DNA and RNA Flashcards
how does one go from a gene to protein
(central dogma)
- genes composed of DNA which is transcribed into RNA and translated into protein
DNA is capable of _____ making it able to be passed onto other generations
what is the basic unit of DNA and its structure
- basic unit = nucleotide
- composed of deoxyribose sugar, bonded to phosphate and a nitrogenous base
- base can be purine or pyrimidine
what are the pruines and what are the pyrimidines
- purines - adenine and guanine ( 2 rings)
- pyrimidines = cytosine and thymine )1 ring)
what forms the chain between nucleotides
phosphate and sugar
- nucleotide bases are off to side and form the h bonds
how is double helix held together, what is the structure
- via hydrogen bonds
- sugar phosphate on outside and nitrogenous bases on inside h bonding
- T forms 2 h bonds with A
- G forms 3 H bonds C
- antiparallel arrangement
how does DNA strands separate to prepare for replications
- uncoiled by topoisomerase and DNA helicase breaks the h bonds
- opening of DNA known as replciation forl
replication is referred to as _____
semi conservative
what is responsible for synthesis of daughter strand, how does it work
- DNA polymerase
- reads parent strand and creats complementary antiparallel daughter strand
- have leading strand (continuously synthesized adding nucleotides to exposed 3’ end) and the lagging strand (5’ end is exposed so forms okazaki fragments DNA ligase stitches the fragments together)
what is the difference between RNA and DNA
- ribsoe sugar
contains uracil not thymine
usually single stranded
where is RNA found? what are the major types
found in nucelous and cytoplasm
- major types are mRNA, tRNA and rRNA
describe mRNA
- carries the complement of the DNA sequence (but T sub for U)
- transports compliment from nucleous to the ribosomes for proteins nthesis
- mRNA made of ribonucelotides complementary to template strand of DNA
- one mRNA strand codes for one polypeptide
describe tRNA
- small RNA mol in cytoplasm
- assis with translation of mRNA nucleotide code into a seq of amino acids
- helps by bringing the amino acids coded for in the mRNA sequence to ribosomes during protein syn
- one end of tRNA has anticodon and other end has aa
- each aa has its own aminoacyl-tRNA synthetase which has an active site that binds to both the amino acid and its corresponding tRNA to cat attachment
*there is at least one type of tRNA for each aa
describe rRNA
- ribosomal RNA is a structural component of ribosomes and is most abundant of all RNA
- mRNA seq passes thru two subunits of rRNA and is translated into amino acids
*rRNA is syn in nucleolus
what is transcription
- proces by which info coded by DNA is transcribed into a strand of mRNA that leaves the nucleus thru nuclear pores
- eacch human chromosome is a long strand of DNA used to make approx 1000 diff seq of RNA
*RNA much smaller than DNA, onyl seg of DNA strand is sued as a template
what is the first step of transcription
rna pol binds to DNA at promoter region
- in humans usually TATA box
how does RNA polymerase do its job
binds to DNA mol and initiates transctipion
- RNA pol surrounds the DNA mol after its been opened and recruits and adds in the complementary RNA nucelotides based on the DNA seq
what occurs once trancription is complete
mRNA undergoes post transcriptional modifcations
- introns are spliced out by spliceosomes while exons stay in
- gets guanine cap and poly A tail to protect it in cytoplasm
what is translation
- prcoess through which mRNA codons are translated into a seq of amino acids
0 ocurs in cytoplasm and involes tRNA, ribosomes, mRNA, amino acids, enzymes and other prot
- divided into initiation, elongation, translocation and termination
describe initiation
ribosome binds to mRNA near its 5’ end
- ribosome scans the mRNA until binds to start codom AUG
- initiator aminoacyl tRNA complex (methionine tRNA) base pairs with start codon
describe elongation
hydrogen bonds forms between mRNA codon in A site of the ribosome and its complementary anticodon on the incoming aminoacyl tRNA compelx
- peptide bond if formed between the amino acid in attached to tRNA in the A site and that in the Psite
- after bond is formed a ribsome carries uncharged rTNA in the P site to the A site
describe translocation
- ribosome advances 3 nucleotides along mRNA
- the uncharged tRNA from P site is expelled and the peptidyl tRNA in A site moves to P site
- aminoacyl-tRNA of next codon can now enter the empty A site
describe termination
occurs when it encounters stop codon UAA UAG or UGA
what is a polyribosome
frequently numerous ribosomes simultaneously translate a single mRNA molecule forming a structure called polyribosome
what occurs after the release of the protein form the ribosome
- assumes its characteristic #D conformation
- this is determined by the primary sequence of amino acids
- additional secondary and tertiary structural folding occurs based on primary seq
- the polypeptide chains can form intramolecular and intermolecular cross bridges with disulfide bonds
describe the structure of the ribosome
large and small subunits that are only associated during protein synrthesis
- has A P and E sites
- A site = aminoacyl tRNA complex binding site, it binds to the enxt incoming tRNA complex
- the tRNA complex is then
NOTE: humans and bacteria have diff subunits that make up the ribosome
- take advantage of this when designing antibiotics that starget the structural diff in bacterial ribosomes leaving human ones un harmed
