Nucleic acids Flashcards
(25 cards)
Erwin Chargaff’s theory
Complementary base pairings
For all organisms, G is very close in composition to C and A is closing composition to T
Variation from exact match is due to experimental error or free nucleotides in cell
Meselson & Stahl semiconservative theory
Each strand act as a template for a new strand. Newly synthesised DNA molecules contain one old and new strand.
How can the four bases of DNA allow for the production of so many different proteins?
Triplet code for one amino acid
There are 64 combinations of the four bases
Different base sequences will give rise to different amino acid sequence
Different amino acid sequences leads to a wide variety of different proteins
The function of all four types of nucleic acid
DNA - provides the genetic code for production of all RNAs
rRNA - to form ribosomes/site of translation
mRNA - produced in transcription and used in translation
tRNA - delivery of amino acids to the site of protein synthesis
Where in the cell each nuclear acid carries out its function
DNA - nucleus
rRNA - cytoplasm/rough ER
mRNA - cytoplasm/ribosomes
tRNA - cytoplasm
How does tRNA activation work?
ATP provides energy for reaction
Two phosphate are released
Amino acid reacts with ATP to form activated amino acid
Amino acid is transferred to tRNA forming activated tRNA
Using RNA polymerase describe how the viral RNA is replicated
RNA acts as a template
Three RNA nucleotides attached to their complementary base pairs
Adenine with uracil and cytosine with guanine
RNA polymerase catalyses the formation of the new RNA molecule
Forming the phosphodiester bond
Describe how proteins in the capsid are produced
translation
mRNA attaches to a ribosome
tRNA brings a specific amino acid
Complementary based pairing between mRNA codon and tRNA anticodon
Ribosome has room for two tRNA molecules
Condensation reaction occurs
Ribosome move to the next codeon
Post translation processing
The three parts of the ATP molecule
Phosphate
Ribose
Adenine
Three variables which would need to be controlled during centrifugation of the samples
The temperature of the samples
Time
Volume of DNA
The results of generation zero and one supporting the theory of semiconservative replication
Generation zero is all N 15
Generation one is a mixture of heavy and light
Because each molecule retains one strand of heavy isotope and one strand of the newly formed DNA of light isotope
The different densities of DNA in generation two and generation 3
Only N 14 are available for replication
Generation two has equal peaks because one strand of heavy and one strand of light DNA have been used as templates for the formation of new DNA molecules
Generation three has a higher peak of N 14 because more light DNA strands are used as templates
DNA polymerase
DNA polymerase joins the free nucleotides to the end of the new DNA strand
What is meant by the term universal energy currency?
Source of energy in all living things
When would ADP be transferred to ATP with the help of creatine phosphate
During exercise, ATP can be generated quickly when phosphate group is given to ADP
When would ATP be transferred to ADP with the help of creatine phosphate
At rest creatine phosphate is created to be a store of phosphate
What is the position of cholesterol molecules within the plasma membrane?
Between the fay acids
Why is it necessary that the code is a triplet code?
A triplet code can produce 64 different combinations which is enough to code for 20 amino acids
What does degenerate mean?
Set amino acids are coded for by more than one mRNA codon
What happens when energy is released and energy is stored?
Energy is released when ATP is hydrolysed to ADP and PI
Energy is stored when ADP and phosphate are joined
Universal energy currency
It is the source of energy in all cells in all organisms
Meselson and Stahl division 3
3 lighter isotope
1 mix band
How does a replication fork show semi - conservative replication
It shows that each original strand of DNA acts as a template for a new strand.
New DNA contains one old and one new strand
What is the importance of the proof-reading role to the organism
The base sequence is different
This will leads to different mRNA being produced and a different sequence of amino acids
The protein may be non functional de to changed 3D shape
