Download Egg Genetics Vocab. Notes

P1
F1
F2
Why are all first
generation flowers
gray?
a. Gray is the dominant
color.
b. Gray is the recessive
color.
c. Gray is the darker
color.
d. It is just a
coincidence.
P1
F1
F2
What ratio explains
the gray flowers
and white flower
in the second
generation?
a.
b.
c.
d.
1 to 1
2 to 1
3 to 1
4 to 1
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 genepurple 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.
Phenotype
•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
Why can’t heterozygous pea plants
ever be white??