GENETICS - Basics Flashcards
What is the process of DNA replication (4)
- DNA helix (parent strand) unwound by DNA helicase to form two single strands (templates)
at the replication fork - DNA polymerase adds nucelotides to these templates to allow new DNA leading strand to grow in 5’ to 3’ direction
- DNA lagging strand formed by discontinuous short nucleotide strands called Okazaki fragments by a different DNA polymerase which is formed in the 3’ to 5’ direction
- Thees are joined together by DNA ligase
What is transcription? What enzyme is involved?
DNA code is read in nucleus and complementary messenger RNA is produced, which leaves for the cytoplasm for protein synthesis.
RNA polymerase in a 5 prime to 3 prime direction
What is the structure of mitochondrial DNA? What type of inheritance? Which genes does it code for?
- Circular double stranded-DNA
- Inherited from mother
- Encodes 37 genes that produce structural RNA (22 tRNA, 2rRNA) & Proteins of electron transport chain (complex I, III, IV and V)
What is the relation between histones and DNA?
histones are alkaline positively charged proteins, allow them to interact with negatively charged DNA
Which is the short arm chromosome and which is the long arm chromosome?
p - petit
q - long
What is the structure of a nucleotide (3)
- Deoxyribose (pentose sugar)
- Nitrogen base (purines and pyramidines)
- Phosphate Group
How are adjacent nucleotides linked to each other?
How are the DNA strands linked to each other?
- 3’ to 5’ phosphodiesterase bond
- Hydrogen bonds between bases.
DNA complexes are called?
Histones
Histones packed together to make chromatin.
Chromatin fibre pack together to form a chromosome.
Whats the difference between euchromatin and heterochromatin? (2)
- Euchromatin is less densely packed than heterochromatin
- Euchromatin contains acetyl group
How long does a cell cycle last?
Usually 24 hours
What is the G0 stage?
Cell is quiescient, some cells permanently stopped in G0
What is the M stage?
Mitosis - occupies one hour
What happens in G1 stage?
Biosynthetic activity, cellular contents are duplicated (excluding chromosomes)
What happens in S phase?
DNA synthesis and chromosomal replication to form two daughter chromatids (6-8 hours)
What happens in G2 stage?
Second gap phase with preparation for division (cell doubles mass, chromosome checks for errors)