This document summarizes different types of monohybrid crosses including: 1) Simple dominance for eye color and size where the dominant traits are expressed over recessive traits. 2) Sex-linked traits like skin color where the phenotype is determined by genes on the X chromosome. 3) Codominance where both alleles are expressed in the phenotype like different tail colors. 4) Incomplete dominance where the heterozygous phenotype is different than either homozygous phenotype like having 7 toes. The document provides the genotypes, phenotype ratios, and frequencies for each example.

1. Monohybrid Crosses
By: Kimberly Escobar 3rd period.

2. Simple Dominance: Color of Eye
(R= Red, r= black)
RR Rr
RR RrR
R
R r
Genotypic Ratio: 2(homozygous dominant) : 2 (heterozygous)
Genotype frequency: 50% RR, 50% Rr
Phenotype ratio: 4(red)
Phenotype Frequency: 100% (red)

3. 2 Simple Dominance: Size of the Organism
(B= Big, b= small)
Bb bb
Bb bb
b
b
B b
Genotype ratio: 2(homozygous recessive) : 2( heterozygous)
Genotype Frequencies: 50% Bb , 50% bb
Phenotype Ratio: 2 Big : 2 small
Phenotype Frequencies: 50% big , 50% small

4. Sex-Linked: Skin Color
( G= Gold, g= silver)
XGXG XGXg
XGY XgY
XG Xg
XG
Y
Genotypic Ratio: 1/4 homozygous dominant: ¼ heterozygous: ¼ hemizygous dominant : ¼
hemizygous recessive.
Phenotype ratio: ¾ gold: ¼ silver

5. Codominance: Tail Color
(TT=Red, Tt= Orange, tt= yellow)
TT Tt
Tt tt
T
t
t
T
Genotype Ratio: 1(homozygous dominant): 2 (heterozygous): 1(homozygous recessive)
Genotype Frequency: 25% TT, 50% Tt, 25% tt
Phenotype Ratio: 1 (red): 2( orange): 1(yellow)
Phenotype Frequency: 25% red, 50% orange, 25% yellow

6. Incomplete: Number of Toes
(CC=5 toes, cc= 6 toes, Cc=7 toes)
CC Cc
Cc cc
C c
C
c
Genotypic ratio: 1 homozygous dominant: 2 heterozygous: 1 homozygous recessive
Genotype Frequency: 25% homozygous dominant, 50% heterozygous, 25% homozygous
recessive
Phenotype Ratio: 1 (5 toes): 2 (7 toes): 1(6 toes )
Phenotype Frequency: 25%( 5 toes), 50% (7 toes), 25%( 6 toes)