Inheritance: Mendelian Genetics I. Gregor Mendel (1865) A. Before Mendel B. Mendel’s experimental approach II. Genetic terms 1. genes 2. gene pair 3. alleles 4. homozygous/heterozygous 5. dominant/recessive 6. homozygous dominant and recessive/heterozygous 7. genotype/phenotype III. Genetic crosses A. Monohybrid crosses B. Dihybrid crosses IV. Mendel's discoveries A. Principle of segregation B. Principle of independent assortment C. Genes are particles
A. Before Mendel The blending theory (paradigm) Inheritance of acquired characteristics
Red coat in foxes is a dominant trait; white is the recessive trait. If a red fox whose mother had a white coat is bred to a white fox, what will be the probable percentage of red kits (baby foxes)? a. 25% b. 50% c. 75% d. 100%
If two achondroplasic dwarfs have children, what fraction of the children would be expected to be dwarfs like their parents? a. 1/4 b. 1/2 c. 2/3 d. 3/4
What determines how common a trait is in a population?
B. Dihybrid crosses: Human traits Dimples dominant to no dimples Brown eyes dominant to blue Dark hair dominant to light hair Curly hair incompletely dominant to straight hair
In humans, a widow's peak is dominant and a straight hairline is recessive. Dimples are dominant and no dimples are recessive. A male who is heterozygous for both widow's peak and dimples has a child with a woman who has a straight hairline and no dimples. What is the phenotype ratio of children can they produce? a. 3: 1 b. 2:2 c. 1:1:1:1 d. 4:0
IV. Mendel’s discoveries A. Principle of segregation Sexually reproducing diploid organisms have 2 alleles of each gene. These 2 alleles segregate from each other to form gametes that contain only 1 allele of each gene.
B. Principle of independent assortment Different genes on different chromosomes segregate into gametes independently of each other.