DNA Structure Flashcards
Polymers: Proteins
Nucleic Acid
Monomers?
Amino Acid
Nucleotide
3 components of DNA:
Sugar (5 C’s)
Bases (N-rich)
Phosphate
Linked with which bond?
Phosphodiester Bond
5’ means what?
5 Prime end of DNA
Name pyrimidines:
Cytosine
Thymine
Uracil
Name Purines
Adenine
Guanine
A forms which bond with T
Hydrogen bond
1000 base pairs =
1,000,000 base pairs =
Kilobase (kb)
Megabase (Mb)
All genetic material in a cell is called it’s
Genome
Prokaryotic genomes (bacterial): Genome with no nucleus in called... Small circles of DNA called... Diploid or haploid? shape of chromosome
Nucleoid
Plasmids
Haploid
Typically circular
Eukaryotics genomes:
Diploid or haploid
Mostly Diploid
Position of constriction on chromosome is called
Centromere
End of chromosome called
Telomere
DNA functions (2)
DNA replication
Gene expression
Repliction of DNA happens when?
before cell division, in interphase
How many daughter cells produced in:
Mitosis
Meisois
2 (2n)
4 (n)
Semi-conservative means:
half old and half new
Which enzyme synthesises leading strand continuously
DNA polymerase
What does RNA polymerase do?
synthesis short RNA primer, which is extended by DNA polymerase
DNA polymerase digests ….. and replaces it with
RNA primer
DNA
What does DNA ligase do?
joins together discontinuous fragments on lagging strand
DNA polymerase can only work when
a nucleotide is present with a free reactive tail (3’)
polymerisation means
joining together of nucleotides
which direction does DNA polymerase polymerise?
5’ to 3’
What is a gene?
Segment of DNA molecule nucleotide sequence producing a product
2 key stages of gene expression:
Transciption
Translation
Transcription=
Translation=
synthesis of an RNA copy of a gene
Synthesis of polypeptide by decoding genetic message within RNA copy
Translation happens where in eukaryotic cell
cytoplasm
Translation cant start until what is made
mRNA
Transfer RNA size and function
Small, transports amino acids to site of protein synthesis
Ribosomal RNA size and function
variable, combines with proteins to form ribosomes
Messenger RNA size and function
Variable, directs amino acid sequence of proteins
Promoters are where sites of what
where transcription starts, DNA sequences that bind RNA polymerase, each gene has own promoter
What hapens at terminator site?
where transcription stops, RNA polymerase leaves DNA
Non-coding DNA is called
Introns
Coding DNA is called
exons
RNA processing 3 steps:
Splicing
Capping
Tailing
RNA processing step order and meaning of each step:
Splicing- introns removed, exons spliced together
capping- cap structure added to 5’ end
Tailing- String of A bases added 3’ end
Ribosome:
protein-making gactory that reads mRNA message and carries out the messages instructions, made up of rRNA & ribosomal proteins
The genetic code:
Message carried by mRNA
tRNA function:
Carrier molecules of amino acids to ribosome
tRNA structure:
Single strand of RNA
secondary structure is cloverleaf structure
consists of base paired ‘stems’ & unpaired ‘loops’
At 3’ end is attatchment point for amino acid
3 bases (anticodon) base pair with mRNA (codon)
3 stages of translation:
Initiation
Elongation
Termination
Stages of initiation (1st stage of translation)
Ribosome recognises & attaches to mRna,
Ribosome translocates along mRNA looking for start codon,
initiator tRNA carries methionine and binds at P site, anitcodon arms match up with complementary sequence on codon of mRNA,
Another tRNA enters at A site and peptide bond formed between 2 bound tRNA amino acids.
Elongation (2nd stage of translation)
ribosome translocates along one codon along mRNA
uncharged tRNA leaves rivosome via exit E
ribosomes receive charged tRNA dictated by each codon
ribosome continues to translocate along mRNA 5’ to 3’
Termination (3rd stage of translation)
Ribosome continues along mRNA till stop codon
no tRNA enters stop site
Release factor proteins enters instead resulting in translation termination
translation complex dissociates
polypeptid is released and folded to become mature protein.
