1. Punnett Square Notes Chapter 11-2 Mrs. Kooiman La Serna High School

2. Review Vocabulary A haploid sex cell (sperm or egg) with only ONE set of chromosomes. Gamete: A haploid sex cell (sperm or egg) with only ONE set of chromosomes. The “types” of genes a person has. Example…TT, Tt, tt Genotype: The “types” of genes a person has. Example…TT, Tt, tt The physical characteristics of a person. Example…tall or short. Phenotype: The physical characteristics of a person. Example…tall or short. The stronger allele Dominant: The stronger allele The weaker allele Recessive: The weaker allele Two of the same alleles (TT, tt) Homozygous: Two of the same alleles (TT, tt) : Two different alleles (Tt) Heterozygous: Two different alleles (Tt)

3. Punnett Square A diagram that predicts the expected outcome of a genetic cross by considering all combinations of gametes in the cross. A diagram that predicts the expected outcome of a genetic cross by considering all combinations of gametes in the cross. MONOHYBRID CROSS Involves ONE PAIR of contrasting traits Involves ONE PAIR of contrasting traits

4. Example #1: Yellow color in seeds is dominant over green color in seeds. What letter would represent yellow gametes What letter would represent yellow gametes Y (Upper case, dominant trait) What letter would represent green gametes What letter would represent green gametes y (lower case, recessive trait, use first letter of dominant trait) A plant that is homozygous for yellow seeds () is crossed with a plant that is homozygous for green seeds (). What could their offspring look like? X YY yy YY yy

5. Set up the Punnett Square Write the genotypes of each parent. Put each allele (gene) in it’s own column. Then cross the gametes to determine the possible genotypes of the offspring Write the genotypes of each parent. Put each allele (gene) in it’s own column. Then cross the gametes to determine the possible genotypes of the offspring Y yyyy Parent #1 Parent #2 YyYy YyYy YyYyYyYy

6. Questions How many of their offspring will be yellow? How many of their offspring will be yellow? 4 out of 4 – 100% (the dominant trait is stronger than the recessive trait) How many of their offspring will be green? How many of their offspring will be green?0 Are the offspring homozygous or heterozygous? Are the offspring homozygous or heterozygous?heterozygous

7. Example #2: Two plants that are heterozygous for seed color are crossed, what would their offspring look like? X Parent #1 Parent #2 YyYy YyYy YY Yy yy Yy

8. Questions What percent of the offspring are homozygous dominant? What percent of the offspring are homozygous dominant? 1 out of 4 – 25% What percent of the offspring are heterozygous? What percent of the offspring are heterozygous? 2 out of 4 – 50% What percentage of the offspring are homozygous recessive? What percentage of the offspring are homozygous recessive? 1 out of 4 – 25% How many of offspring will be yellow? How many of offspring will be yellow? 75% How many of the offspring will be green? How many of the offspring will be green? 25%