What did Beadle and Tatum do?

A

used Neurospora (bread mold) to test hypothesis that specific gene expression correlates with specific enzyme activity

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5
Q

What is neurospora?

A

a simple organism that is haploid for most of its life cycle; all alleles are expressed as phenotypes

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6
Q

How did Beadle and Tatum run their experience?

A

Treated wild-type Neurospora with mutagens and isolated mutant strains that needed specific nutrient supplements to grow

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7
Q

Conclusions of Beadle to Tatum’s Discoveries

A

for each mutant strain, the addition of just one compound supported growth; each mutation caused a defect in only one enzyme in a metabolic pathway

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8
Q

Tatum and Beadle; what did having three different arg mutant strains mean?

A

could have mutations in the same gene – or in different genes that governed steps of a biosynthetic pathway

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9
Q

What was the nutrient path discovered by Tatum and Beadle

A

Precursor –> Ornithine –> citrulline –> arginine

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10
Q

Gene expression to form a specific polypeptide occurs in two steps:

A

transcription and translation

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11
Q

transcription

A

copies information from a DNA sequence (a gene) to a complementary RNA sequence

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12
Q

translation

A

converts RNA sequence to amino acid sequence of a polypeptide

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13
Q

What is the central dogma of molecular biology?

A

transcription and translation

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14
Q

What separates transcription and translation in eukaryotes?

A

the nuclear envelope

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15
Q

Where is the site of transctiption in eukaryotes? translation? What is the intermediate messenger

A

DNA is in the nucleus which is the site of transcription
Ribosomes in the cytoplasm (ER) are the site of translation
mRNA is the intermediate messenger

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16
Q

Where does translation occur in prokaryotes?

A

on growing mRNA

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17
Q

How does RNA differ from DNA?

A
  • contains uracil instead of thymine
    -the sugar is ribose
    -usually differs by a single polynucleotide strand
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18
Q

What are the three kinds of RNA in protein synthesis? How are they made?

A

Messenger RNA, Transfer RNA, RIbosomal RNA
All types are made by transcription

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19
Q

Messenger RNA

A

mRNA; carries a copy of a DNA sequence to the site of protein synthesis at the ribosome; has information for the order of amino acids in a protein

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20
Q

Transfer RNA

A

tRNA; carries amino acids for polypeptide assembly; decodes the information in mRNA; does not hold genetic information for making the protein

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21
Q

Ribosomal RNA

A

rRNA; catalyzes peptide bonds and provides structure
does not hold genetic information for making the protein

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22
Q

What does the shape of tRNA result from? What is always at the amino acid attachment side?

A

The 3D structure results from base pairing (hydrogen bonding) within the molecule; always has CCA on the 3’ attachment side

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23
Q

Where is the location of each RNA types activity?

A

All are in the cytoplasm; rRNA is the ribosomes in the cytoplasm

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24
Q

What does RNA polymerases do?

A

catalyze the synthesis of RNA from a DNA template

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25
Q

RNA polymerases and DNA polymerases are both processive. What does that mean?

A

a single enzyme-template binding results in polymerization of hundreds of RNA bases

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26
Q

Where can RNA polymerases add new nucleotides?

A

It can only add new nucleotides to the 3’ end of a growing strand

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27
Q

What are the differences between DNA polymerases and RNA polymerases

A

-RNA polymerases can initiate synthesis without an existing 3’-OH group, so do not need primers
-RNA polymerases lack a proofreading function

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28
Q

What are the components of transcription

A

-DNA template for base pairings – one of the two strands
-nuceloside triphosphates (Atp, Gtp, Ctp, Utp) as substrates
-An RNA polymerase enzyme
-transcription factors (eukaryotes only)

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29
Q

What are the three phases of transcription

A

Initiation, elongation, termination

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30
Q

Initiation

A

requires a promoter – a special sequence of DNA – that RNA polymerase binds to. The promoter directs the RNA polymerase to where it should start and in which direction to transcribe

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31
Q

Part of each promoter is the ____________ of transcription

A

initiation site

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32
Q

Elongation

A

RNA polymerase unwinds DNA about 10 base pairs at a time; reads template in 3’ to 5’ direction

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33
Q

Where are nucleotides added in elongation? What is this relative to the DNA strand?

