BMS2042 Lecture Notes - Lecture 1: Anemia, Thalassemia, Transferase
30 May 2018
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Week 1. Autosomal/Sex linked inheritance &
Extensions to Mendelian I
AUTOSOMAL INHERITANCE
• Model organisms: reproduce quickly, cheap, no ethics, lots of progeny and can be bred in lab
eg. mice, bacteria, insects
• Mendelian inheritance early theories:
Pangenesis
o Genetic information from different parts of the body are transferred into
gametes
o Acquired inheritance
Homunculus
o Small person in head of sperm
Blending theory
o Blend of both parents
o Closest theory
• Mendel discovered autosomal inheritance
o Looked at simple traits of peas (one trait at a single time)
• Crosses:
Monohybrid
crosses
o Only one trait differs
o F2 = 3:1 phenotype ratio
F2 = 1:2:1 genotype ratio
o Hypothesis to explain data: gene and alleles (different versions of gene)
o Medel’s law of segregation (first law)
Test cross
o Cross to homozygous recessive to determine if individual showing
dominant phenotype is homozygous or heterozygous for dominant allele
o Usually for F2
• The P gene for purple pigmentation in flowers is not an enzyme but a transcription factor
• Inheritance pattern for two traits:
o F1 = two dominant phenotypes
o F2 = 9:3:3:1 phenotype ratio
o Two traits assorted independently during production of gametes
find more resources at oneclass.com
find more resources at oneclass.com
o Medel’s law of idepedet assortet seod law
• Mendel’s laws:
1st law: Medel’s law of segregatio
o The two alleles segregate equally (as do members of
a pair of homologous chromosomes) from each
other into the gametes, each gamete has ½ chance
of inheriting each allele. Gametes combine at
random to form next generation
o Confirmed by meiosis
2nd law: Medel’s law of idepedet
assortment
o Each pair of alleles segregates independently (as do
different chromosome pairs) of other alleles during
gamete formation
• Autosomal inheritance in humans:
o Use family data through pedigrees
o Data is usually limited, can only determine the most likely mode of inheritance
Autosomal or sex linked?
Dominant or recessive?
Autosomal recessive
Autosomal dominant
o Males and females equally affected
o Skips generations
o Common for parents to be related
o Eg. cystic fibrosis, albinism, Tay-sachs
disease
o Males and females equally affected
o Affected individuals in multiple generations
o Transmission by both sexes to both sexes
o Eg. achondroplasia, Huntington disease
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Autosomal inheritance: model organisms: reproduce quickly, cheap, no ethics, lots of progeny and can be bred in lab eg. mice, bacteria, insects, mendelian inheritance early theories: Pangenesis: genetic information from different parts of the body are transferred into. Blending theory gametes: acquired inheritance, small person in head of sperm, blend of both parents, closest theory, mendel discovered autosomal inheritance, looked at simple traits of peas (one trait at a single time, crosses: Test cross: only one trait differs, f2 = 3:1 phenotype ratio. Inheritance pattern for two traits: f1 = two dominant phenotypes, f2 = 9:3:3:1 phenotype ratio, two traits assorted independently during production of gametes, me(cid:374)del"s law of i(cid:374)depe(cid:374)de(cid:374)t assort(cid:373)e(cid:374)t (cid:894)se(cid:272)o(cid:374)d law(cid:895, mendel"s laws: 1st law: me(cid:374)del"s law of segregatio(cid:374: the two alleles segregate equally (as do members of a pair of homologous chromosomes) from each other into the gametes, each gamete has chance of inheriting each allele.
