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chapter 17 - Coggle Diagram
chapter 17
translation
ribosomes coordinate the three stages of translation initiation, elongation, and termination. formationof peptide binds between amino acids is catalyzed by RNA's as tRNA's move through the A and P sites and exit through the E site.
after translation durinf protein processing proteins may be modified by cleavage or by attachment of sugars , lipids, phosphates, or other chemical groups
a ribosome made up of ribosomal RNA's and proteins facilitate coupling with binding sites for mRNA and tRNA.
free ribosomes in the cytosol initiate synthesis of all proteins but proteins with a signal peptide are synthesized on the ER
a cell trasnlates an mRNA message into a protein using tRNA's. after being bound toa specific amino acid by an aminoacyl-tRNA synthetase a tRNA lines up via its anticodon at the complimentary codon on mRNA.
a gene can be transcribed by multiple RNA polyemerases simultaneously. a single mRNA molecule can be translated simultaneously by multiple by a number of ribosomes forming a polyribosome.
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Genes
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during gene expression information encoded in genes is used to make specific polypeptide chains or RNA molecules
Gene expression- Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product.
Beadle and Tatums studies of mutant strains of neurospora led to the one gene one polypeptide hypothesis
transcription
a promoter often including a TATA box in eukaryotes establishes where RNA is initiated. transcription factors help eukaryotic RNA polyemerase recognize promoter sequences forming a transcription initiation complex.. termination differs in bacteria and eukaryotes
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three stages of transcription are initiation, elongation, and termination.
RNA synthesis is catalyzed by RNA polymerase which limks together RNA nucleotides complimentary to a DNA template strand. uracil substitutes for thyamine in RNA
RNA modification
most eukaryotic genes are split into segments. they have interspersed among the exons. in RNA splicing introns are removed and exons joined. RNA splicing typically carried out by spliceosomes but in some cases catalyzes its own splicing.
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eukaryotic mRNA's undergo RNA processing which includes RNA splicing the addition of a modified 5' cap to yhe 5' end and the addition of a poly- A tail to the 3' end.
mutations
small scale mutations include a point mutations changes one DNA nucleotide pair which may lead to production of non functional proteins. nucleotide pair substitutions can cause missense or nonsense mutations nucleotide pair insertions or deletions may produce frame shift mutations
apontaneous mutations can occur during DNA replication and recombination. chemical and physical mutagens cause DNA damage that can alter genes