Transcript Molecular Genetics - Lake Travis Independent School District

Molecular Genetics
Protein Synthesis
Gene Regulation
Mutations
Biotechnology
Protein Synthesis
Transcription
Translation
DNA----------- RNA--------- Proteins
In nucleus
on 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 GCA TGG AAT
mRNA: AUG CGU ACC UUA
DNA: TAC GCA TGG AAT
mRNA: AUG CGU ACC UUA
Amino Acids: Met-Arg-Thr-Leu
Amino Acids: Met-Arg-Thr-Leu
SUBSTITUTION
INSERTION
DNA: TAC GTA TGG AAT
mRNA: AUG CAU ACC UUA
DNA: TAT CGC ATG GAA T
mRNA: AUA GCG UAC CUU A
Amino Acids: Met-His-Thr-Leu
Amino Acids: Ile-Ala-Tyr-Leu
Chromosomal Mutations
 Deletions
 Duplications
 Inversions
Translocations