Monohybrid Crosses Joohee Kim IB Biology Sec III

Monohybrid Crosses Joohee Kim IB Biology Sec. III

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

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

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

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

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

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

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

Problem n 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 longhaired mouse?

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

Link for Video n http: //www. zerobio. com/videos/monoh ybrid. html