Chromosomes & Meiosis

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

Inquiry Lab: Exploring a Human Karyotype

Check out this animation to see how a karyotype is prepared in the lab!

– http://www.youtube.com/watch?v=7ShPzzrCetE

Chromosome 7 isPictured to the left.The dark/light bands represent genes onthe chromosome.

What do the What do the colored bands colored bands represent on a represent on a chromosome?chromosome?

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 KaryotypesA 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.

– http://www.youtube.com/watch?v=xp44Dp-m1cc&list=LPe665JQlBNHg&playnext=1&feature=autoplay

23

Bb b bB B

Chromosome Pairs vs. Duplicated ChromosomesChromosome Pairs vs. Duplicated Chromosomes

Chromosome pairs

DEMO: Let’s look at how chromosome pairs can have different versions of genes!

Duplicated ChromosomesTHINK! – How are chromosome pairs different from duplicated chromosomes?– Duplicated chromosomes are exact

clones of each other.– Duplicated chromosomes are always

attached at the centromere.

Bb b bB B

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

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.

Meiosis

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

Organizer!

Visualizing Meiosis!

United Streaming Video Clip: Meiosis (3:48)

Meiosis Animation_Glencoe

– Pay attention to these video clips to see meiosis in action.

THINK! - Why is Meiosis so Important?

MEIOSIS Sperm = 23 chromosomes

Egg = 23 chromosomes

Zygote = 46 chromosomes

Fertilization

MITOSIS

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.

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

• http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/