Download Chapter 5 Section 2

Incomplete Dominance
and
Meiosis Notes
Incomplete Dominance
 Sometimes
one
trait is not
completely
dominant over
another
 Both alleles have
a degree of
influence

Codominance
 There
is neither
a dominant or
recessive trait
 Both are
expressed
independently

Roan cattle are
crossed from white
and red cattle,
resulting in red cattle
with white blotches
Sex Cells
 An
egg or sperm cell
 A sex cell carries half the
number of chromosomes
found in other body cells
 Eggs – female sex cell
 Sperm – male sex cell
Review Mitosis
 Interphase
 Prophase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis
Mitosis vs. Meiosis
 Mitosis
is cell
division to
produce new
cells
 New cells are
identical to the
original cell
 Meiosis
is cell
division to
produce sex
cells
 New cells are
not identical to
the original cell
Meiosis
 Chromosomes
are duplicated
once, and the
nucleus divides
twice
 Making of sex
cells
Prophase 1
 Metaphase 1
 Anaphase 1
 Telophase 1
 Prophase 2
 Metaphase 2
 Anaphase 2
 Telophase 2

Sex Chromosomes
 The
chromosomes that carry
genes that determine the sex
of offspring
 Eggs contain only the X
chromosome
 Sperm contain an X or Y
chromosome
Cells vs. Chromosomes
 Sex
cells are eggs or sperm
that contain ½ the number of
chromosomes, including one
sex chromosome
 Sex chromosomes contain
genes that determine the
gender of offspring
50:50 Chance
 Male
sex
chromosomes
are XY
 Female sex
chromosomes
are XX
Sexual Reproduction
 Parent
cells are known as sex
cells or gametes
 Two parent cells join together to
form a new individual
 Gametes have half the number of
chromosomes in your body cells
Less is More
 Why
is it important that sex
cells have ½ the number of
chromosomes?
 Ensure the newly formed
offspring have the correct
number of chromosomes (46)
Homologous Chromosomes

Chromosomes with matching information