Microbial Genetics
Introduction to Genetics and Genes: Unlocking the Secrets of Heredity
Reference: https://sites.google.com/site/rccmicrobiology/chapter-9-microbial-genetics
- The Levels of Structure and Function of the Genome
- Genetics: study of inheritance, or heredity, of living things.
- Genome: sum total of genetic material of a cell.
- Chromosome: discrete cellular structure composed of a neatly packaged elongate DNA molecule.
- Eukaryotes condense their DNA around histones proteins.
- Bacteria chromosome is condensed by means of histone-like proteins.
- Most bacteria have a circular chromosome.
- Gene: information packet that is provides information for a certain cell function.
- Specifically, segment of DNA that contains the necessary code to make a protein or RNA molecule.
- Nucleotide: basic unit structure of DNA.
- A molecule made of phosphate, deoxyribose sugar, and a nitrogenous base.
- Nitrogenous bases: purines & pyrimidines.
- Purine combines with purine and pyrimidine combines with pyrimidine.
- Purine: (A)denine bonds to (T)hymine.
- Pyrimidine: (G)uinine bonds to (C)ytosine.
- Anti-parallel Arrangement
- DNA sequence goes from 3' to 5' then on the other side 5' to 3'.
- Model:
- (3') TAC CCT AGA CGA ATT TTT TCC (5')
- -------enzyme------->
- (5') ATG GGA TCT GCT TAA AAA AGG (3')
- New DNA anti-parallel strand will be:
- (5') ATG GGA TCT GCT TAA AAA AGG
- Significant of DNA Structure
- Nitrogen bases influence DNA in two major ways:
- (1) Maintenance of code during reproduction.
- (2) Providing variety.
- DNA Replication: genetic program duplicated and passed on to each offspring.
- DNA Replication
- Semi-conservative model: one strand is used to create a build a complete DNA strand for the daughter cell.
- Replicon: origin of replication of DNA, commonly a single origin for a circular chromosomal DNA.
- Palindrome: initiation site for replication.
- Process
- 1. Helicase unwinds helix.
- 2. Primase: makes RNA primer.
- 3. DNA polymerase-3 (building DNA copies).
- Continuous synthesis: leading strand.
- Discontinuous synthesis: lagging strand.
- 4. DNA polymerase-1
- Replaces RNA primers with DNA.
- 5. DNA Ligase
- Joins lagging strand fragments, okazaki fragments, together.
- Operon: specific collection of genes.
- Use coordinated set of control genes: regulators, promoters, and operators).
- Induced: operon turned on by the substrate of the enzyme for which the structural genes code.
- Repressed: operon turned off by the product its enzymes synthesize.
- Mutation: permanent, inheritable
Reference: https://sites.google.com/site/rccmicrobiology/chapter-9-microbial-genetics