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Genetics Final Exam > Chapter 9 > Flashcards

Chapter 9 Flashcards

(42 cards)

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1
Q

Gene Expression

A

RNA transcribes DNA to RNA transcript
Ribosomes translate mRNA sequence to synthesize polypeptide
Follows genetic code

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2
Q

Codon

A

set of 3 nucleotides = codon = 1 amino acid

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3
Q

Frederick Sanger

A

Made Sanger sequencing
replaced by next generation sequencing methods, still remains widely used for small-scale projects

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4
Q

Charles Yanofsky

A

Genes nucleotide is colinear
Generated large number of trpA mutants
fine structure genetic map of trpA based on intragenic recomb
Observed each point mutation affects only one amino acid - each nucleotide is part of 1 codon

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5
Q

Intragenic Recombination

A

Insertions, deletions, gene duplications that lead to sudden changes in structure of genome sequences
Mutations in difference nucleotide pairs can effect the same amino acid - intragenic

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6
Q

Frameshift Mutations

A

Insertions and deletions that do not involve multiples of 3 which distupts the triplet frame reading
Tested by infecting phages with proflavin, caused insertion/deletions
second dose restored wild type

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7
Q

Crick and Brenner Frameshift

A

Used + and - frameshift mutations to determine codons are triplets
Combinations of 3+ and 3- mutations restore frame reading

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8
Q

In Vitro Translation

A

Allows synthesis of simple polypeptides for easy analysis

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9
Q

Polarities in DNA, mRNA and Polypeptide

A

Template DNA comlementary to mRNA
RNA-like strand of DNA has same polarity and sequence as mRNA
5’-3’ in the mRNA corresponds to N-C terminus in polypeptide

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10
Q

Stop Codons and Start Codon

A

Nonsense codons - do not code for amino acids
UAG
UAA
UGA
Start - AUG

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11
Q

3 Ways Mutations can be Created

A

Frameshift
missense - single nucleotide sub
nonsense

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12
Q

Initiation

A

RNA polymer binds to promoter sequence
Sigma factor binds to RNA, region of DNA unwound to form open promoter complex
Phosphodiester bonds between first 2 ribonucleotides

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13
Q

Elongation

A

Constructing RNA copy of gene
σ factor separates from RNA polymerase
Core RNA looses affinity for promoter, moves to 3’-5’ direction on template strand
Within transcription bubble NTPs added to 3’ end

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14
Q

Termination

A

End of transcription in prokaryotes
Terminators are RNA sequences that signal the end
2 kinds in bacteria - extrinsic (require additional factors) and intrinsic (no other factors needed)

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15
Q

Transcription: Eukaryote vs Prokaryote

A

Eukaryotes - enhancers, required for efficient transportation

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16
Q

Transcription: Product

A

Primary transcript - single strand RNA
- Prokaryotes - mRNA
Eukaryotes - 1’ transcript processed to mRNA

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17
Q

mRNA - Eukaryotes

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A

Methylated cap at 5’ end
Capping enzyme adds backwards G to 1st nucleotide of 1’ transcript
Adds tail to 3’ end of mRNA

18
Q

RNA Splicing

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A

Removes Introns (intervening regions) and joins adjacent exons
3 short sequences in 1’ transcript determine where splicing occurs

19
Q

Exons

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A

Expressed regions - sequences found in a genes DNA and mature mRNA

20
Q

Introns

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A

Intervening regions - sequences found in DNA but not mRNA
Some eukaryote genes may have introns

21
Q

Splicing Mechansim

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A

3 short sequences
- splice donor
- branch site
- splice acceptor
2 sequential cuts remove an intron
Catalyzed by spliceosome

22
Q

Alternative Splicing

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A

Produces different mRNAs from the same 1’ transcript

23
Q

Transfer RNA Purpose

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A

Mediate translation of mRNA codons to amino acids
Carry specific amino acids and match with mRNA code for assembly

24
Q

tRNA Structure

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A

1’ - nucleotide sequence
2’ - clover leaf shape
3’ - L shape, 3D folding

25
Aminoacyl-tRNA synthetases function
catalyzes attachmetn of tRNA to specific amino acids recognizes features of corresponding tRNA to connect them
26
tRNA Properties
-short single strand RNAs - 74-95nt -each has anticodon - complementary to mRNA codon -specific tRNA covalently coupled to specific amino acid (Charged tRNA) -base pairing between mRNA codon and anticodon of charged tRNA directs amino acid into polypeptide
27
Wobble
Some tRNA recognize more than 1 codon flexibility in base pairing between 3' nucleotide in codon and 5' nucleotide in anticodon - enables tRNAs to recognize all possible codons
28
Ribosome: Purpose
Site of polypeptide synthesis - composed of proteins and ribosomal RNAs -Coordinate tRNA to match genetic instructions of mRNAs - facilitate translation
29
Ribosome: Structure
2 subunits composed of RNA and protein Different parts have different functions - small subunit binds to mRNA - large subunit has peptidyl transerase - catalyzes new peptide bonds - 3 distinct tRNA binding areas - E, P, A
30
Ribosome: Translation of mRNA
Initiation - prokaryotes - ribosome binds to Shine-Dalgarno box and AUG - eukaryotes - ribosomal subunit binds to methylated 5' cap then migrates to first AUG codon Elongation - addition of amino acids to C-teriminus Termination - release factors recognize and bind to stop codons - release ribosomal subunits, mRNA and polypeptide
31
Gene Expression: Prokaryotes vs Eukaryotes
Prokaryotes - no nucleus - transcription/translation in same place - genes not divided into exons and introns -accessible promoters - initiator tRNA carries formylmethionine - multiple RBSs - synthesize different polypeptides - Small ribosomal subunit immediately binds to mRNA site Eukaryotes - transcription in nucleus, translation in cytoplasm - DNA - exons separated by introns enhancers located far from propter stabilize RNA polymerase at promoter - initiator tRNA carries methionine - small ribsosomal subunit binds to cap at 5' end then scans to find binding site
32
Silent Mutations
Do not alter amino acid sequence degenerate genetic code
33
Misssense Mutations
Replace one amino acid with another - Conservative - chemical properties of mutant amino acid are different from the original - Nonconservative - chemical properties of mutant amino acid are different from the original amino acid
34
Nonsense Mutations
Change codon that encodes amino acid to a stop codon
35
Frameshift Mutation
results from insertion or deletion of nucleotides with the coding region
36
LOF Allele: Null (Amorphic) Mutations
Completely block function of a gene product ex- deletion of an entire gene
37
LOF Allele: Hypomorphic Mutations
Produce less of a wild type protein, or less effective protein
38
Loss of Function Alleles
- Can show incomplete dominance - phenotype varies with amount of functional gene - Can be dominant to wild type
39
LOF Allele: Haploinsufficiency
One wild type allele does not produce enough gene product to avoid mutant phenotype
40
GOF: Hypermorphic
Generate more gene product or same amount of more efficient gene - Achondroplasia
41
GOF: Neomorphic Mutations
Generate gene product with new function or that is expressed at an inappropriate time or place - Ectopic expression- - dominant
42
GOF: Antimorphic (Dominant Negative)
Prevent normal protein from function - dominant or incompletely dominant

Genetics Final Exam (11 decks)

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