Chromosomes & Meiosis

Big Picture

MEIOSIS Sperm = 23 chromosomes

Egg = 23 chromosomes

Zygote = 46 chromosomes

Fertilization

MITOSIS

MeiosisProcess of creating sex cells with half the amount of DNA

SpermMale sex cell (23)

Egg Female sex cell (23)

Fertilizationprocess where egg and spermfuse together

ZygoteFirst cell created afterfertilization (46)

MitosisProcess to create identicalbody 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 KaryotypesIn 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 ChromosomesThe 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

Bb b bB B

Activity: Analyzing Karyotypes

L t H A

l T H a

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

5. For which trait(s) did mom and dad give the SAME versions of genes? curliness

6. For which trait(s) did mom and dad give DIFFERENT versions? Length, texture, coat pattern

Activity: Big PictureWork with your partners to explain each term shown to the right. Use your own words!

MEIOSIS Sperm = 23 chromosomes

Egg = 23 chromosomes

Zygote = 46 chromosomes

Fertilization

MITOSIS

MeiosisProcess of creating sex cells with half the amount of DNA

SpermMale sex cell (23)

Egg Female sex cell (23)

Fertilizationprocess where egg and spermfuse together

ZygoteFirst cell created afterfertilization (46)

MitosisProcess to create identicalbody 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/predictdisorder/

Gender:Female

Disorder:Trisomy in pair 21

Symptoms:Learning difficultiesUnique Facial featuresHeart Defects

Gender:Male

Disorder:Trisomy in pair 23

Symptoms:Less prominent malecharacteristics

Gender:Female

Disorder:Monosomy in pair 23

Symptoms:Female who can’t make egg cells (sterile)