Chromosomes, Genes and DNA Flashcards
What is heterochromatin?
Chromatin which is packed tightly and is not being read.
What is the beads on a string model?
DNA is wound around histone cores, in an arrangement that looks like beads on a string.
What is the difference between a major and minor groove of DNA? Why do these arise?
DNA is a flexible molecule, no due to the nature of the helix there are two different grooves. Minor grooves are the flexible grooves. These arise due to the asymmetrical nature of the molecules.
What is a nucelosome?
It is a histone core with its DNA wound around it.
The beads on a string in DNA are tightly packed into another structure. What is this called?
Solenoid.
How do solenoids form chromosomes?
Solenoids form loops and are tightly packed into chromosomes. In chromosomes, DNA cannot be read.
What is the difference between a nucleotide and a nucleoside?
A nucleoside contains a base and a sugar. An nucleotide contains both of these and a phosphate molecule.
What is the difference between RNA and DNA (in terms of the molecules they are composed from)?
DNA is composed from deoxyribose sugars. These only have one OH group. RNA is composed of ribose sugars which each have 2 OH groups.
What is the difference between a purine and a pyrimidine?
Purines have a double ringed aromatic structure whilst pyrimidine only have a single ringed structure.
Which sugars are purines?
Adenine, guanine.
Is cytosine a purine or a pyrimidine?
Pyrimidine
Is thymine a purine or a pyrimidine?
Pyrimidine
Is adenine a purine or a pyrimidine?
Purine.
What is uracil?
Uracil is a pyrimidine which is only found in RNA not DNA instead of thymine.
RNA/DNA are polymers. What kind of bond connects each individual subunit?
Phosphodiester bond.
How do DNA bases pair and how many hydrogen bonds do they form?
Guanine pairs with cytosine with 3 hydrogen bonds.
Adenine pairs with Thymine with 2 hydrogen bonds.
What is an RNA stem loop?
This is where there are 2 anti parallel RNA sequences on the same molecule and they come together due to their complementary nature and form a loop.
What is the conventional direction for writing DNA sequences?
5 prime to 3 prime.
What is meant by DNA replication being a semi conservative method?
This means that one strand is maintained and used as a template.