A

Antiparallel to the template DNA strand
Added to the 3’ end

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34
Q

Termination

A

specified by a base sequence in DNA that destabilizes the transcription complex

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35
Q

What are a few examples of modes of termination

A

-the transcript falls away from the RNA polymerase and DNA template
-helper protein pulls away the transcript

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36
Q

The _____ of a gene orients the start site and direction of transcription of DNA into RNA

A

promoter region

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37
Q

The DNA template strand is transcribed _____ by RNA polymerase to produce a _______ transcript (or _____)

A

3’ to 5’
5’ to 3’
pre-mRNA

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38
Q

What is an intron? Exons?

A

Introns are transcribed regions that are removed from the pre-mRNA prior to nuclear export; Exons remain

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39
Q

T/F All transcripts of a gene have the same initiation site, or the same exon/intron structure

A

F; not all transcripts have the same

40
Q

Eukaryotic genes may have noncoding sequenes, which are called ______

A

introns

41
Q

Where do introns appear? Where are they removed?

A

appear in the primary mRNA transcript and are removed in the nucleus

42
Q

Where are the coding sequences contained after introns are removed

A

contained in the exons that remain

43
Q

What does the spliceosome do?

A

cuts pre-mRNA, releases introns, and splices exons together to produce mature mRNA

44
Q

RNA splicing _______ and _____

A

removes introns and splices exons together

45
Q

Where is newly transcribed (post-splicing) pre-mRNA bound? By what?

A

At the ends
By snRNPs (small nuclear ribonucleoprotein particles)

46
Q

What are consensus sequenes

A

short sequences at exon/intron junctions; where snRNPs bind and near the 3’ end of the intron

47
Q

T/F in the eukaryotic nucleus, in the addition to intron removal, one end of pre-mRNA is modified

A

F; both ends are modified. A G cap at the 5’ end and a Poly A tail at the 3’ end

48
Q

What is a G cap

A

modified guanosine triphosphate
added to the 5’ end to facilitate mRNA binding to the ribosome and to protect mRNA from being degraded by ribonucleases

49
Q

What is a poly A tail

A

Added to the 3’ end
-An AAUAAA sequence after the last codon which is a signal for an enzyme to cut the pre-mRNA; then another enzyme adds 100 to 300 adenines (the tail)
- may assist in export from nucleus; important for the stability of mRNA

50
Q

What does UTR stand for?

A

Untranslated Region

51
Q

T/F the genetic code is ambiguous and not redundant

A

F; the genetic code is redundant (more than one codon creates an amino acid) but not ambiguous (each coding only signals for one amino acid)

52
Q

Somatic mutations

A

occur in somatic cells – passed on by mitosis but not to sexually produced offspring

53
Q

Germ line mutations

A

occur in germ line cells, the cells that give rise to gametes; a gamete passes a mutation on at fertilization

54
Q

silent mutations

A

do not change the polypeptide sequence or protein function

55
Q

loss of function mutation

A

affect protein function and may lead to structural proteins or enzymes that no longer work - almost always recessive

56
Q

Gain of function mutations

A

lead to a protien with altered function

57
Q

conditional mutations

A

cause phenotypes under restrictive conditions, but are not detectable under permissive conditions

58
Q

point mutations

A

results from the gain, loss, or substitution of a single basepair of DNA; can be silent or alter the sequence of the polypeptide

59
Q

A missense point mutation at a nonsynonymous site ___________

A

changes a single amino acid

60
Q

A nonsense point mutation shortens polypeptide by causing ___________

A

premature termination of translation

61
Q

loss of stop mutation

A

causes read-through translation to a new stop codon

62
Q

frame-shift

A

changes reading frame by adding or deleting bases

63
Q

tRNA

A

the adapter molecules associates information in mRNA codons with specific amino acids

64
Q

tRNA functions

A

binds to an amino acid, and is then “charged”, associates with mRNA molecules, interacts with ribosomes

65
Q

Anticodon

A

At the midpoint of the tRNA sequence; The site of base pairing between tRNA and mRNA

66
Q

What does the 3D conformation of tRNA result from?

A

base pairing – hydrogen bonding – within the molecules

67
Q

When end of the tRNA is the amino acid attachment site? How do they attach?

A

3’ end; binds covalently

68
Q

What energy source is needed to charge a tRNA molecule?

