2. 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

3. 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

5. 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.

6. 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

9. 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

11. 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

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