Bacteria Flashcards
what does bacteria need
tryptophan (Trp)
where does Trp come from
from food, but can be made if food is poor- to make it 5 enzymes are needed- this costs energy, so bacteria shouldn’t waste energy if it is present in food
what does the Trp operon make
it only makes enzymes when the Trp levels are low
what are operons
a bacterial gene cluster controlled by a single promoter e.g Trp operon
what controls operons
this is controlled by a repressor- it binds to the promotor and blocks transcription
how does gene regulation in eucaryotes differ from procaryotes
- 3 RNA polymerase instead of 1
- regulation at distance
- Effects due to DNA packing
- need for general transcription factors
how many RNA polymerases are in eucrayotic cells
3
what is the 1st RNA polymerase
most rRNA genes
what is the 2nd RNA polymerase
all protein coding genes
what is the 3rd RNA polymerase
tRNA genes, 5S rRNA gene and genes for some small structural RNAs
what are most genes transcribed by
RNA 2
What is pituitary dwarfism
a lack of a growth hormone and mutations in growth hormone gene. If they lack several hormones they have a mutation in transcription factor- Pit-1
where is DNA found
the nucleus
where are proteins found
the cytoplasm
why are messengers needed for DNA and proteins
to carry it from the nucleus to the cytoplasm
why is RNA a messenger
as it is structurally similar to DNA and abundant in the cytoplasm and can be found in the nucleus
what sugar does RNA and DNA have
RNA - ribose sugar
DNA- deoxyribose sugar
why is RNA less favoured for storing permanent info
- ribose sugar less capable of forming long chains
- double strand DNA favours repair and increases stability
what Is converted in transcription
DNA ->RNA using mRNA from template DNA strand
what is the template strand
the coding strand as its sequence is equivalent to the RNA product (but the 3’ to 5’ strand used as a template for base pairing)
is transcription quick
it is quicker than DNA replication as it has no proof-reading and the helix rewind behind RNA transcription, displacing it
how is DNA transcribed into RNA
by RNA polymerase- it adds nucleotides on by one to the RNA using an exposed DNA strand (3’ 5’) as a template
what is the resulting RNA after it is transcribed
it is singe-stranded with complementary copy of one of 2 DNA strands. The incoming nucleotides are triphosphate and the energy in their phosphate bonds is the driving force to polymerisation
