Lecture 04 — The Central Dogma of Molecular biology

Outline the central dogma & describe information flow

Core idea: Biological information flows in one direction:
DNA → RNA → Protein

Key processes:

• Transcription: DNA → RNA

• Translation: RNA → protein

• Replication: DNA copying itself

• Reverse transcription: RNA → DNA (only virus)

what is The Omics

the collectiv study of an entire field or biomolecule within the organism

Define genome

Genome:
All DNA in an organism. Every nucleated cell contains the full genome.

• the DNA blueprint for every part of an organism

• chromosome > genes >DNA (comprised of nucleic acid)

• vary in makeup, count, structure between organisms, species, within species, between cells

define transcriptome

Transcriptome:
All RNA in a cell (mRNA, rRNA, tRNA, miRNA, siRNA).

• two different cell types > different transcriptome

• same cell types > same transcriptomes

define Proteome:

All proteins expressed in a cell.

• two different cell types > different proteome

• same cell types > same proteome

Why genome, transcriptome and proteome differ:

• Different cell types express different genes.

• Same genome → different transcriptomes → different proteomes

Differences in size & construction between bacterial and eukaryotic genomes

Eukaryotic genomes:

• Large (10 Mb–150 Gb).

• Linear chromosomes, wrapped around histones.

• chromosomes condensed into chromatin, wrapped around histone proteins

Prokaryotic genomes:

• Small, typically 150 kb–15 Mb.

• Circular chromosomes, no nucleus.>no histones

benefit of having small chromosome: faster DNA replication > faster cell division

Complexity note:
Genome size or chromosome number does not correlate with organism complexity.

Describe the universal genetic code

Universal: Shared by almost all organisms.
Triplet: 3 nucleotides = 1 codon.
Non-overlapping: Each base belongs to only one codon. (5>3)

Redundancy: Many amino acids have multiple codons.
Start codon: AUG (Met).
Stop codons: UAA, UAG, UGA.

what are start codon and stop codon ?

Start codon: AUG (Met).
Stop codons: UAA, UAG, UGA.

type of DNA/ protein mutation