Molecular Genetics Protein Synthesis Gene Regulation Mutations Biotechnology

Protein Synthesis TranscriptionTranslation DNA  RNA  Proteins In nucleuson Ribosomes

RNA RNA is ribonucleic acid. Like DNA:  Made up of nucleotides  Codes 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 RNA Messenger 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

Transcription RNA 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 RNA  A – U (instead of T)  C - G

Translation The Genetic Code The “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 transcribed  2 – 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 Regulation Prokaryotes  Operon- a group of genes that operate together lac operon contains an operator region that can determine whether the gene is expressed or not When the repressor is attached to the operator and the gene is not expressed When lactose is present the repressor releases and the genes are expressed Eukaryotes  TATA box- helps position RNA polymerase for transcription  Highly complex

12-4 Mutations Gene mutations:  Point mutations – involve changes in one or a few nucleotides Substitutions  Frameshift mutations – shift the “reading frame” of the genetic message Insertions Deletions Ex: AUG UGG CCU UAC → AUG UGG ACC UUA C

Point Mutations DNA: TAC G C A TGG AAT mRNA: AUG CGU ACC UUA Amino Acids: Met-Arg-Thr-Leu SUBSTITUTION DNA: TAC G T A TGG AAT mRNA: AUG CAU ACC UUA Amino Acids: Met-His-Thr-Leu DNA: TAC GCA TGG AAT mRNA: AUG CGU ACC UUA Amino Acids: Met-Arg-Thr-Leu INSERTION DNA: TA T CGC ATG GAA T mRNA: AUA GCG UAC CUU A Amino Acids: Ile-Ala-Tyr-Leu

Chromosomal Mutations Deletions Duplications Inversions Translocations