Prokaryotic genomes and organelles (12)

12

Membrane organization

Cellular membrane-Cell wall

Membrane organization of Gramm negative bacteria

Cellular membrane-Cell wall-Outer membrane

Bacterial organelles…

do not have a membrane

What does that particularity allow?

Translation (ribosome) can occur on RNA before transcription (mRNA) has finished

Shape of bacterial chromosomes

Circular

Number of bacterial chromosomes

1 but 10% contain more

Distribution of replisomes

1 for each half of the chromosome

Why are highly transcribed genes oriented in the same direction as the replication fork progression?

To avoid conflicts between replisomes

Why is bacterial DNA gene rich? (2)

1. Little intergenic regions

2. No introns

Operons

Gene groups that share a common promoter

Polycistronic mRNA

Operons that are transcribed together

Histones for bacteria

Gyrase

Function of gyrase

Introduce torsion (negative supercoiling) to compact DNA

Nucleoid

Chromosome+Proteins

Origin of DNA in a nucleoid

Center of poles

Mitochondria and chloroplasts

Originally membrane free but became endosymbionts through endocytosis

Endocytosis of bacterium capable of oxydative phosphorylation

Mitochondrial genome

Endocytosis of bacterium capable of photosynthesis

Chloroplast genome

Organellar DNAs and bacteria

Similar bc circular and no introns

Length of mtDNA

Short (16k and 37 genes)

Where do the proteins stay after translation of mtDNA?

Within the mitochondria

Length of cpDNA

Long (200k and 100-200 genes)

Bacterial endosymbionts

Insects that eat from plant saps

Blood-feeding flies

Fact ab obligate bacterial endosymbionts

They undergo a reduction of their genome

Where is the majority of mitochondria and chloroplast proteins coded?

In the nucleus (movement through evolution)

How is mtDNA passed down?

Through cytoplasmic inheritance (not predictable)

mtDNA codons

More than in DNA

Mutation in mtDNA

Related to aging in mammals