Microbiology- Protein synthesis

protein synthesis

• DNA redundant

• DNA antiparallel

• DNA semiconservative

DNA 3 pair - triplet

RNA 3 pair- codon

template strand

RNA makes RNA copy

• during elongation

Transcription

• produces an mRNA complementary to the DNA gene

translation

• RNAs use their anticodon to interpret the mRNA codons and bring in the amino acids

school starts in AUGust

Eukaryotic transcription and translation

• don’t occur simultaneously- transcription nucleus and translation cytoplasm

• eukaryotic start codon AUG, does not use formyl methionine

• Eukaryotic mRNA encodes single protein, bacterial mRNA encodes many

• Eukaryotic DNA contains introns- intervening sequences of noncoding DNA- which have to be spliced out of the final mRNA transcript. spliceosomes

Introns and exons- DOESNT OCCUR IN PROKARYOTES

• alternative SPLICING

• exons and introns dynamic

Prokaryotes

polyribosomal complex- 1 mRNA strand read by multiple ribosomes; lots of copies

• tRNA has anticodon and CCA amino acid binding end

• Translation bacteria formation of initiation complex. 50s subunit binds

• transcription and translation simultaneously in cytoplasm. Rapid cellular response

• Nucleus: DNA template, primary mRNA trabscript, transcript processed by special enzymes, spliceosomes released

• Cytoplasm: mRNA transcropt can now be translated

Operons

2 types

• inducible- operon turned ON by substrate; catabolic operons- enzymes needed

• Repressible- genes in a series are turned off by product synthesized

Lactose Operon: Inducible Operon

• Made up of 3 segments

• regulator- gene that codes for repressor

• control locus- composed of promoter and operator

• structural locus: made of 3 genes each coding for an enzyme needed to catabolize lactose

  • B galactosidase- hydrolyzes lactose

  • permease- brings lactose across cell membrane

  • B-galactosidase transacetylase- uncertain function

Lac operon

• off

  • absence of lactose, repressor binds with operator locus and blocks transcription of downstream structural genes

• lactose turns the operon on by acting as the inducer

  • binding of lactose to the repressor protein changes its shape and causes it to fall off of operator. RNA polymerase bind to promoter.

Arginine Operon: Repressible

• arginine amino acid needed for proteins

• normally on and will be turned off when the product on the pathway is no longer required

• when excess arginine is present, binds to repressor and changes it. repressor binds to operon . corepressor

Mutations

• mutation: changes in phenotype due to change in genotype (nitrogen base sequence of DNA)

• wild type: natural nonmutated characteristics

• mutant strain: organism has mutation

Spontaneous mutations

• random changes in DNA due to errors in replication that occurs without known cause

Induced- exposed to mutagens,

• point mutation: addition, deletion, or substitution of a single base

• missense mutation: causes change in a single amino acid

• nonsense mutation: changes in a normal codon into stop codon

• silent mutation: alters a base but does not change the amino acid

• back mutation: when mutated gene reverses to its original base composition

• frameshift mutation: when the reading frame of the mRNA is altered

  • insertion

  • deletion

more damaging: single base out? add single base in? remove three?

• remove one or add one FATAL ERROR

Repair of Mutations

• DNA polymerase: proofreads nucleotides during DNA replication

• mismatch repair: locates and repairs mismatched nitrogen bases that were not repaired by DNA polymerase

• light repair

• excision repair

Ames test- chemical capable of mutating bacterial dna can mutate mammalian DNA

• is this thing carcinogenic?

• if cause mutations? assume carcinogenic

• ag, industrial, medicinal compounds screened

• Salmonella typhimurium lost ability to synthesize histidine

• control plate (no growth/contaminant/mutant) and experimental plate (expose to chemical then add to bacteria) colonies on test vs colonies on control: how mutagenic

Positive and Negative Effects of Mutations

• leading to nonfunctional proteins are harmful, possibly fatal

• mutations beneficial to environment cant readily adapt, survive, and reproduce - are basis of change in pop

Conjugation

Conjugation

• transfer of a plasmid or chromosomal

• fertility plasmid

transformation

• capsule gene

General Transduction

• dna in

How are patterns of gene flow different in viruses? What are retroviruses? Why are they important in genetic engineering?

What is a polymerase chain reaction? What special enzyme is utilized in this

procedure? What are the products? How can these products be of use?

What is the relationship between reverse transcriptase and cDNA? What are the advantages of the use of cDNA?

What are gene probes? How might they be used in diagnosis?

Distinguish between an inducible and a repressible operon. Know the workings of the examples we discuss in class

How do microbes (bacteria) maintain genetic diversity without sexual reproduction