DNA and RNA synthesis Flashcards
what is static
genome
- every cell in our body has a copy of the same genome
a cell is
dynamic
repsonds to external conditions
most cells follow a cell cyle of division
psuedogenes
related to real genes
contain biological and evolutionary histories within their sequences
what is junk DNA used for
1) Landing sports for proteins that influence gene activity
2) Strands of RNA with myriad roles
3) Places where chemical modifications silence stretches on chromosome
what is gene regulation infleunced by
multiple stretches of regualtory DNA
- non coding RNA
what does mRNA do
contains info to make one single polypeptide chain
DNA bases
adenine
guanine
cytosine
thymine
RNA bases
adenine
guanine
cytocine
uricil
uricil vs thyine
simular structure
both bind to adenine via hydrogen bonds
identical shapes where it matters
transcription deficnition
process where information in a gene in a DNA strand is is transferred to an RNA molecule
2 strands in transcripton
coding strand
template strand
types of RNA
mRNA tRNA non coding RNA small nuclear RNA small nucleoalr RNA micro RNA
which RNA regulate expression
non coding RNA
small nuclear RNA
small nucleoalr RNA
micro RNA
mRNA
different sizes reflecting size of polypeptide
needed by all cells, spefcif for types of cells
rRNA
build ribosomes, (requried for synthesising protiens by trnaslating mRNA
different kinds and eukaroytes of rRNA and their purpose
18s
- make up small subunit of riosome alongside other protiens
28s
5.8s
5s
- one of these with45 other protiens make up the large subunit
what is the s related to in eukaryotes
sedimentation rate, related to mass and shape
tRNA
each has 20 aa at 3’ end
fucntion of non coding RNA
modify protien levels by mechanisms independant of trnascrpiton
- ncRNA play major roles in cellular physiology, development,
metabolism and are implicated in disease process
what are small nucelar RNA part of
spilceosome
what is transcription
process where information in a gene in a DNA strand is transferred to an RNA molecule§
what does RNA polymerase do
picks the correct DNA strand and finds the start
what are the 3 types of eukaryotes
1) Polymerase I
- Nucleolar region of nucleus
- transcribes large ribosomal RNA
2) Polymerase II
- mRNA precursors
3) Polymerase III
- small RNAs (tRNA)
- regulatory RNAs
polymerase II
- composed of several subunits
- requires several accessory proteins
- All added to the complex in a defined order to initiate and carry out transcription
Enzyme wraps around both strands - big enough to enclose both the promotor and beginning of the gene
enhancers and promotors
DNA sequences which can control efficiency and rate of transcription
- found on the same molecule as the gene, referred to as cis acting elements as they’re on the same side
promotor
necessary to start transcription
- usually on the 5’ side of gene to be transcribed
activators
proteins that facilitate looping
repressors
inhibit looping
what happens during transcription steps
- unwinds DNA
- Splits them apart
- bubble moves down the DNA, closing up once the RNA has been produced
- RNA polymerase moves down the gene
- Places a cap* on the 5’ end to stabilise the mRNA
- alternative splicing can occr
- PolyA tail on the 3’ end added
capping
Takes place during transition from transcription initiation and elongation
- protects from degradation
- serves as assembly point for proteins needed to recruit small subunit of ribosomes to begin translation
alternative spilcing
- alternative selection of splice sites within pre mRNA
- leads to production of different mRNA isoforms of a gene
what do splicoesomes regonsei
borders between introns and exons
types of splicosomes
major and minor (remove only 0.5%)
function of spliceosome
1) Recognition of intron/exon boundaries
2) Catalysis of cut and paste reactions which remove non coding introns and stitch flanking exons back together
mutations of a spliceosome
- mis splicing =rapid degermation of mRNA
- mis regulation of splicing factor levels (cancer)
what do small nucleolar RNA do
- help make ribosomes by cutting large precursors of eg 28s
- also implicated in alternative splicing of pre-mRNA
- template for synthesis of telomers
micro RNA
- regulate gene function post transcriptionally
- bind to mRNA and cause degradation (inhibits protein synthesis)
- 18-25 nucleotides
- involved in regulation of developmentally timed events
- exhibit tissue specific expression
- implicated in cancer development
