Aim #51: How do organisms create offspring
through sexual reproduction?
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.
1) How many chromosomes do we have in our
cells?
We have 46 chromosomes
in each our body cells.
We can also say that we
have 23 pairs of
chromosomes
Karyotype
2) Why do we have 2 of each chromosome?
We get one chromosome from each parent
3) Each pair of chromosomes are called:
Homologous Chromosomes
4) 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
5) How are chromatids different than
homologous chromosomes?
Chromatids are exact
duplicates of each other
Homologous chromosomes
have genes that code for
the same trait, but they may
code for different versions
of that trait
6) How many chromosomes do the offspring
have after mitosis?
46X
Mitosis
46X
46X
7) Do our sex cells have 46 chromosomes?
NO!!!
8) What would happen if our sex cells did have
46 chromosomes?
46
+
46
Egg
92
Offspring
Sperm
The offspring would have 92 chromosomes
9) Sexual Reproduction:
23
+
23
Egg
Sperm
46
Offspring
A fertilized egg cell is called a Zygote
10) Characteristics of Sexual Reproduction:
1) Is the creation of a new individual from 2 parents.
2) Offspring are not genetically identical to the parents.
Date: February 3, 2016
Aim #51: How do organisms create offspring through
sexual reproduction?
Do Now: Warm-Up Notebook
Date
Title of Activity
2/3
Asexual vs. Sexual Reproduction
Page #
89
HW:
1) Read Chapter 11-4 (Meiosis) pages 275-278 and
complete Cornell Notes Outline due Friday
–
Consider Section Assessment Questions (p. 278) in your summary
2) Yarn Lab due Friday!
11) Sex Cells (Gametes)
• Sex Cells:
SPERM and
EGG
• Sex cells should
have 1/2 the
normal number
of chromosomes
12) Chromosome Number
• Diploid cells: (2n) normal number
of chromosomes (Body Cells)
• Haploid cells: (n) ½ the normal
number of chromosomes (Sex
Cells)
Diploid vs Haploid
Diploid Cells
Haploid Cells and
Fertilization
13) Meiosis
•The process by which haploid (sex) cells
are produced with half the number of
chromosomes.
14) What is the end result of meiosis?
46X
Meiosis
23X
23X
23X
23X
15) Where does meiosis
occur?
Gonads – Ovaries
and Testis
16) Why is meiosis important?
• Maintains the number of
chromosomes from
generation to generation
• Provides genetic variation
• Only during fertilization
(union of sperm and egg) is
the full (diploid) set of
chromosomes restored.
Practice Problems: