DNA structure and replciation Flashcards
Why is DNA important
- DNS encodes for genes
- Molecular basis for inheritance
- Contains the code for all other cellular molecules
- Complimentary structure allows it to be replicated and the code to be read
- Variations in DNA sequence lead to phenotypic differences and susceptibility to disease
- Defects in DNA replication and repair lead to many diseases
what is a nucleotide made out of
- made out of a nitrogenous base, a pentose sugar called deoxyribose and a phosphate group
what do nucleotides join together to make
they join together to make a DNA strand
what happens when DNA wraps around histone proteins
they form nucleosomes
what do nucleosomes form during compaction
chromatins
describe the structure of the DNA
- They have an antiparallel strand which means they go in opposite directions, one goes 5 to 3 and the other goes 3 to 5 direction
- There are two groups purine and pyrimidine - The nucleotides are joint by phosphodiester bonds between the phosphate group of one nucleotide and the carbon on another nucleotide
- GC are held together more tightly due to 3 hydrogen bonds, this affects structure and function of the chromosome
- No bonds between adjacent nucleotides other than the sugar phosphate backbone
what are the purine bases
adenine and guanine
what are the pyrimidine bases
thymine and cytosine
how many rings does purine have versus how many rings does pyrimidine have
purine has two nitrogenous bases whereas pyrimidine has 1 nitrogenous base
how many hydrogen bonds join A and T
2
how many hydrogen bonds join C and G
3
whats the difference between 5 prime and 3 prime ends
- In the 5 direction there is a free phosphate group on the sugar backbone whereas in the 3 position there is an unlinked OH group on the sugar backbone
what is the central dogma
- DNA sequence is the template for RNA
- DNA is transcribed and it becomes RNA and forms base triplets
- Base triplets join to amino acids during translation and forms a protein
what does each cell have
2 metres of DNA
what are the core proteins that make up the histone that the nucleosome wraps around
- made up of 8 histone molecules these are called core histone proteins
- 2x H2A
2x H2B
2x H3
2x H4
and there is only one linear histone called H1
describe the compaction of nucleotides into the nucleosomes and nucleosomal fibre
- DNA wraps around a histone twice, to give the nucleosomal fibre
- DNA between the two nucleosomes is called linker DNA