DNA Flashcards
what are codons
a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis
what are anticodons
a sequence of three nucleotides in transfer RNA that binds to a corresponding codon and designates a specific amino acid.
nucleotides
a group of biological molecules that contain carbon, hydrogen, oxygen, nitrogen & phosphate.
what are the 2 types of nitrigenous bases that nucleotides contain?
- purines
- pyrimidines
what nitrogenous bases do purines contain?
- adenine
- guanine
what nitrogenous bases do pyrimidines contain?
- thymine
- cytosine
- uracil
what is ATP?
- an energy transferring molecule (not a storage molecule)
- called the “universal energy currancy” because its a universal energy source used in all living organisms
how is ATP formed?
formed in an endergonic (energy-requiring) reaction
where does the energy required to make ADP come from?
cell respiration
exergonic reaction
releases energy
endergonic reaction
absorbs energy
why is ADP useful as an energy source for biological reactions?
- atp hydrolisis releases energy in small, managable amounts
- lots of energy would be wasted as hear, causing organism to overheat- enzymes would denature
what are formed when nucleotides are joined together?
nucleic acids
DNA function
to hold genetic information
RNA function
transfers genetic information from DNA to the ribosomes- process of protein synthesis.
how is the amino acid sequence determined
by the sequence of bases (a gene) in DNA
what are the complimentary base pairings
- thymine/uracil & adenine
- cytocine & Guanine
purine bases
have 2 rings
pyrimidine bases
have one ring
what is a single polynucleotide chain known as
a dna strand
list the features of a DNA molecule + function
- sugar-phosphate backbone protects the bases
- hydrogen bonds between the pairs of complimentary bases to hold the 2 strands together
- the hydrogen bonds are individually weak but collectively strong
rRNA
- ribosomal RNA
- structural component of RNA
- important for protein synthesis
what base replaces thymine in an RNA molecule
uracil
what is the purpose of the extra oxygen in the ribose
stops the RNA from forming a double helix
what are 3 types of RNA
- mRNA (messanger RNA)
- rRNA (ribosomal RNA)
- tRNA (transfer RNA)
mRNA
- messanger RNA
- complimentary copy of the section of DNA which codes for 1 polypeptide
- carries the code from the nucleus to the site of protein synthesis (ribosome)
tRNA
- transfer RNA
- carries a specific amino acid to the ribosome where amino acids are joined by peptide bonds to form a polypeptide
- tends to fold up by complimentary base pairing
list the steps of DNA replication
- DNA helicase breaks the hydrogen bonds between bases- this unwinds the DNA & exposes the unpaired bases on the templae strand.
- free nucleotides from nucleoplasm are attracted to their complimentary base pairs on each seperated strand
- DNA polymerase forms phosphodiester bonds between nucleotides
- 2 identical DNA molecules are formed
what does DNA code for?
proteins
where are instructions to make proteins found
in our DNA
what is transcription and where does it occur?
- occurs in the nucleus
- where DNA is used as a template to make mRNA (messanger)
what is translation and where does it occur
- occurs in the cytoplasm
- the information contained in the mRNA is used to make polypeptide
list the process of transcription
- DNA helicase enters the portion of DNA molecule, in the region of gene to be transcribed
- DNA helicase breaks the hydrogen bonds & unwinds the DNA, exposing the bases on both strands of the DNA in the region of the gene
what is a template strand
one strand acts as a template strand to construct mRNA molecule
what is RNA polymerase?
links to the template strand & inserts mRNA nucleotides 1 at a time (joins them)
what is a stop sequence?
- ends the mRNA, RNA polymerase leaves
- DNA recoils back into its original shape
what happens to the DNA after the RNA polymerase leaves
- DNA needs to be translated into a protein
- messenger RNA leaves and finds a ribosome
where does messenger RNA go after transcription
to find a ribosome
what are the 3 processes of translation?
- initiation
- elongation
- termiationn
gene
starting point for protein synthesis
summarise the steps of translation at a ribosome
- each tRNA molecule carries specific amino acid
- the ribosome binds to the start codon on the mRNA
- tRNA molecules bind to the ribosome through codon- anticodon interaction
- a peptide bondis formed between the amino acids
- the ribosome moves along the mRNA one codin at a time
- this continues until a stop codon is reached.
‘one gene one protein hypothesis’
- genes are linear sequences of nucleotides
- this sequence is divided into triplets
- they are non-overlapping
- they are unambiguous
- they are degenerate
unambiguous (one gene one protein hypothesis)
each codon specifies to one amino acid only
degenerate (one gene one protein hypothesis)
several different codes can code for the same amino acid
