Monohybrid Crosses

Monohybrid Crosses Joohee Kim IB Biology Sec. III

Definition • Tracking inheritance pattern of a single trait between 2 individual organisms

Mendel • Discovered basic rules of inheritance • Analyzed offspring of pea mating

Punnett Square • Tt x Tt = genotype • Tt x Tt = gametes Male gametes T t T t Female gametes • Mandelian ratios: Genotypic- 1TT:2Tt:1tt • Phenotypic- 3 dominant: 1 recessive

Patterns of Inheritance • DNA is passed on to the next generation • In sexual species, the DNA will be a mix of both parents. • There are ways to predict how this new DNA will behave and be expressed • - Genotype and Phenotype

Transmission Genetics • Gregor Mendel in the 1860s • Botanical Crosses • Monohybrid Crosses • Mendel’s Principles of Inheritance

Solving a Genetics Problem • Trait - dominant = A (AA or Aa) • Trait – recessive = a (aa) • _____ x _____ • Punnett Square • Answer questions based on results from Punnet Square ___ ___ ___ ___

Monohybrid Crosses • Cross that involves one pair of contrasting traits • Solve using Punnett Square • Sample problems: • - Rr x rr • - RR x rr • - Rr x Rr • - Rr x RR

Problem • Short hair (L) is dominant to long hair (l) in mice. What is the genotype and phenotype ratio of a heterozygous short-haired mouse crossed with a long-haired mouse?

Solution • Short hair = dominant = L (LL or Ll) • Long hair = recessive l • Ll x II (heterozygote parent = Ll) • Punnett Square: • Genotype ratio: ½ Ll: ½ ll • Phenotype ratio: ½ short hair: ½ long hair

Link for Video • http://www.zerobio.com/videos/monohybrid.html

Monohybrid Crosses