Ch 7: Microbial Genetics

Nucleotide (2.27)

(2.25)

(2.26)

antiparallel

Base-pairs

Theory

Idea

Prokaryotic chromosome(s)

Eukaryotic chromosomes - condensation

gene or group of genes

Bacterial chromosome map

DNA replication

DNA replication

3’

DNA replication

5’

Replication of a prokaryotic chromosome

Replication of a eukaryotic chromosome

Where the energy comes from

genotype

phenotype

Serratia at 25 & 37 oC

Transcription

3 kinds of RNA

5’3’

5’3’

3’

3’5’

5’

5’

terminator

Eukaryotic transcription

mRNA modification

Cap

Tail

Edit

Translation: Universal Genetic Code

41

42

43

5’3’

ribosomes

large

large

small

small

Flattened (2D) view

more 3D view

Where amino acid binds

Where it binds to mRNA

tRNAs

Translation: initiation

Peptidyl Amino-acyl

exit

Translation: elongation

Translation: termination

Translation differences

Control of gene expression

Prokaryotic genes

lac operon: makes enzymes for lactose catabolism

inducible

more usual

more unusual

trp operon: makes enzymes for tryptophan synthesis

repressible

more usual

more unusual

Mutations: point

5’ 3’

Nitrous acid

Mutagens

Mutagens

Non-ionizing radiation

4 kinds of DNA repair

Positive selection

rare

see more

replica plating

Negative selection

Ames Test for mutagens

(or a little)

Vertical transfer = between generations {from parent(s) to offspring}

Horizontal transfer = between contemporaries (sometimes different species)

Usual genetic recombination mechanisms in eukaryotes

sex

crossing-over during meiosis

Transformation: DNA from the environment

Transduction

Bacterial conjugation

Producing an Hfr cell

Transposons

aka. “jumping genes”

McClintock (NP 1983)

Ultimate source of Human Genetic information:

Online Mendelian Inheritance in Man (OMIM)

(at the National Library of medicine website)

http://www.ncbi.nlm.nih.gov/