DNA Flashcards
DNA
Two antiparallel strands of DNA (adenine, thymine, guanine cytosine base pairs)
Found in nucleus, same sequence in every nucleus
5’ - G T C A - 3’
3’ - C A G T - 5’
Human Genome
3.2 billion nucleotide pairs
Two copies in every cell (except germ cells)
One from mother, one from father
Chromosomes
23 pairs - 1 pair for sex
p (smallest) arm and q (largest) arm from the centromere (starts at 11)
Locations along chromosomes identified with G-stain banding
Mitosis
Cell division of diploid cell, leads to two identical cells with two sets of chromosomes (diploid cells)
Meiosis
Diploid germ cell creates four haploid gamete cells (sperm/egg)
Cross-overs (recombinations) happen in meiosis leading to hereditary diversity. Variation of 3-fold in number of crossovers
Mutation
Alteration in nucleotide sequence of the genome of an organism Single point More significant (transposons, chromosome cross over)
Mutation causes
DNA copying mistakes occur in replication
Exposure to environmental mutagens (radition/chemicals)
Infection by retroviruses (integration into the host cell genome)
Types of mutation
Point mutations
Frameshift mutations
Chromosomal alterations
Point mutations
Change a single nucleotide
Frameshift mutations
Insertions/deletions of nucleotides
Chromosomal alterations
Deletion
Duplication
Inversion
Reciprocal Translation
Transposon
Transposable element/jumping genes
Change position within the genome, usually during replication
Creates or reverses mutations
Often result in duplication of genetic material
Repeat sequences on each side of transposon
Very few active transposons
Germline mutation
Mutation is already present or occurs in the germ cells
Entire organism carries the mutation (half of gametes)
Somatic mutation
Mutation occurs during the life of the individual
Only occurs in patch of affected area (None of the gametes carry the mutation)
Haemophilia
Sex-linked X chromosome disorder
Manifests in males
Recessive in females
Germline mutation
