MCB Ch. 9

The study of what genes are, how they carry info, how info is expressed, and how genes are replicated

a segment of DNA that encodes a functional product, usually a protein

Structure containing DNA that physically carries hereditary info: chromosomes contain the genes.

All the genetic info in a cell

Eukaryote: Mitochondria, plasmids, nucleus

Prokaryote: Plasmids, chromosomes

Vertical: parent → offspring

Horizontal: in the same population/generation

• initiation - RNA polymerase binds to the promoter and DNA unwinds

• elongation - RNA is synthesized. DNA that has been transcribed rewinds.

• termination - Transcription reaches the terminator. RNA and RNA polymerase are released. DNA helix re-forms

DNA Ligase

• mRNA

• tRNA

• rRNA

in ribsomes

codons

Start: AUG

End: UAA, UAG, UGA

Protect genetic code from harmful mutations

The inducible operon

• regulatory gene

• promoter

• operator

• structural genes

encodes a repressor/inhibitor gene

enables a gene to be transcribed. is recognized by RNA polymerase

initiate transcription

This is where the repressor binds

contains sequences of DNA corresponding to the amino acids of a protein that will be produced. (codes for a protein)

A repressible operon

• rapid reproduction

• mutation

• genetic recombination

• conjugation

• transformation

• transduction

• A cell with pili will form a bridge with another cell to transfer DNA

• direct

• naked DNA (free donor DNA fragment) in the environment is taken into the cell.

• indirect

• A bacteriophage takes up the donor’s cell DNA and when it enters another cell, it will incorporate the Donor bacteria DNA into the recipient’s DNA (lysogenic cycle)

• indirect

Generalized:

• The virus only has bacterial DNA in it. Does not give viral DNA to the recipient.

• bacteriophages can pick up any portion of the host's genome.

Specialized:

• New, replicated virus has both viral and bacterial DNA.

• bacteriophages pick up only specific portions of the host's DNA.

A cell with a pilus (F+) attaches to a cell without a pilus (F-). It transfer one strand of F plasmid over to the recipient. Now both are F+ and have pilus

• plasmid jumps into the chromosome and becomes a part of it

• when the chromosome duplicates, the plasmid and part of the chromosome is transmitted to a new cell (conjugation).

• The plasmid/chromosome hybrid incorporated into the recipient chromosome

High-frequency transfer

• A gene (insulin) is integrated into a plasmid by Ligase.

• Plasmid enters a cloning host cell (E.coli) through transformation. This cell lacks any extra plasmids that could complicate the gene expression of the plasmid.

• Take and keep the cells that have the recombinant plasmid.

• As cells multiply, the plasmid also replicates. Each cell contains the gene. (E. coli cells can now produce human insulin)

• There can be billions within a few hours

• Recombinant strain is maintained in culture for production purposes

• amplifies the number of copies of DNA

• rapidly increased the amount of DNA in a sample

Steps

1. Denature - breaks double helix into two strands

2. Anneal - a primer is added to each strand for DNA synthesis

3. Extension: the DNA strand is extended

Continues until there is a lot