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Genetics Final Exam > Chapter 9 > Flashcards

Chapter 9 Flashcards

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Biology 101 flashcards
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

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

A

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

19
Q

Exons

A

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

20
Q

Introns

A

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

21
Q

Splicing Mechansim

A

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

22
Q

Alternative Splicing

A

Produces different mRNAs from the same 1’ transcript

23
Q

Transfer RNA Purpose

A

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

24
Q

tRNA Structure

A

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

25
Q

Aminoacyl-tRNA synthetases function

A

catalyzes attachmetn of tRNA to specific amino acids
recognizes features of corresponding tRNA to connect them

26
Q

tRNA Properties

A

-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
Q

Wobble

A

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
Q

Ribosome: Purpose

A

Site of polypeptide synthesis
- composed of proteins and ribosomal RNAs
-Coordinate tRNA to match genetic instructions of mRNAs
- facilitate translation

29
Q

Ribosome: Structure

A

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
Q

Ribosome: Translation of mRNA

A

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
Q

Gene Expression: Prokaryotes vs Eukaryotes

A

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
Q

Silent Mutations

A

Do not alter amino acid sequence
degenerate genetic code

33
Q

Misssense Mutations

A

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
Q

Nonsense Mutations

A

Change codon that encodes amino acid to a stop codon

35
Q

Frameshift Mutation

A

results from insertion or deletion of nucleotides with the coding region

36
Q

LOF Allele: Null (Amorphic) Mutations

A

Completely block function of a gene product
ex- deletion of an entire gene

37
Q

LOF Allele: Hypomorphic Mutations

A

Produce less of a wild type protein, or less effective protein

38
Q

Loss of Function Alleles

A
  • Can show incomplete dominance - phenotype varies with amount of functional gene
  • Can be dominant to wild type
39
Q

LOF Allele: Haploinsufficiency

A

One wild type allele does not produce enough gene product to avoid mutant phenotype

40
Q

GOF: Hypermorphic

A

Generate more gene product or same amount of more efficient gene
- Achondroplasia

41
Q

GOF: Neomorphic Mutations

A

Generate gene product with new function or that is expressed at an inappropriate time or place - Ectopic expression-
- dominant

42
Q

GOF: Antimorphic (Dominant Negative)

A

Prevent normal protein from function
- dominant or incompletely dominant

Genetics Final Exam (11 decks)

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