genetics

Microbial Genetics

Genetics

Genetics: field of biology that studies genes and their inheritance

Gene

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

Gene

Gene Vs. Genomes

Genome = All of the genetic material (DNA) in a cell.
Prokaryotic cell has only one genome located in the nuclear area.
Eukaryotic cell has 2 genomes
Nuclear genome
Mitochondrial genome
If not specified, “genome” usually refers to the nuclear genome.


Gene Vs. Genomes
In human beings genes constitute only 3 % of the human genome.
The remaining 97 % of the genome – have yet no known functions! These regions are called non-coding regions.
Genome = Coding regions (genes) + non-coding regions.

Genetics Vs. Genomics

Genetics is the study of single specific, individual genes in isolation and their role in inheritance

e.g. "monogenic" diseases such as sickle cell anaemia and cystic fibrosis, caused by an error in a single gene

Genetics Vs. Genomics

Genomics is the study of all the genes in the genome and the interactions among them and their environment (or non-genetic factors such as a person's lifestyle)
Improve understanding of complex diseases such as diabetes, heart disease, and asthma

Genetics Vs. Genomics

Genetics is the study of single specific, individual genes in isolation and their role in inheritance
e.g. "monogenic" diseases such as sickle cell anemia and cystic fibrosis, caused by an error in a single gene.

Genotype Vs. Phenotype

• "Genotype" is an organism's full hereditary information.

• "Phenotype" is an organism's actual observed properties, such as morphology, development, or behaviour

Genotype Vs. Phenotype

Structure and Function of Genetic Material

Genetic Material = DNA or RNA

• In the vast majority of organisms, genetic material is DNA (deoxyribonucleic acid)

• In some viruses , genetic material is RNA (ribonucleic acid)

• Nucleotides

• Phosphate group


• Pentose sugar

• Nitrogenous base

Genetic Material: Basic Building Units

Structure of DNA
Double stranded (double helix)

Adenine (A), thymine(T), cytosine(C) and guanine(G)

"Backbone" is deoxyribose-phosphate

Strands held together by hydrogen bonds between AT and CG

5’ to 3’ (strands are anti-parallel)

Complimentary base pairing
A-T • G-C



Hydrogen bonds

DNA Replication

Bacteria have closed, circular DNA

E. coli

4 million base pairs
1 mm long (over 1000 times longer that actual bacterial cell)
DNA takes up around 10% of cell volume

DNA Replication

Helicases

Single stranded DNA binding protein


DNA Replication

Polymerase III

5’
3’

DNA Replication

RNA Primase

1
2
3
Synthesizing leading strand starts by binding a short RNA segment (primer) to single DNA template by RNA primase in 5’ to 3’ direction.
DNA template

Finally, polymerase I, a cousin of polymerase III, replaces RNA primer with DNA.

DNA Replication
Polymerase III finishes the building up of leading strand continuously in 5’ to 3’ direction

DNA Replication

DNA replication

In the synthesis of the lagging strand, the helix uncoiling occurs in the opposite direction to which polymerase III works. Therefore, the process has to be done in pieces (not-continous). These pieces are called Okazaki fragments.
RNA primers


DNA Replication

Polmerase III synthesizes short DNA segments between RNA primers.

Polymerse I replaces RNA primers with DNA.

DNA replication

Finally, DNA ligase enzyme binds DNA pieces together to create lagging strand

DNA replication