RNA and Protein Synthesis

Ribonucleic acid: another type of nucleic acid that works with DNA

to make proteins

mRNA

From nucleus to cytoplasm

DNA

transcription

nucleus cytoplasm

translation

trait

aa

aa

aa

aa

aa

aa

aa

aaaa

aa

protein

DNA vs. RNADNA deoxyribose sugar nitrogen bases

G, C, A, TT : AC : G

double stranded 1 type

RNA ribose sugar nitrogen bases

G, C, A, UU : AC : G

single stranded 3 types: M, R, & T

Transcription Making mRNA from DNA DNA strand is the

template (pattern)match bases

U : A G : C

EnzymeRNA polymerase

Matching bases of DNA & RNA Double stranded DNA unzips

A G GGGGGT T A C A C T T T T TC C C CA A

Matching bases of DNA & RNA Double stranded DNA unzips

A G GGGGGT T A C A C T T T T TC C C CA A

Matching bases of DNA & RNA Match RNA bases to DNA

bases on one of the DNA strands

U

A G GGGGGT T A C A C T T T T TC C C CA A

U

UU

U

U

G

G

A

A

A C CRNA polymerase

C

C

C

C

C

G

G

G

G

A

A

A

AA

Matching bases of DNA & RNA U instead of T is matched to A

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNAaa

aa

aa

aa

aa

aa

aa

aaaa

aa

U C CCCCCA A U G U G A A A A AG G G GU Uribosome

aa

aa

aa

aa

aa

aa

aa

aaaa

aa

protein

cytoplasm

nucleus

traitU C CCCCCA A U G U G A A A A AG G G GU U

ribosome

How does mRNA code for proteins mRNA leaves nucleus mRNA goes to ribosomes in cytoplasm Proteins built from instructions on mRNA

aa aa aa aa aa aa aa aa

How?

mRNA

U C CCCCCA A U G U G A A A A AG G G GU U

How does mRNA code for proteins?

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA

Met Arg Val Asn Ala Cys Alaprotein

?

How can you code for 20 amino acids withonly 4 DNA bases (A,U,G,C)?

ribosome

aa aa aa aa aa aa aa aa

AUGCGUGUAAAUGCAUGCGCCmRNA

mRNA codes for proteins in triplets

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA

Met Arg Val Asn Ala Cys Alaprotein

?

Codon = block of 3 mRNA bases

codon

ribosome

For ALL life!strongest support

for a common origin for all life

Code has duplicatesseveral codons for

each amino acidmutation insurance!

Start codonAUGmethionine

Stop codonsUGA, UAA, UAG

The mRNA code

How are the codons matched to amino acids?

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA

anti-codon

codon

tRNAUAC

MetGCA

ArgCAU

Val Anti-codon = block of 3 tRNA bases

aminoacid

mRNA to protein = Translation The working instructions mRNA The reader ribosome The transporter transfer RNA (tRNA)

mRNAU C CCCCCA A U G U G A A A A AG G G GU U

aaaa

aa

tRNA

GGU

aa

tRNA

U A C

aa

tRNA

GA C

tRNA

aa

A GU

ribosome

aa

aa

aaaa

aa

aa

aa

mRNA

From gene to protein

DNA

transcription

nucleus cytoplasm

protein

translation

trait

U C CCCCCA A U G U G A A A A AG G G GU Uribosome

tRNA

aa

MutationsChanges to DNA are called mutations

change the DNAchanges the mRNAmay change proteinmay change trait

DNA TACGCACATTTACGTACG

mRNA AUGCGUGUAAAUGCAUGC

aa aa aa aa aa aa aaprotein

trait

Types of Mutations

1.Point mutation: change in a single base pair in DNA (substitution) THE DOG BIT THE CAT THE DOG BIT THE CAR

Missense mutation = changes amino acidNonsense mutation = change to STOPSilent mutation = no change in protein

Types of Mutations

2. Frameshift mutation: a single base pair is added or deleted and shifts the reading of the codons

THE DOG BIT THE CAT

THE DOG SBI TTH ECA T

Mutations

3. Chromosomal mutations: any change in the structure or number of chromosomes, common in plants deletion: part of a chromosome is removed insertion and translocation: part of a

chromosome breaks off and attaches to another chromosome

inversion: part of a chromosome breaks off and is reinserted backwards

Examples of chromosomal mutations

deletion

duplication

inversion

translocation

12.4

Gene Regulation

Only a small percent of genes are expressed (~3%)

Genes that are expressed have a proteins that control their expression

“TATA box”: sequence at the beginning of a transcription site in eukaryotes

The Operon

Four regions of DNA control the production of a protein

a structural gene that holds the codons for the amino acid sequence found in the enzyme.

an operator region right in front of the structural gene.

a promotor region where the RNA polymerase will bind to the DNA.

a regulator gene which has a role in controling the transcription from the structural gene.

The combined region of the operator and structural gene is called an operon.

Animations

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter15/animations.html#

http://learn.genetics.utah.edu/units/basics/firefly/