DNA & Chromosomes Flashcards
deoxyribonucleic acid
DNA
Raw material of inheritance and ultimately influences all aspect of the structure and functioning of the human body.
DNA Molecule
single molecule of DNA and associated
proteins.
Chromosome
located in the nuclei and each human cell contains about 23 different pairs of chromosomes.
Chromosome
Composed of repeating units of “nucleotides” which consist of: (3)
Deoxyribose sugar
Phosphate group
One of 4 nitrogen containing bases
2 Bases
Purines
Pyrimidines
Adenine and Guanine
[bases]
Purines
Cytosine and Thymine
[bases]
Pyrimidines
backbone - found in the outer structure of the helix.
Sugar and phosphate groups
positioned side by side n the inside of the double helix.
Nitrogenous base
DNA Synthesis [steps]
- Initiation
- Replication
- Termination
Breakage of hydrogen bonds mediated by DNA Helicase and single stranded binding protein (SSB).
[dna synthesis steps]
Initiation
Primase generates an RNA primer which initiates replication by binding the DNA Polymerase takes place in both strands but nucleotide can only be added to the 3’ end of an existing strand (leading strand).
[dna synthesis steps]
Replication
The 3’ end which consists of non - coding DNA (telomere) is cut off. Enzymes proof-read the sequence (correct pairing) and enzymes called nuclease remove incorrect DNA.
[dna synthesis steps]
Termination
Enzymes proof-read the sequence (correct pairing) and enzymes called?
nuclease remove incorrect DNA
The nitrogenous bases of DNA are not present in equal proportions and that the proportions of these bases vary from one species to another.
Chargaff’s Rule
Consist of a single continuous molecule of DNA complexed with histones and non histone proteins.
Chromatin
4 Several levels of DNA organization
- DNA Helix
- Histones
- Solenoid
- Chromosome
Consists of 2 sister chromatids each of which is comprised of contracted and compacted double helix of DNA.
Chromosome Structure
more condensed
[chromosome parts]
Heterochromatin
silence genes (methylated)
[chromosome parts]
Heterochromatin
gene poor (high at content)
[chromosome parts]
Heterochromatin