Flashcards in Chromosomes, Genes And DNA Deck (18):
What charge does DNA have?
In an electron micrograph, what appears darker - heterochromatin or euchromatin?
What is the difference between the pentose sugars in DNA and RNA?
RNA - pentose sugar has an OH group
DNA just has an H on its own
What is the difference between a purine and a pyrimidine?
Purine has 2 rings
Pyrimidine has 1 ring
Name the purine bases
Guanine and adenine
Name the pyrimidine bases
Thymine, cytosine and uracil
Which bonds are found between nucleotides?
What is a nucleoside?
A nitrogenous base and a pentose sugar (found in RNA)
What is found at the 5' end and at the 3' end in DNA?
5' - a free phosphate group
3' - an -OH group
Give some key features of the DNA double helix
Strands run anti-parallel
One complete turn is 10 base pairs
Purines and pyrimidines are planar and unsaturated
Space between base pairs is 0.34 nm
Within sugar-phosphate backbone, major and minor grooves exist
In DNA replication, what does helicase do?
It uses ATP to unravel the DNA double helix
Helicases also reform the DNA helix around the replication fork
What occurs in initiation of DNA replication?
Recognition of origin of replication
Helicase unravels the DNA double helix
DNA polymerase is recruited. This can only start from 3' end so PRIMASE is needed to initiate each strand
What occurs during DNA elongation?
Leading strand is replicated from 5' to 3'
Lagging strand is replicated discontinuously as Okazaki fragments
Fragments are joined by DNA ligase from OH to phosphate group
What does DNA ligase do?
Joins Okazaki fragments together
Describe the process of termination in DNA replication
Replication forms move from the ends of the DNA strands towards eachother
Lead strands move towards lagging strands and vice versa
How many bonds are between the base pairs GC?
Describe how DNA is packaged into chromosomes
DNA wrapped around histones to form nucleosomes - beads on a string
These pack tightly together to form solenoid structures
These fibres are compacted into several hierarchical loops
These create chromosomes