1. Chromosomes & Meiosis

2. What is the difference between Chromosomes, DNA, and Genes?

3. Inquiry Lab: Exploring a Human Karyotype
Check out this animation to see how a karyotype is prepared in the lab!

4. What do the colored bands represent on a chromosome?
Chromosome 7 is
Pictured to the left.
The dark/light bands
represent genes on
the chromosome.

5. 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

6. Analyzing Karyotypes
A chromosome pair has the following characteristics:
One chromosome comes from mom and the other from dad.
Both are roughly the same size and shape.
Both have the same centromere location.
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. 23 B b

7. Chromosome Pairs vs. Duplicated Chromosomes
THINK! – How are chromosome pairs different from duplicated chromosomes?
Duplicated chromosomes are exact clones of each other.
Duplicated chromosomes are always attached at the centromere.
DEMO: Let’s look at how chromosome pairs can have different versions of genes! B b

8. 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

9. NOVA VIDEO Clip
Check out this NOVA video clip titled: Personal DNA Testing_12mins
Answer the questions on your ticket slip.
Also, think about whether or not you would want to have a personal DNA test done to reveal what your genes say about your health.

10. Meiosis Activity: Take out a red & blue colored pencil.
Let’s illustrate the process on our Graphic Organizer!

11. Visualizing Meiosis! United Streaming Video Clip: Meiosis (3:48)
Meiosis Animation_Glencoe
Pay attention to these video clips to see meiosis in action.

12. THINK! - Why is Meiosis so Important?
Sperm = 23 chromosomes
Egg = 23 chromosomes
Zygote = 46 chromosomes
Fertilization
MITOSIS

13. Accidents during Meiosis
Accidents during meiosis can cause some individuals to have an extra chromosome in a pair or a missing chromosome in a pair.
An extra chromosome is called a trisomy.
A missing chromosome is called a monosomy.
Down Syndrome is a disorder in which a person has an extra 21st chromosome.

17. Accidents during Meiosis
How do these accidents happen?
Sometimes chromosome pairs do not split properly during meiosis I.
Watch this animation to learn!