A

ATP

69
Q

What enzymes charge tRNA? What is its specificity? What is it’s three-part active site bind to?

A

aminoacyl-tRNA; highly specific for one amino acid and it’s corresponding tRNA; binds to a specific amino acid, a specific tRNA, and ATP

70
Q

What is wobble?

A

specificity for the. base at the 3’ end of the codon is not always observed; allows cells to produce fewer tRNA species, but does NOT create any ambiguity in the genetic code

71
Q

What does the ribosomes do?

A

its the workbench; holds mRNA and charged tRNA in the correct positions to allow assembly of polypeptide chain

72
Q

What are the subunits of a ribosome?

A

Large: 3 molecules of rRNA
Small: 1 molecule of rRNA

73
Q

What are the three tRNA binding sites in the large subunit?

A

A (amino acid) site, P (polypeptide) site, E (exit) site

74
Q

What are the three stags of translation?

A

Initiation, Elongation, Termination

75
Q

What is RNA initiation

A

formation of the initiation complex – a charged tRNA and small ribosomal subunit, both bound to mRNA

76
Q

What is RNA Elongation

A

charged tRNA enters A site, large subunit acts as peptidyl transferase

77
Q

What is RNA Termination

A

a stop codon enters the A site of the ribosome

78
Q

How do prokaryotes initiate translation?

A

rRNA binds to mRNA recognition site “upstream” of the start codon

79
Q

How do eukaryotes initiate translation?

A

small subunit of a ribosome binds to the 5’ cap on the mRNA and moves until it reaches the start codon

80
Q

What is the mRNA start codon

A

AUG

81
Q

What is the N-terminus

A

the first amino acid after the mRNA start codon (methionine) which may be removed after translation

82
Q

Where does the charged tRNA enter the large subunit? Where do the following ones enter? How do they interact?

A

The first enters the P site; the second enters the A site.
The bond breaks between the tRNA in the P site and it’s amino acid; that amino acid forms a peptide bond with the amino acid carried by the tRNA in the A site

83
Q

What protiens assist RNA elongation?

A

elongation factors

84
Q

What happens to tRNA after it breaks its bond with it’s amino acid

A

it moves to the E-site where it dissociates from the ribosome; it can become charged again

85
Q

When does RNA translation end?

A

when a stop codon enters the A site; this codon binds a protein release factor that allows hydrolysis of the bond between the polypeptide chain and tRNA on the P site

86
Q

What is the last amino acid added to a polypeptide chain in RNA translation?

A

C terminus

87
Q

Where are ribsomes located in a eukaryotic cell? Where is polypeptide chains released after termination?

A

Located in the membrane of the RER; the chain is released into the lumen of the RER

88
Q

What are the three types of post-translational modifications?

A

Phosphorylation, Glycosylation, and Proteolysis

89
Q

What is phosphorylation?

A

Adding phosphate groups to the polypeptide chain in post-translational processing to alter the shape of the protien

90
Q

What is glycosylation?

A

Adding sugars to the polypeptide chain in post-translational processing that are important for targeting and recognition

91
Q

What is proteolysis

A

Cleaving the polypeptide chain in post-translational processing to allow the fragments to fold into different shapes

92
Q

What are the differences betw4een RNA transcription/ translation in Prokaryotes and Eukaryotes

A

In prokaryotes, both processes occur at the same time in the cytoplasm; In eukaryotes transcription occurs first in the nucleus then translation occurs in the cytosol

93
Q

What are the differences between gene structure for Prokaryotes and Eukaryotes

A

In prokaryotes, DNA sequence is not usually interrupted by introns; in Eukaryotes, transcribed regions (exons) are often interrupted by non-coding introns

94
Q

What are the difference between the modification of mRNA after transcription but before translation for Eukaryotes and Prokaryotes

A

In prokaryotes, there is usually no modification; In eukaryotes, introns are spliced out of pre-mRNA, and the 5’cap and 3’ poly-A tail are added to mRNA.

95
Q

What are the differences between translation initiation in prokaryotes and eukaryotes

A

In prokaryotes, the small subunit of the ribosomes associates with mRNA at the Shine-Dalgarno sequence; in Eukaryotes, the small subunit of ribosome binds at the 5’ end of mRNa and moves to start codon

Biology (12 decks)

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