LEC 10: Genetics and Epigenetics

4 steps of gene expression

1. DNA partially unravels, exposing the structural gene for transcription.

2. A strand of mRNA is transcribed from the exposed DNA and carries the genetic code to the cytoplasm.

3. In the cytoplasm, mRNA attaches to a ribosome, which translates codons into amino acids with the help of transfer RNA.

4. Upon reaching the end of the mRNA strand, a codon signals the ribosome to release the completed protein.

Function of DNA

DNA is the recipe that tells cells how to build proteins

The 4 nucleotide bases that can make up DNA

• Adenine (A)

• Thymine (T)

• Guanine (G)

• Cytosine (C)

How proteins are built from genes, and mRNA’s role

• Genes are organized into codons. Each codon is 3 nucleotides long and ‘codes’ for a specific amino acid.

• During transcription, a gene is copied into a strand of mRNA.

• The sequence of each mRNA strand matches the DNA sequence of that gene.

• During translation, mRNA strands are translated into proteins by ribosomes.

Optogenetics

A transgenic technique that combines genetics and light to control targeted cells in living tissue

CRISPR

A gene editing tool used to copy and paste genes

Epigenetics

The study of changes in gene expression related to experience

The role of the environment in epigenetics

• Can influence gene activity by regulating the behaviour of epigenetic writers and erasers

• addition/removal of acetyl and methyl groups can help the brain respond and adapt to environment

Histone acetylation

An epigenetic mark that relaxes/loosens the chromatin and increases gene transcription (OPEN)

Histone methylation

An epigenetic mark that tightens/condenses the chromatin and decreases gene transcription (CLOSED)