Download Sex Cells - Hicksville Public Schools

AIM: What is the difference between
the chromosome number in our
body cells and gametes?
DN: What are gametes? How many
chromosomes are in the gametes of
humans?
What is Sexual Reproduction?
It involves the joining of two cells to begin the
development of a new individual.
These special cells are called: Sex Cells (Gametes)
What are the names of these sex
cells?
Egg cell
(Female)
Sperm Cell
(Male)
The joining of a sperm cell with
an egg cell is called fertilization.
How many chromosomes do we
have in our cells?
• 46 chromosomes
OR
• 23 pairs of
chromosomes
Karyotype
Why do we have 2 of each
chromosome?
One from mom and one from dad
Each pair of chromosomes are called:
Homologous Chromosomes
Homologous Chromosomes:
Mom
Eye Color B
Dad
G
Hair Color B
R
Gene
Part of a
chromosome
that codes for
a trait
Have genes that code for the same
trait, but may have different versions
of that trait
Chromatids
•are exact copies of
each other
•Used during cell
division
Homologous
chromosomes
•A pair of
chromosomes that
contain genes for the
same trait
• can have different
versions of that trait
•One copy from each
parent
How many chromosomes do the
offspring have after mitosis?
46X
Mitosis
46X
46X
Same amount
as the parent
cell
Humans = 46
Do our sex cells have 46
chromosomes? NO!!!
What would happen if our sex
cells did have 46 chromosomes?
46
+
46
Egg
92
Offspring
Sperm
The offspring would have 92
chromosomes
1. Egg- 23 chromosomes
A: Sexual Reproduction
B: Egg Cell/23 chromosomes 2. Sperm- 23 chromosomes
C: Zygote/46 chromosomes 3. Fertilization- Zygote
formed with 46
chromosomes
Sexual Reproduction:
23
+
23
Egg
Sperm
46
Offspring
Characteris
A fertilized egg cell is called a Zygote
The zygote has 46 chromosomes
1) Is the creation of a new individual from 2 parents.
2) Offspring are not genetically identical to the parents.
Sex Cells (Gametes)
• Sex Cells: SPERM and
EGG
• Sex cells
should have 1/2
the normal
number of
chromosomes
Chromosome Number
• Diploid cells: (2n) normal number
of chromosomes (Body Cells)
• Haploid cells: (n) ½ the normal
number of chromosomes (Sex
Cells)
Meiosis
•The process by which sex cells are
produced with half the number of
chromosomes.
Meiosis is 2 Cell Divisions
1st Cell Division
2nd Cell Division
1 Diploid cell
4 Haploid Cells
What is the end result of
meiosis?
46X
Meiosis
23X
23X
4 cells with ½
the number of
chromosomes
23X
23X
Where does meiosis
occur?
Gonads – Ovaries
and Testis
Why is meiosis important?
• Maintains the number
of chromosomes from
generation to
generation
• Provides genetic
variation
• .
Gametogenesis
Gameto = gametes
Genesis = creation
Production of gametes (sperm & egg)
By meiotic cell division
Oogenesis
Creation of
an ovum or
egg cell by
meiotic cell
division in
the ovary.
How many eggs are produced?
•There is an unequal sharing of cytoplasm
•1 egg & 3 non functional polar bodies
Egg vs. Polar Bodies
The egg is very large, has most of the
cytoplasm, which will provide nutrients
for the offspring.
Spermatogenesis
Creation of sperm
cells by meiotic
cell division in the
testes.
How many sperm are produced
by spermatogenesis?
4 equal sized sperms
with flagella for
swimming.
Spermatogenesis vs.
Oogenesis
Practice Problems: