2.3 nucleotides Flashcards
What does Adenine pair with?
Thymine / Uracil
What does guanine pair with?
cytosine
What bond does C + G bases have ?
triple hydrogen bond
What bond does A + T bases have?
double hydrogen bond
What bond joins the sugar and bases together
glycosidic bond
3 theories of DNA replication
- conservative (kept the same strand)
- semi-conservative (new strand with old strand)
- dispersive (cut up DNA strands randomly put back together)
What type of bases are adenine and guanine
purine (2 ring structure)
What type of bases are uracil, cytosine and thymine
pyrimidine (1 ring structure)
What is the condensation reaction between the two nucleotides
phosphodiester bond
What is the DNA enzyme polymerase responsible for ?
- joining free nucleotides to the 2 exposed template strand by complementary base pairing
- catalyses condensation reactions of the formation of a phosphodiester bond between the deoxyribose and phosphate group - creating a new backbone of a strand
What is the DNA enzyme helicase responsible for?
- breaking the hyrodgen bonds between the bases
- unwinding and unzipping the DNA
What is the DNA enzyme ligase responsible for?
- joining okazaki fragments together
What is a DNA molecule made up of?
- two polynucleotide strands that run anti-parallel to each other (one is 3’ to 5’ and the other is 5’ to 3’)
How does DNA replicate
semi-conservatively
When does DNA replication occur during the cell cycle
S phase (interphase)
What are the types of mutation
- deletion
- substitution
- insertion
Where does transcription occur
in the nucleus of a cell
Where does translation occur
in the cytoplasm of a cell
What happens during transcription
- helicase unzips the DNA
- one strand acts as the template strand and a complimentary single strand of mRNA pairs up via hydrogen bonds on the template strand
- this should be a copy of the coding strand but thymine is uracil
- once transcribed the mRNA leaves the nucleus via the nuclear pore and the double helix re-forms
What happens during translation
- the mRNA attaches itself to a ribosome
- free molecules of tRNA in the cytoplasm bind to a specific amino acid at their anticodon site
- tRNA moves to the mRNA where only two codons can fit into a ribosome at once
- an activated tRNA molecule with the correct anticodon binds to the codon
- a second specific tRNA molecule binds to the mRNA codon and a peptide bond forms between the amino acids
- the first amino acid detaches from the tRNA and leaves the ribosome (becomes deactivated and collects a new amino acid)
- the process continues until a stop codon is reached
- forms a primary structur of a protein
Which direction does the mRNA molecule grow
5’ to 3’ so binds to the 3’ to 5’ strand (template strand)
Why DNA code degenerate?
- only 20 amino acids but 64 codons
- many codons that can attach to one amino acid
Why is DNA code non-overlapping
- code is read in codons ie 1,2,3 then 4,5,6
Define semi-conservative replication
- replication is increasing the number of DNA strands
- semi-conservative means a new daughter molecule strand is created and an existing parent strand is conserved
What is the importance of semi-conservative replication in the production of new cells
to make genetically identical daughter strands to have the same function
In Meselson and Stahl’s experiment at generation 2 what should test tube show for semi-conservative replication
a band at the top of lighter nitrgoen and a band in the middle of both
