DNA and RNA synthesis Flashcards by Cassie Lee

what is static

genome

- every cell in our body has a copy of the same genome

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a cell is

dynamic
repsonds to external conditions
most cells follow a cell cyle of division

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psuedogenes

related to real genes

contain biological and evolutionary histories within their sequences

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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

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what is gene regulation infleunced by

multiple stretches of regualtory DNA

- non coding RNA

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what does mRNA do

contains info to make one single polypeptide chain

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DNA bases

adenine
guanine
cytosine
thymine

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RNA bases

adenine
guanine
cytocine
uricil

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uricil vs thyine

simular structure
both bind to adenine via hydrogen bonds
identical shapes where it matters

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transcription deficnition

process where information in a gene in a DNA strand is is transferred to an RNA molecule

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2 strands in transcripton

coding strand

template strand

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types of RNA

mRNA
tRNA
non coding RNA
small nuclear RNA
small nucleoalr RNA
micro RNA

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which RNA regulate expression

non coding RNA
small nuclear RNA
small nucleoalr RNA
micro RNA

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mRNA

different sizes reflecting size of polypeptide

needed by all cells, spefcif for types of cells

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rRNA

build ribosomes, (requried for synthesising protiens by trnaslating mRNA

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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