The document explains genetics, focusing on how traits are inherited, including definitions of key terms like genes, alleles, phenotypes, and genotypes. It describes homozygous and heterozygous conditions and illustrates monohybrid crosses using the example of albinism. The outcomes of crosses are used to determine whether an unknown genotype is homozygous dominant or heterozygous based on offspring traits.

2.  Genetics is the study of how
traits are inherited in offspring.

3.  Gene: Segment of
chromosome (DNA)
that codes for a trait

4.  Allele: Different
form of the same
gene.
 Example: Skin Color
(Color, Albino)

5.  Humans normally
have two alleles for
each gene.

6.  Dominant: Trait that
gets expressed
from dominant
allele.

7.  Phenotype: Observable physical
or behavioral trait

8.  Genotype: Genes (Alleles) that
code for a trait

9.  Homozygous: having the same
forms (alleles) for a gene on
both chromosomes.
 Also said to be purebred.

10.  Homozygous Dominant = AA
 Homozygous Recessive = aa

11.  Heterozygous: having different
forms (alleles) for a gene on
both chromosomes.
 Also said to be hybrid.

12.  Monohybrid Crosses
 Gene: Albinism
 Dominant Allele: A = normal
skin color
 Recessive Allele: a = albino
Heterozygous = Aa, or aA

13.  Cross a heterozygous individual
with a heterozygous individual:
Aa X Aa
Heterozygous = Aa, or aA
A a
A AA Aa
a Aa aa

14.  Cross a homozygous dominant
individual with a homozygous
recessive individual: AA X aa
Heterozygous = Aa, or aA
A A
a Aa Aa
a Aa Aa

15.  Test Cross: Cross a
homozygous recessive
individual with an unknown
(homozygous dominant or
heterozygous): aa X A?
Heterozygous = Aa, or aA
A ?
a Aa A?
a Aa A?

16.  The outcome determines the
offspring. If half of the
offspring are albino, then the
unknown is heterozygous (Aa).
Heterozygous = Aa, or aA
A a
a Aa aa
a Aa aa

17.  If all of the offspring have
normal skin color, then the
unknown is homozygous
dominant.
Heterozygous = Aa, or aA
A A
a Aa Aa
a Aa Aa