IB Biology D2.2 – Gene Expression and Epigenetics (HL)

What is gene expression? (HL)

The mechanism by which information in genes has effects on the phenotype.

What are the most common stages of gene expression? (HL)

Transcription, translation, and the function of the protein product.

How can a protein product affect phenotype? (HL)

By functioning as a molecule such as an enzyme.

How is transcription regulated at the DNA level? (HL)

By proteins binding to specific base sequences in DNA.

What is a promoter? (HL)

A DNA sequence where transcription begins.

What is an enhancer? (HL)

A DNA sequence that increases transcription when bound by proteins.

What are transcription factors? (HL)

Proteins that bind to DNA and regulate transcription.

How can translation be regulated after transcription? (HL)

By controlling the degradation of mRNA.

How long can mRNA persist in human cells? (HL)

From minutes up to days.

What enzymes break down mRNA? (HL)

Nucleases.

What is epigenesis? (HL)

The development of patterns of differentiation in a multicellular organism.

Do epigenetic changes alter DNA base sequences? (HL)

No.

What is altered by epigenetic changes? (HL)

Phenotype but not genotype.

What is the genome of a cell? (HL)

All the genetic information of an organism.

What is the transcriptome of a cell? (HL)

All the RNA transcripts produced by the cell.

What is the proteome of a cell? (HL)

All the proteins produced by the cell.

Why do different cells differentiate differently? (HL)

Because they express different sets of genes.

How does methylation of cytosine in a promoter affect transcription? (HL)

It represses transcription.

How can methylation of histones affect transcription? (HL)

It can repress or activate transcription.

What is epigenetic inheritance? (HL)

Heritable changes in gene expression without changes to DNA sequence.

How can epigenetic tags be inherited? (HL)

If they remain during mitosis or meiosis.

Give examples of epigenetic tags. (HL)

DNA methylation and histone modification.

How can the environment affect gene expression? (HL)

By altering epigenetic tags on DNA.

Give an example of an environmental factor affecting methylation. (HL)

Air pollution.

What happens to epigenetic tags during gamete formation? (HL)

Most are removed, but not all.

How can incomplete removal of epigenetic tags be demonstrated? (HL)

By phenotypic differences in tigons and ligers.

What do monozygotic twin studies investigate? (HL)

The effects of the environment on gene expression.

Give an example of a hormone affecting gene expression. (HL)

A hormone acting as a signalling molecule.

Give an example of a biochemical affecting gene expression. (HL)

Lactose or tryptophan in bacteria.