5.1 mendelian inheritance pages 184-193. trait a particular version of a characteristic that can be...
TRANSCRIPT
Monohybrid crosses
breeding two organisms with different versions of only one traitP generation (parental) …true breedingF1 generation (filial generation)…hybrid offspring
F2 generation
Crossing the F1 generation: F2 generation with some purple and some white, but no pink flowers.3:1 ratio of purple to white flowers
Mendel’s conclusions
1. For each trait, an organism carries two genes, one from each parent.
2. Parents donate only one copy of the gene to their offspring. (sperm and eggs are haploid)
Genotype vs. Phenotype
Genotype: the organism’s genes (genetic make-up) including genes that are hidden from view
Phenotype: the traits that are expressed, the physical appearance of the organism.
Dominant vs. Recessive Alleles
A Dominant Allele is expressed if it is present in the gene. Ex. PP, Pp, pP
A Recessive Allele is expressed only if there is no dominant gene Ex. pp
Purple vs. White flowers
• Let P be the purple flower gene• Let p be the white flower gene• Homozygous…both alleles are the
same, PP or pp• Heterozygous…both alleles are
different, Pp
What you see …isn’t always what you get!
Genotype PhenotypePP homozygous dominant
purple
Pp heterozygous Purple (carrier of white gene)
pp homozygous recessive
white
Probability
The measure of the chance that an event will happen.Example: Toss a coin, call it.The chance of tails is 50%
Test Crosses
To determine if the parent is PP or Pp, cross it with a homozygous recessive individual.
If 100% of the offspring show the dominant trait the parent was PP.
If the offspring displays both phenotypes, the parent was Pp.
Green pods vs. yellow pods
Y…yellow (dominant)y…green (recessive)Cross between yellow heterozygous and green homozygous recessive