lecture 2

what is genetics?

the study of inherited traits

what is a genome?

the genetic blueprint

what is the central idea of genetics?

genes

what are monohybrid crosses?

the cross fertilization of 2 true breeding parents for each trait

• monohybrid crosses (one trait)

common F1 observation

no inherited traits, all dominant traits and no recessive

common F2 observation

the recessive phenotype returned in a small quantity and the dominant was still showing

what is the output of a monohybrid cross after 2 generations (P0 →F1→ F2)

3:1 genotype

dominant : recessive

common F3 observation

1:2:1 genotype

dominant : mix : recessive

homozygous alleles

AA or aa

heterozygous alleles

Aa

what always shows its phenotype

the dominant allele

what is mendel’s first law?

law of segregation

what is the law of segregation

2 copies of each gene randomly segregate into the gametes which only have one copy

what is the genotype and phenotype in the F2 generation of a RR x rr

P0 → RR x rr

F1 → Rr

F2 → RR : 2 Rr : rr

• genotype is 1:2:1

• phenotype is 3:1

what is the testcross?

crossing a strain with the dominant phenotype (unknown genotype) with a conrtol strain that is homozygous for the recessive allele

• so dominant has to be either SS or Ss

• if SS, all are Ss

• if Ss, half are Ss and half are ss

what are dihybrid crosses?

the crossing of 2 traits

• SS YY x ss yy

if the cross is SS YY x ss yy, what is the first generation?

Ss Yy