?????relative sizes of typical mitochondrial, chloroplast and nuclear
- The nuclear genome has the largest genome by far (orders of magnitude bigger), the chloroplast
has much fewer base pairs (about 200 kb) with the mitochondrion having the fewest base pairs
(about 16 kb)
- The typical prokaryote E. Coli has a much bigger genome than that of the organelles. This
suggests that lateral gene transfer has occurred, making the genome in the organelles much
smaller than expected for a typical prokaryotic cell
-Clamey has 100 thousand kilabases (100 thousand base pairs)
- linear chromosomes
- chloroplast has dna in it, only 200 kilabases.
-Vaucheria litorea (chloroplast genome)
- its an algae
-170 genes, 115kb of dna
- this genomes has gone from 5000 kilabases down to 115 over
-We make only about a dozen proteins but they put 37 genes, why?
-Why is there a disconnect b/w number of gnes and number of proteins?
- not all protein coding genes (junk dna, dead)
- If gnes don’t code for proteins what do they code for? All rna’s are made by
transcrption of genes. Each of different rna’s have own gene. Might be protein
coding gene or might be rna coding gene. Most genes code for rna. Why?
****rubisco structure and assembly from components coded by different
- the enzyme usually consists of two types of protein subunit, called the
large chain L and the small chain S. The large-chain gene is part of the
chloroplast DNA molecule in plants.
possible reasons why modern organelle genomes have become
dramatically smaller over evolutionary time
- Thye’ve evolved to be very specific, they only carry certain processes so they
don’t need any gnes? Where do they go?
- genomes have been deleted.
- Hosts in which their mitochondria has suffered a mutation and deletion,
those genomes will be easier to replicate (selective advantage) selection
favouring organelles getting rid of all the genes they can. - Some genes are useful for free living bacteria but when mitochondria and chloroplasts were
absorbed into the early eukaryote, some genes became redundant (like those for flagella and
Selection then favoured organelles with streamlined genomes because they are
more efficient and use less energy to replicate and translate their genomes
- Why would a cell want two copies of everything? Why would genes take two
copies for mito and nucleus (a lot of redundancy) .
possible reasons why genes have moved to the nucleus from organelles
over evolutionary time
1. Coordinated control between the nucleus and the organelles
- why in general want to get dna out of mitochondria and chloroplast?
2. Mitochondria and chloroplast are involved in electron transport and oxygen
metabolism that generates reactive oxygen species. Oxygen + electron gives
reactive oxygen species.
- These organelles are sites of ROS production and ROS is very reactive
and very mutagenic and creates all kids of damage in dna. Makes sense
to get dna out of the mutagenic oxygen.- what denis taught but haffies
3. RNA can be edited in the nucleus though it cannot be edited in the organelles (no separation
between DNA and ribosomes so translation directly after transcription)
- organelle genomes are