Why are all first generation flowers gray? P1 Why are all first generation flowers gray? Gray is the dominant color. Gray is the recessive color. Gray is the darker color. d. It is just a coincidence. F1 F2

P1 What ratio explains the gray flowers and white flower in the second generation? 1 to 1 2 to 1 3 to 1 d. 4 to 1 F1 F2

Review… Recall that most organisms have two sets of chromosomes (each chromosome has a matching pair. Humans have 23 pairs of chromosomes, so 46 chromosomes total.) Pairs of chromosomes have matching genes, therefore, genes also come in pairs, (2). Not all genes in a pair are identical! Ex.) There is one gene pair that controls flower color in pea plants, yet there are two forms of that gene- purple or white.

Allele One of two or more forms of a gene. One allele may be dominant over the other recessive allele. Ex.) alleles for eye color include brown and blue. Same gene, different form. Allele

Phenotype Genotype physical appearance what the trait will look like Determined by genotype Genotype type(s) of genes making up a trait (alleles) usually written as 2 letters representing a gene pair dominant trait is capitalized recessive trait is lower-case example: Ee or BB

Heterozygous Homozygous the alleles in a genotype are different (one is dominant and the other is recessive) “hybrid” Ex.) Pp = Purple flowers both alleles in a gene pair are the same (both dominant or both recessive) “true-breeding or purebred” Ex.) PP = Purple flowers pp = white flowers Heterozygous Homozygous

Why can’t heterozygous pea plants ever be white??