Microbio - CH 9

Introduction to microbial genetics

define genome.

sum of genetic material (DNA) in a cell

Where can you find microbial genomes?

Chromosomes, some appear in non chromosomal sites like mitochondria, chloroplasts, plasmids

What does DNA gyrase do?

coils the chromosome into a tight bundle by introducing reversible series of twists into the DNA molecule.

DNA gyrase is found in ____

Prokaryotes

Define genotype.

All of the genes in an organism constitute its distinctive genetic makeup

define phenotype.

The expression of the genotype creates traits (certain structures or functions)

what do structural genes do?

genes that code for proteins

What do regulatory genes do?

genes that control gene expression

What 3 components does a nucleotide contain?

Deoxyribose sugar, phosphate group, nitrogenous base (AGCT)

Which carbon do nitrogenous bases covalently bond to?

1’ C

How many hydrogen bonds exist between Adenine and Thymine

2

How many hydrogen bonds exists between Cytosine and Guanine?

3

What forms the sugar phosphate backbone?

nucleotides covalently bonded together

What does the 5’ end of contain?

phosphate group

what does the 3’ end contain?

sugar hydroxl group

what direction must a DNA strand be built?

5’→3’

How would you describe the structure of DNA (double stranded)

Antiparallel

How is gentic information stored?

In the sequence of the bases in DNA

What does RNA participate in?

Gene expression and Protein Synthesis

What did Fredrick Griffith come up with?

bacteria can transfer genetic information through a biochemical agent

What did Avery, Macleod, and McCarty discover?

• Discovered that DNA was the gentic factor that caused the death of Griffith’s mice not protein.

• Used enzymes (DNase & Proteases) to prove it.

What did Erwin Chargaff discover?

What DNA was made of.

• determined the ratios of the 4 DNA nucleotides (G-C, A-T)

• provided evidence of the base pairing rules in DNA

How many origins do prokaryotes have?

1

How many ways does a prokaryote replicate?

2 ways

What is meant when we say, DNA is semi-conservative?

each of the two molecules created contains one of the original strans paired with a newly synthesized strand

What nucleotides are rich in prokaryotes?

A-T

Why are prokaryotes A-T rich?

because they only contain two hydrogen bonds, so it is less energy to break them apart.

Which end are nucletides added on?

3’ end

Why can we only add on the 3’ end?

becuase it contains an OH- group and it comes off during dehydration synthesis.

What does helicase do?

unwinds and unzips DNA double helix at the Origin (replication fork)

What do binding proteins do?

keep the double helix seperated

what does primase do?

builds an RNA primer in a 5’→3’ direction from the antiparallel template

What does DNA polymerase III do?

adds nucleotides to the RNA primers on a 5’ to 3’ direction using the same antiparallel 3’ to 5’ template strand

What is the lagging strand?

synthesized continuosly in a 5’ to 3’ direction of new growing strand

what is a lagging strand?

synthesized discontinously in a 5’ to 3’ creating short segments called okazaki fragments

What does DNA polymerase I do?

replaces RNA primers with DNA

What does DNA ligase do?

joins all DNA fragments together

What does gyrase do?

supercoils the replicated DNA

What is gene expression?

genes are switched on or off as and when they are needed

What does it mean when a gene is switched on?

it is expressed, transcribed and translated byb protein syntheis

rRNA + protein =?

ribosome

what does tRNA do?

transfers a specific amino acid to the ribosome

what does mRNA do?

a messenger for the genetic message

Where does protein synthesis take place in prokaryotes?

cytoplasm

What does the promoter region contain?

TATA box

What is the first step in transcription?

the gene to be transcripted is exposed

What is the second step in transcription?

the promoter region (sequence is flagged)

What is the third step in transcription?

RNA polymerase binds to the promoter

What is the fourth step in transcription?

RNA polymerase unzips the DNA one small area at a time

What is the fifth step in transcription?

RNA polymerase transcribes using only one strand of the DNA

What is the sixth step in transcription?

RNA is built in a 5’ to 3’ direction using the DNA (3’ to 5’) as a template

What is the seventh step in transcription?

complemenatry RNA nucleotides are added using GC-AU base pairing rules. Uracil is used as the complemntary base to Adenine.

What is the eigth step in transcription?

RNA polymerase reaches and recognizes the gene termination site

What is the ninth step in transcription?

RNA polymerase releases the RNA transcript - varies from 100-1200 bases long