mendelian genetics - lecture 11 Flashcards
Who is Gregor Mendel?
- mid 19th century
- Experiments done in 1856- 1863
- these experiments were published in 1866
What were Mendels laws of inheritance?
- law of segregation
- law of independent assortment
- principle of dominance
What is Mendels model organism ?
Pisum sativum
Why is pisum sativum a model organism?
- Easy to cultivate
- Many progeny
- one generation growing season
- many pure breeding varieties
- 7 discontinuous traits
Who is Edith Rebecca Saunders?
- re-discovered some of Mendels work
- defined the terms “allelomorphs” , heterozygote and homozygote
What are the 4 monohybrid conclusions that can be drawn ?
1 - one character is encoded by two genetic factors
2- two genetic factors (alleles) separate when gametes are formed
3 - the concept of dominant and recessive traits
4- two alleles separate with equal probability int the gametes
What happens in a simple mendelian cross?
p = parental
F1 = 1st filial
F2 =2nd filial . Ends up with a classic “Mendelian” 3:1 ratio
What are Mendels conclusions (4 of them)
a) inheritance is not blending
b) inheritance is “particulate”
c) F1 still has information for both phenotypes coz seen in F2s?
d) alleles segregate 50:50
What is an explanation of the law of segregation?
The two alleles segregate when gametes are formed, and one allele goes into each gamete.
what is an explanation of the principle of dominance?
sometimes only the trait encoded by one of them - the dominant allele is observed in the phenotype
Testing for Mendelian ratios ?
- Do a chi - squared test
- testing for deviation away from 3:1
What is a pedigree analysis in humans?
- no crosses involved, Expected pattern in pedigree depends on dominance
What is a reciprocal cross?
Pair of crosses with phenotype of male and female parents reversed.
e.g Tall mum x short dad … short mum x tall dad
What is gene linkage?
Genes that are close together on the same chromosome usually segregate as a unit
What is independent assortment?
formation of random combinations of chromosomes in meiosis and of genes on different pairs of homologous chromosomes
