Download 7th grade Ch.5 section 1

Human Inheritance
Ch. 5 section 1
• Different traits you see are determined
by a variety of of inheritance patterns.
• Some human traits are controlled by
single genes with two alleles.
• And others by multiple alleles.
Single genes with 2 alleles
• Some human traits are controlled by a
single gene with one dominant allele
and one recessive allele.
• They have two distinctly phenotypes.
Single Genes with multiple
alleles
• Some human traits are controlled by a
single gene that has more than two
alleles.
• Multiple alleles- 3 or more forms of a
gene that code for a single trait.
• Blood type is an example of this.
Sex chromosomes
• Sex chromosomes- are one of the 23
pairs of chromosomes in each body cell.
• Carry genes that determine whether a
person is male or female, also carry
genes that determine other traits.
Girl or Boy
• Girl= XX chromosomes
• Boy= XY chromosomes
fertilization
• When a sperm cell with an X
chromosome fertilizes an egg, it will
develop into a girl.
• When a sperm cell with a Y fertilizes an
egg, it will develop into a boy.