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78 Cards in this Set

  • Front
  • Back
Archibald Garrod
One gene - one enzyme
Alkaptonuria - enzyme metabolism of alkaptans
Beadle and Tatum
Proved One gene - one enzyme hypothesis -Bread Mold mutations
Central Dogma
DNA -> RNA -> Protein
Transcription
Translation
Transcription
RNA synthesis under the direction of DNA in nucleus
Translation
(Eukaryote)
Polypeptide synthesis under the direction of mRNA at the ribosome(s) in the cytoplasm
Gene
programs protein synthesis via genetic messages in the form of messenger RNA
Exon
Expressed nucleic acid sequences
Intron
Intervening nucleic acid sequences
Codon
Triplets of nucleotides that represent a single amino acid
Mutagen
Physical and chemical agents that cause DNA mutation
RNA processing
modification of preMessenger RNA before genetic messages are passed to the cytoplasm
Anti-codon
nucleotide triplet on tRNA which base pairs with complementary codon on mRNA
Promotor
The DNA sequence where RNA polymerase attaches and initiates transcription
Transcription Factors
a collection of proteins that mediate the binding of RNA polymerase and initation of transcription
Primary Transcript
Initial RNA transcript for any gene (includes expressed and intervening sequences)
Three stages of Transcription
1. Initiation
2. Elongation
3. Termination
Metabolic Pathway
Cells synthesize and degrade most organic chemicals by sequences of reactions that are catalyzed by enzymes
One gene - One Polypeptide
Restatement of one gene one enzyme or one gene one protein
Alkaptonuria
A rare genetic inability to make the enzyme that metabolizes Alkapton
messenger RNA (mRNA)
carries genetic message specifying amino acid sequences from the DNA in the nucleus to the protein–synthesizing machinery (ribosomes) in the cytoplasm
Ribosome
Eukaryote Translation
coordinate the sequential coupling of tRNA molecules to mRNA codons
Start codon
where translation initiates
AUG
Stop codon
where translation terminates
UAA UAG UGA
transfer RNA (tRNA)
cloverleaf-shaped structure which carries the appropriate amino acid to the ribosome
Two methods of post-transcriptional modification
1. Alternation of mRNA ends
2. Splicing
Template strand
Strand of DNA that provides the template for ordering the sequence of nucleotides in an RNA transcript
NOTE: only one of the two DNA strands is transcribed.
5' Cap
a modified guanine nucleotide is added to the 5’ end of the transcript
3' Poly-A Tail
50-250 adenine nucleotides are added to the 3’ end of the transcript by poly-a polymerase (enzyme)
Purpose of end modification
1.Help export mature mRNA out of nucleus
2. Protect mRNA from degradation by hydrolytic enzymes
3. Help ribosomes attach to the mRNA
Why Splicing?
removes intervening sequences (introns) from the mRNA transcript
Why splicing ? 2
1. One gene can encode more than one polypeptide
2. Gets rid of evolutionary “junk DNA”
Exon Shuffling (1)
giving more room for crossover events between exons may increase chances for formation of beneficial new proteins,
NOTE: sexual traits in flies
Reading frame
The way a cell′s mRNA–translating machinery groups the mRNA nucleotides into codons
Triplet code
A set of three–nucleotide–long words that specify the amino acids for polypeptide chains.
transcription initiation complex
The completed assembly of transcription factors and RNA polymerase bound to the promoter.
TATA box
A promoter DNA sequence crucial in forming the transcription initiation complex.
a nucleotide sequence contain "TATA" about 25 nucleotides upstream from transcription start point
RNA polymerase II
used for mRNA synthesis in eukaryotes.
sliceosome
A complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons.
Ribozyme
An enzyme–like RNA molecule that catalyzes reactions during RNA splicing
domains
1. discrete structural and functional regions of a protein
2. correspondence to exons splicing
Exon shuffling (2)
allows for creation of proteins with multiple polypeptides and multiple structural and functional domains
aminoacyl–tRNA synthetase
An enzyme that joins each amino acid to the correct tRNA
aminoacyl–tRNA
An "activated amino acid"
wobble
A relaxation of the base–pairing rules so
third nucleotide of a tRNA anticodon can form hydrogen bonds with more than one kind of base
Ribosomal RNA (rRNA)
Plays catalytic (ribozymes) and structural roles in the ribosome.
Created in nucleolus
P-Site
holds the tRNA carrying the growing polypeptide chain
NOTE: peptidyl–tRNA site
A-Site
holds the tRNA carrying the next amino acid to be added to the chain
NOTE:aminoacyl–tRNA site
E-Site
place where discharged tRNAs leave the ribosome.
NOTE: EXIT site
Three stages of Transcription
1. Initiation
2. Elongation
3. Termination
Transcription Initiation
1. RNA Polymerase binds to the promoter
2. DNA strands unwind
3. RNA synthesis initiates at the start point of template strand
Transcription Elongation
1. RNA polymerase:
a.continues to untwist the double helix,
b. adds nucleotides to the 3′ end of the growing RNA molecule
2. the new RNA molecule peels away from its DNA template
3. DNA double helix re–forms
Transcription Termination
(Eukaryote)
the polymerase transcribes a sequence on the DNA called the polyadenylation signal sequence, which codes for a polyadenylation signal (AAUAAA) in the pre–mRNA
Three stages of Translation
1. Initiation
2. Elongation
3. Termination
Translation Initiation
1.small ribosomal subunit binds to both mRNA and a specific initiator tRNA
2.The small subunit then scans, downstream for the start codon
Translation Elongation
1. Codon Recognition
2. Peptide Bond formation
3. Translocation
Translation Termination
stop codon in the mRNA reaches the A site of the ribosome
Polysome
An aggregation of several ribosomes attached to one messenger RNA molecule
NOTE: Polyribosome
post–translational modifications
may be required before the protein can provide a specific function in the cell
Bound ribosomes
make proteins of the endomembrane system (the nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane) as well as proteins secreted from the cell
Free ribosomes
suspended in the cytosol and mostly synthesize proteins that dissolve in the cytosol and function there
signal peptide
A stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell
signal–recognition particle (SRP)
A protein–RNA complex that recognizes a signal peptide as it emerges from the ribosome
translocation complex
protein complex that has membrane pore and signal-cleaving enzyme
RNA is multifunctional - Why?
RNA:
1. Can hydrogen–bond to other nucleic acid molecules.
2. can assume a specific conformation by forming hydrogen bonds between bases in different parts of its own polynucleotide chain.
3. has functional groups that allow it to act as a catalyst (ribozyme).
Small nuclear RNA (snRNA)
SNURPs
structural and catalytic roles in sliceosomes
SRP RNA
component of signal recognition particle (SRP)
Small nucleolar RNA (snoRNA)
aids in processing of pre-RNA transcripts for ribosome subunit formation in the nucleolus
small interfering RNA (siRNA) and microRNA (miRNA)
involved in regulation of gene expression
Mutation
A change in the DNA of a gene, ultimately creating genetic diversity
Point Mutation
A change in a gene at a single nucleotide pair
Genetic disease or disorder
a mutation that has an adverse effect on the phenotype of an organism
base-pair substitution
the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides
base-pair substitution of third codon
No effect to organisms Phenotype - rules are relaxed - wobble
Missense mutation
a base–pair substitution in which the new codon still codes for an amino acid
Nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein
Insertion mutation
A mutation involving the addition of one or more nucleotide pairs to a gene
Deletion mutation
A mutation involving the deletion of one or more nucleotide pairs to a gene
Frameshift mutation
number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the following nucleotides into codons