DNA Flashcards
Heterochromatin
Solenoid fibre, tightly packaged DNA = GENES NOT EXPRESSED
Euchromatin
Beads on a string = GENES EXPRESSED
What is the difference between a nucleotide and nucleoside?
Both have sugar + base
Nucleotide has phosphate (DNA)
What is a purine?
2 rings
Adenine (A)
Guanine (G)
What is a pyrimidine?
1 ring
Cytosine (C)
Thymine (T)
Uracil (U) = in RNA
How many H-bonds in the G-C basepair?
3
How many H-bonds in the A-T or A-U basepair?
2
What enzymes are needed in the 3 stages of DNA replication?
Initiation = DNA polymerase (extend 3’ to 5’)+ primates (extend 5’ to 3’)
Elongation = helicase, lagging strand + Okazaki fragments
Termination = DNA ligase
What is senescence?
Permanent cell cycle arrest
Define homozygous
2 alleles of a gene are same
Define heterozygous
2 alleles of a gene are different
Define hemizygous
Only 1 alleles of a gene on X chromosome
What is the start codon in transcription?
AUG = Met
What are the stop codons in transcription?
UAA, UAG, UGA
What is the wobble position in translation?
A single tRNA anticodon can recognise multiple mRNA codons
What is a mutation?
Change of the nucleotide sequence
What is a missense mutation?
Change AA, polypeptide or RNA
What is a nonsense mutation?
Change polypeptide length (frameshift = insertion/deletion)
What is a synonymous/silent mutation?
Change to 3rd base = no effect
What is polyploidy?
Gain haploid set of chromosomes, 3n = 69
What is aneupoloidy?
Loss or gain of whole chromosome due to non-disjunction in meiosis
Trisomies = Down syndrome, 47 + 21
Monosomies = Turner syndrome, 45 X