molecular genetics protein synthesis gene regulation mutations biotechnology
TRANSCRIPT
Protein Synthesis
Transcription Translation
DNA----------- RNA--------- ProteinsIn nucleus on Ribosomes
RNARNA is ribonucleic acid.Like DNA:
Made up of nucleotidesCodes for proteins
Unlike DNA:Nucleotides are made of ribose (instead
of deoxyribose)RNA is single-stranded (DNA is
double)The base Thymine is replaced with
Uracil in RNA
3 Types of RNAMessenger RNA (mRNA)
RNA that carries copies of DNA instructions
Ribosomal RNA (rRNA)Make up ribosomes (along with proteins)
Transfer RNA (tRNA)Transfers or carries each amino acid to
the ribosomes as coded for by the mRNA
TranscriptionRNA molecules are produced by
copying part of the nucleotide sequence of DNA into a complementary sequence of RNA
DNA strands are separated, RNA polymerase uses one strand of DNA as a template and assembles RNA
Uses base pairing to assemble RNAA – U (instead of T)C - G
TranslationThe Genetic CodeThe “language” of mRNA is
sometimes called the genetic code.
The genetic code is read 3 letters (or bases) at a time, called codons.
A codon is made up of 3 nucleotides that specify for a single amino acid
Amino acids are strung together to form proteins (polypeptides)
Genetic Code, cont.Ex:
UCGCACGGU
Would be read 3 bases at a time…
UCG-CAC-GGU
Using the code →Serine-Histadine-Glycine
Start and Stop Codons
AUG codon codes for the assembly of amino acids to begin. It also codes for methionine
Three codons code for the assembly of amino acids to stop – UAA, UAG, and UGA
Protein Synthesis (Translation)
Proteins are assembled on ribosomes using information from mRNA
Steps:1 – mRNA transcribed2 – mRNA attaches to ribosome. tRNA matches
anticodons to codons and brings in amino acids.3 – amino acids are joined together by peptide
bonds. Free tRNA molecules float away.4 – polypeptide chain grows until stop codon.
Gene RegulationProkaryotes
Operon- a group of genes that operate togetherlac operon contains an operator region that can
determine whether the gene is expressed or notWhen the repressor is attached to the operator
and the gene is not expressedWhen lactose is present the repressor releases
and the genes are expressed
EukaryotesTATA box- helps position RNA polymerase
for transcriptionHighly complex
12-4 Mutations
Gene mutations:Point mutations – involve changes in one
or a few nucleotidesSubstitutions
Frameshift mutations – shift the “reading frame” of the genetic messageInsertionsDeletionsEx:AUG UGG CCU UAC → AUG UGG ACC UUA C
Point Mutations
DNA: TAC GCA TGG AATmRNA: AUG CGU ACC UUA
Amino Acids: Met-Arg-Thr-Leu
SUBSTITUTION
DNA: TAC GTA TGG AATmRNA: AUG CAU ACC UUA
Amino Acids: Met-His-Thr-Leu
DNA: TAC GCA TGG AATmRNA: AUG CGU ACC UUA
Amino Acids: Met-Arg-Thr-Leu
INSERTION
DNA: TAT CGC ATG GAA TmRNA: AUA GCG UAC CUU A
Amino Acids: Ile-Ala-Tyr-Leu