Molecular Genetics

Protein SynthesisGene RegulationMutationsBiotechnology

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

Chromosomal Mutations

Deletions

Duplications

Inversions

Translocations