Section 1
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Last updated
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Date created
Mar 1, 2020
Cards (55)
Section 1
(50 cards)
Domains
functional regions part of protein architecture
Alternative RNA Splicing
many genes can give rise to 2+ polypeptides, depending on which segments are treated as exons during RNA processing -# different protein products > # genes
Exons
nucleotide regions that are expressed, usually translated into amino acid sequences
Signal Recognition Particle (SRP)
brings ribosome to receptor protein into ER membrane
Insertions
additions of nucleotide pairs in gene
Deletion
losses of nucleotide pairs in gene
Nonsense Mutation
-change codon for amino acid into stop codon -causes translation to be terminated prematurely -resulting polypeptide shorter than polypeptide encoded by normal gene
Mutagen
physical and chemical agents that interact w/ DNA that cause mutations
Codons
mRNA base triplets written 5'-3' direction
Ribozymes
RNA molecules that function as enzymes, can b/c: 1. RNA single stranded, region of RNA molecule may base-pair w/ complementary region elsewhere in same molecule-gives molecule particular 3D structure-essential to catalytic function of ribozymes, just like in enzymatic proteins 2. some RNA bases have functional groups that may participate in catalysis 3. ability of RNA to hydrogen bond w/ other nucleic acid molecules-adds specificity to catalytic activity
Translation
-synthesis of polypeptide -occurs under direction of mRNA -change in language-cell must translate base sequence of mRnA molecule into amino acid sequence of polypeptide -occurs in cytoplasm
Missense Mutations
-change one amino acid to another -new amino acid may have properties similar to replaced amino acid, or may be in region where exact sequence of amino acids not essential to proteins functions
A Site (aminoacyl-tRNA site)
holds tRNA carrying next AA to be added in chain
Ribosomal RNA (rRNA)
made in nucleolus, make up ribosomal subunits
Wobble
flexible base pairing at codon position
P Site (peptidyl-tRNA site)
holds tRNA carrying growing polypeptide chain
Spliceosome
interacts w/ certain sites along introns, releasing intron and joining together 2 exons that flanked intron
RNA Polymerase
-pries 2 strands of DNA apart -joins RNA nucleotides as they base pair along DNA template -assemble polynucleotides 5' -> 3' -can start chain from scratch-no primer needed
Triplet Code
genetic instructions for polypeptide chain written in DNA as series of non-overlapping, 3 nucleotide words
Mutations
-change into genetic information of cell -responsible for huge diversity of genes found along organisms
Signal Mechanism for Targeting Proteins to ER
1. polypeptide synthesis begins on free ribosome in cytosol 2. SRP binds to signal peptide, halting synthesis momentarily 3. SRP binds to receptor proteins in ER membrane (receptor is part of protein complex w/ membrane and signal cleaving enzyme) 4. SRP leaves, and polypeptide synthesis resumes w/ simultaneous translocation across membrane (signal peptide stays attached to translocation complex) 5. signal cleaving enzyme cuts off signal peptide 6. rest of complexed polypeptide leaves ribosome and folds into final conformation
Transcription
-synthesis of RNA under direction of DNA -DNA serves as template for assembling complementary RNA molecule -resulting RNA molecule faithful transcript of gene's protein-building instructions -occurs in nucleus
Transcription Factors
proteins that mediate binding of RNA polymerase and initiation of transcription
Release Factor
protein that binds to stop codon @ A site
Base Pair Substitutions
replacement of one nucleotide and its partner w/ another pair of nucleotides
Introns
noncoding segments of nucleic acid that lie between coding regions
Frameshift Mutations
-# nucleotides inserted/deleted NOT multiple of 3 -may alter reading frame of genetic message
Primary Transcript
initial RNA transcript from any gene, including those coding for RNA that is not translated into protein
rRNA
makes up 60% of the ribosome; site of protein synthesis
Anticodon
nucleotide triplet that base pairs of complementary codon of mRNA
Terminator
sequence that signals end of transcription in bacteria
TATA Box
crucial promoter DNA sequence
Transcription Unit
stretch of DNA transcribed into RNA molecule
RNA splicing
removal of large portions of RNA molecule initially synthesized
Transfer RNA (tRNA)
transfer amino acids from cytoplasmic pool of AA to ribosome
Aminoacyl tRNA Synthetases
-able to bind to different tRNAs that code for specific amino acid -catalyzes covalent attachment to tRNA -> aminoacyl tRNA released from enzyme -available to deliver AA to growing polypeptide chain of ribosome
E Site (exit site)
where discharged tRNAs leave ribosome
Template Strand
DNA strand that provides pattern/template for sequence of nucleotides in RNA transcript
poly-A Tail
-50-250 more A nucleotides added to 3' end by enzyme 1. facilitates export of mature mRNA from nucleus 2. helps protect mRNA from degradation by hydrolytic enzymes 3. helps ribosomes attach to 5' end of mRNA once mRNA reaches cytoplasm
RNA Processing
enzymes in eukaryotic nucleus modify pre-mRNA in specific ways before genetic messages dispatched to cytoplasm
Promoter
DNA sequence where RNA polymerase attaches and initiates transcription
5' Cap
modified form of guanine added onto 5' end after transcription 1. facilitates export of mature mRNA from nucleus 2. helps protect mRNA from degradation by hydrolytic enzymes 3. helps ribosomes attach to 5' end of mRNA once mRNA reaches cytoplasm
Polyribosomes
-strings of ribosomes trailing along mRNA -enables cells to make many copies of polypeptide quickly
Point Mutations
-chemical changes in a single base pair of a gene -if occurs in a gamete, can be transmitted to offspring and future generations
Gene Expression
process by which DNA directs synthesis of proteins
Signal Peptide
-targets protein to ER -marks if polypeptide of proteins destined for endomembrane system or for secretion
Reading Frame
grapings w/ symbols w/ message that needs to be translated to written language
Transcription Initiation Complex
complex of transcription factors and RNA polymerase II bound to promoter
Messenger RNA (mRNA)
RNA molecule that carries genetic message from DNA to protein synthesizing machinery of cell
Ribosomes
-sites of translation -complex particles that facilitate orderly linking of amino acids into polypeptide chains
Section 2
(5 cards)