Punnett Squares And Meiosis!

Meiosis: A type of cell division in which a diploid cell (two copies of each gene) divides to form a haploid cell (one copy of each gene). = SPERM and EGG!

Dominant T - curved thumb/allele Recessive t - not curved allele Dominant T - curved thumb allele Recessive t - not curved allele Tt T t T t

Punnett Square: A method to determine the likely genotypes and phenotypes of offspring T t T t eggs sperm tt Tt TT Curved thumb Straight thumb Curved thumb

How to fill in a punnett square

Using the Punnett Square below, correctly cross a heterozygous brown haired person with a homozygous blonde haired person. Bb x bb B = brown hair allele b = blonde hair allele B b b b bb Bb bb

b BbBb Bb bb Phenotype: 2 brown hair and 2 blonde hair Genotype: 2 Bb and 2 bb

Solve the following problems: GIVE THE PHENOTYPE & GENOTYPE! Cross EE x ee (brown eyed person with blue eyed) Cross a wrinkled seed with a homozygous round seed (W = wrinkled w = round) Cross a heterozygous tall person with a heterozygous tall person. Cross a homozygous tall person with a short person

Mendel’s Laws

Law of Segregation Two alleles separate from each other during meiosis! Each homologous chromosome pair separates during the formation of the sperm and egg (meiosis!)

Law of Segregation

Law of segregation

Incomplete Dominance Hh (heterozygote) where the functioning allele makes less protein Example: in snapdragon flowers, red is dominant, but less protein pigment is made w/ Rr; the flower is pink (Rr) = pink

Incomplete Dominance Practice In the budgerigars bird (“budgie”), olive feather color is dominant (GG), dark green is heterozygous (Gg), and light green is recessive (gg). Cross an olive bird and a light green bird. Cross two heterozygous birds

Codominance When both alleles (forms of a gene) are expressed Blood type is an example of codominance Blood type A is codominant with B Blood type O is recessive to A and B

Codominance Practice Cross a person with type O blood (oo) with a person who has type A blood (Ao). What are the possible genotypes and phenotypes of their children? G: 2 Ao: 2 oo P: 2: type A blood : 2 type o blood

Sex-Lined Traits gene carried only on the X chromosome there is no corresponding gene on the y chromosome Cross a non- colorblind male (XBY) with a “carrier” female (XBXb)

Law of Independent Assortment The distribution of alleles for one trait does not affect the distribution for of alleles for other traits

Law of Independent Assortment