Prokaryotic genomes and organelles

lecture 12

Where does bacteria exist?

EVERYWHERE

they are the most diverse group of organisms

What does bacteria contain?

cell wall that surrounds a cellular membrane

gram negative bacteria contains this

non membrane bound organelles

chromosomes in contact with cytoplasm

coupled transcription/translation → ribosome translates RNA before transcription finishes

What kind of chromosome does bacteria contain?

single circular chromosome with a single origin of replication (each half replicated by one replisome)

how are highly transcribed genes oriented in bacterial chromosomes?

in the same direction as the replication fork to avoid conflicts 

what is the organization of genes in bacterial chromosomes?

they are compact genes 

lack introns 

few intergenic regions 

are grouped in operons which share a common promoter and are transcribed together = polycistronic mRNA (multiple genes of translation)

Does bacteria have histones/nucleosomes?

No

what binding proteins do bacteria use?

HU, IHF instead of histones

What is gyrase used for?

its their version of topoisomerase which introduces torsion 

What generates loops in bacterial DNA?

SMC proteins

What is a nucleoid?

where the chromosome region is located

DNA + protein 

Where is the origin of replication located?

centre of the cel or at the cell poles

why is the mitochondria and chloroplast important?

play roles in respiration and photosynthesis respectively 

What were they originally and what did they become?

they were free organisms that were endocytose and became endosymbionts 

What is the composition of mitochondria and chloroplasts?

• circular

• lack introns 

• gene products resemble prokaryotic RNA’s and proteins 

What happens to the products made by the mitochondria?

they stay within the mitochondria

who proposed the endosymbiosis hypothesis?

Lynn margulis - she proposed that mitochondria and chloroplasts originated from free living bacteria 

since the cell doesn’t not have enough energy to create energy on its own, it recognized that the mitochondria did his and engulfed it 

What are the closest relatives of the recipient cell that generated the first eukaryotes?

lokiarchea

Examples of endosymbiosis

• insects that eat from plant saps - helps then produce nutrients that lack in their diet

• solar powered sea slugs steal chloroplasts from algae 

• corals and phototrophic dinoflagellates

What do obligate endosymbiont bacteria undergo?

they undergo a reduction of their genome

they must have a relationship because their genome is too small and can’t produce what they need to survive 

What of their own do mitochondria have?

ribosomes

Explain the inheritance of mitochondria in daughter cells (inheritance, distribution, make what)

maternal inheritance through the cytoplasm

they are distributed every among daughter cells

distribution of mitochondria is random

needed to make ATP

what are mutations in mtDNA related to?

aging in mammals

defective DNA polymerase in mice lead to aging