DNA/RNA.Lecture

I. How does DNA affect phenotype?

A. Archibald Garrod (1909)

B. George Beadle & Edward Tatum (early 1940’s)

C. Overview: information flow & gene expression

II. Transcription

A. Structure

1. nucleotide differences

2. RNA

3. short

B. When does this happen?

C. 3 main kinds of RNA

1. messenger RNAs (mRNA)

2. Other 2 types of RNA - protein-producing machinery

a. transfer RNAs (tRNA)

b. ribosomal RNAs (rRNA)

D. How is it made?

1. Musical analogy

2. similar

a. DNA

b. the information

c. RNA

3. RNA polymerase

a. 3’ end

b. promoter

termination signal

c. transcription unit

d. synthetic process

4. Steps:

a. initiation

1) initiator site

2) upstream

3) RNA polymerase

b. elongation

c. termination & release

d. 1 chromosome can have

E. major differences between prokaryotes & eukaryotes

1. in prokaryotes

2. in eukaryotes

promotor structure in more detail [17.8]

influencing initiation

TATA box

UPE

enhancers

activators

2) transcription factors

c. termination & release of RNA transcript

termination sites

d. post-transcriptional modifications

1) capping

2) tailing

3) removal

(i) involve

- small nuclear RNAs (snRNAs)

small nuclear riboproteins (snRNPs)

- spliceosomes

ribozymes

(ii) alternative splicing

III. Translation

A. foreign language analogy

B. what is it saying?

1. codons

redundancy or degeneracy

Marshall Nirenberg & JH Matthaei

Nobel Prize 1968: Nirenberg, Khorana & Holley

Story about that time:

C. How is a protein built?

1. Takes ribosomes

a. made of large & small subunits

b. have 3 sites for tRNAs

c. catalytic activities

(ribosome structure:

2. Takes tRNAs

a. aminoacyl-tRNA synthetases

b. tRNA structure

anticodon loop

wobble

3. mRNA

4. GTP

D. Steps:

1. initiation

initiation complex

2. chain elongation

a. codon recognition

b. peptide bond formation

c. translocation

d. repeat

3. chain termination

stop codon

release factor

E. polyribosomes/polysomes

F. proteins are folding into their final shape

G. post-translational modifications

1. modified

2. signal sequences of protein

a. proteins for the RER

1) signal peptide/sequence

2) signal-recognition particle (SRP)

3. further editing can also occur: eg: insulin

IV. How accurate do all these processes have to be?

A. mutation

B. point mutation

1. base-pair substitution

a. silent

b. missense

c. nonsense

2. frameshift mutation

a. base-pair insertion

b. base-pair deletion

C. larger DNA changes

1. chromosomal

2. transposon

3. viruses

D. is mutation always bad?

1. bad

2. not so bad

3. good

E. How to test chemicals for mutation-causing ability

1. for mutagens

2. for carcinogens

Helpful resources:

DNA from the Beginning- Molecules of Genetics:

The Biology Project: Molecular Biology

http://www.biology.arizona.edu/molecular_bio/molecular_bio.html

NDSU Virtual Cell: Transcription

Biology / Medicine Animations HD: Transcription

NDSU Virtual Cell: Translation

DNA Learning Center – 3D Animation Library