Different Genetic Outcomes and Human Genetics

1. Different Genetic Outcomes and Human Genetics Chapters 11.3 and 14.1

2. Mendel’s experiments further • In his first experiment Mendel showed that the alleles for a trait segregated independently • Now he wondered if alleles for different traits were linked • He conducted a dihybrid cross  two traits • Crossed a true-breeding yellow round seed plant (RRYY) with a true-breeding green wrinkled seed plant (rryy) • F1 generation was 100% yellow and round • You can see this result with a 16 box punnett square • He then crossed the F1 offspring • 9 yellow round • 3 yellow wrinkled • 3 green round • 1 green wrinkled • This led to Mendel’s principle of independent assortment • Genes for traits segregate independently from each other during the formation of gametes in meiosis • This accounts for the wide variety of genetic variation in organisms

4. Exceptions to Mendel’s principles • Incomplete dominance  When one allele is not completely dominant over another • Crossing a red flower and a white flower and the offspring are pink • Codominance two genes are dominant and show • Cross a black chicken with a white chicken and the offspring are black and white • Blood types in humans • A and B are dominant, O is recessive

6. Human Genetics • Karyotype a picture of all the chromosomes • Can be used to diagnose genetic disorders • Humans have 46 chromosomes or 23 pairs • The first 22 pairs are called autosomes, the last pair are the sex chromosomes • Females have two X chromosomes • Males have an X and a Y

7. Pedigrees  a tool used to show relationships within a family • Genetic counselors analyze pedigrees to determine possible genotypes of family members • Can be used to predict genetic diseases • Genes and environment  a phenotype is only partially determined by genes, the environment plays a role as well • Ex: height is genetically determined but can be affected by poor nutrition