MCB Ch. 9

Define Genetics

Define Genetics

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

Define Gene

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

Define Chromosome

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

Define Genome

All the genetic info in a cell

Name the locations of genetic materials for:

• Eukaryotic cells

• Prokaryotic cells

Eukaryote: Mitochondria, plasmids, nucleus

Prokaryote: Plasmids, chromosomes

Vertical vs. Horizontal genetic flow

Vertical: parent → offspring

Horizontal: in the same population/generation

Describe the steps of transcription

• 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

What holds Okazaki fragments together?

DNA Ligase

types of RNA:

• mRNA

• tRNA

• rRNA

Where does Translation occur?

in ribsomes

mRNA is translated in:

codons

List the start and end codons

Start: AUG

End: UAA, UAG, UGA

Redundancy of codons help with what?

Protect genetic code from harmful mutations

What operon is usually off but can be triggered to turn on?

The inducible operon

List the main parts of an Operon:

• regulatory gene

• promoter

• operator

• structural genes

What does the regulatory gene on an operon do?

encodes a repressor/inhibitor gene

What does the promoter on an operon do?

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

What does RNA polymerase on an operon do?

initiate transcription

What does the operator on an operon do?

This is where the repressor binds

What is the role of structural genes on an operon?

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

What is an operon that is usually on but can be turned off?

A repressible operon

Factors that contribute to prokaryotic genetic diversity

• rapid reproduction

• mutation

• genetic recombination

Types of horizontal gene transfer

• conjugation

• transformation

• transduction

Explain conjugation

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

• direct

Explain tranformation

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

• indirect

Explain transduction

• 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 vs. Specialized Transduction

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.

F+ x F- cell

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

High-frequency transfer (HFr)

• 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

How can antibiotic resistance spread?

High-frequency transfer

Explain how Recombinant DNA technology works

• 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

What is a PCR (Polymerase Chain Reaction)?

• 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