Download Meiosis

Chromosomes & Meiosis
Meiosis
Process of creating sex cells
with half the amount of DNA
Big Picture
Sperm
Male sex cell (23)
MEIOSIS
Sperm = 23
chromosomes
Egg
Female sex cell (23)
Fertilization
MITOSIS
Zygote = 46
chromosomes
Egg = 23
chromosomes
Fertilization
process where egg and sperm
fuse together
Zygote
First cell created after
fertilization (46)
Mitosis
Process to create identical
body cells with the SAME
amount of DNA
How Do Scientists Make Karyotypes?
http://www.youtube.com/watch?v=7ShPzzrCetE
Analyzing Karyotypes
A picture of a person’s
chromosomes is called
a karyotype.
A person’s body cell
has 46 chromosomes
in total.
However, if we look
closely we can see 23
pairs of chromosomes.
23
Analyzing Karyotypes
In a karyotype there are 23
pairs of chromosomes.
– Pairs 1-22 are called
autosomes
– Pair 23 is called sex
chromosomes
Male & female karotypes are
different.
– Female’s 23rd pair = XX
– Male’s 23rd pair = XY
– THINK! – Is this karotype
showing a male or female?
The grey colored bands on
the chromosomes represent a
person’s genes.
23
Genes on Chromosomes
The chromosomes carry the person’s genes.
– Both carry the same order of genes.
– However, the genes on one chromosomes
may be a slightly different version from the
genes on the other chromosome.
– A person inherits one gene from mom and
one gene from dad.
– The two genes work together to give a
person his/her trait.
– THINK? – What is the eye color for each
chromosome pair?
• Bb = Brown eyes
• BB = Brown
• bb = blue
b B
B B
b b
Activity: Analyzing
Karyotypes
1. What is the puppy’s hair length?
Short
2. What is the puppy’s hair texture?
Silky
3. What is the puppy’s curliness?
Curly
4. What is the puppy’s coat pattern?
Spotted
L
t
H
A
5. For which trait(s) did mom and dad
give the SAME versions of genes?
curliness, texture
l
t
H
a
6. For which trait(s) did mom and
dad give DIFFERENT versions?
Length, coat pattern
Activity: Big Picture
Work with your partners to explain each term
shown to the right. Use your own words!
MEIOSIS
Sperm = 23
chromosomes
Sperm
Male sex cell (23)
Egg
Female sex cell (23)
Fertilization
MITOSIS
Zygote = 46
chromosomes
Egg = 23
chromosomes
Meiosis
Process of creating sex cells
with half the amount of DNA
Fertilization
process where egg and sperm
fuse together
Zygote
First cell created after
fertilization (46)
Mitosis
Process to create identical
body cells with the SAME
amount of DNA
Meiosis Animation
Meiosis
– Process used to make sex cells (egg or sperm)
– These cells have HALF the amount of DNA
Click on image to see the animation!
Accidents during Meiosis
Accidents during meiosis can cause some
individuals to have an extra chromosome or a
missing chromosome in his/her sex cell.
– An extra chromosome in a pair is called a trisomy.
– A missing chromosome in a pair is called a monosomy.
– http://learn.genetics.utah.edu/content/begin/traits/predic
tdisorder/
Gender:
Female
Disorder:
Trisomy in pair 21
Symptoms:
Learning difficulties
Unique Facial features
Heart Defects
Gender:
Male
Disorder:
Trisomy in pair 23
Symptoms:
Less prominent male
characteristics
Gender:
Female
Disorder:
Monosomy in pair 23
Symptoms:
Female who can’t
make egg cells (sterile)