1 - Nuclear Genomes

Question 1

Give four characteristics of bacterial, archaeal and organellar genomes that differs form nuclear genomes

Answer 1

• Often circular, sometimes linear
• High gene density, streamlines, and lack repetitive DNA
• Replication, transcription and translation in the same compartment
• Genes subject to little or no RNA processing

Question 2

How many more microbes are there than non-microbes?

Answer 2

An absolutely ridiculous amount.

The only three categories of organisms that aren’t are:

Unikonts

• Metazoa
• Fungi

Plantae
- Land plants

Question 3

How is the nuclear genome organized?

Answer 3

• Linear DNA molecules that associate in very specific manner with a large number of proteins (chromatin, each DNA/protein unit is a chromosome)
• Number and sizes of chromosomes vary greatly with species ( typically between 100,000 bp and several million bp in size)
• Chromatin is highly dynamic

Question 4

List some covalent modifications that DNA and protein can undergo

Answer 4

DNA

• Methylation
• Hydroxymethylation

Proteins

• Methylation
• Acetylation of histones (promotes loose chromatin structure that permits transcription)

Question 5

Give the two types of heterochromatin

Answer 5

Constitutive heterochromatin: eg. telomeres, centromeres

Facultative chromatin: epigenetic silenced

Question 6

What is the biggest difference in content between prokaryotic and eukaryotic genomes?

Answer 6

Gene density

Extra-genic (eg. transposon-based repeats, heterochromatin and other sequences) DNA is scarce in prokaryotes/organelles but highly abundant in nuclear genomes