• Defined: Tightly

coiled DNA

• Form when cells

divide

– Chromosomes

created for the

new cells

• 2 Parts:

– 1) Chromatids:

two identical

parts of a

chromosome

– 2) Centromere:

Joins chromatids

together

• Defined: Picture of an

individual’s chromosomes

– Help identify sex &

chromosome defects

• Size of final pair identifies

sex

– Same size: XX = female

– Different size: XY = male

• Normal human will have 46

chromosomes per cell

Down Syndrome: What’s Wrong?

• Writing notation:

– 1st: total

chromosome #

– 2nd: Sex

chromosomes

– 3rd: extra or

missing

• Down Syndrome

47, XY, +21

Turner’s Syndrome: 30 seconds to discuss with your neighbor.

• Write the notation for Turner’s Syndrome.

45, X, -23

or

45, X0, -23

Patau’s Syndrome: 30 seconds to discuss with your neighbor.

• Write the notation for Patau’s Syndrome.

47, XY, +13

Klinefelter’s Syndrome: 30 seconds to discuss

with your neighbor.

• Write the

notation for

Klinefelter’s

Syndrome.

47, XXY, +23

• We inherit half our

chromosomes from each

parent (23 from mom; 23

from dad)

• Diploid Cells: Cells with full

set of chromosomes

– Paired chromosomes

– Humans: 23 pairs; 46

total

• Somatic (non-sex) cells are

diploid

– Ex: Skin, Muscle, Nerve, Blood

Cells

• Created by mitosis

• Haploid Cells = Cells with ½

the total number of

chromosomes

• Gametes (sex cells) are the

only haploid cells

– Ex: Sperm, Egg, Pollen

• Created by meiosis

– Chromosome number reduced

by half

• How do humans get 46

chromosomes?

Diploid Karyotype Haploid Karyotype

Diploid karyotype = Chromosomes

in pairs

Haploid karyotype =

Single chromosome

1 Minute: Discuss this rat

karyotype with your neighbor.

1) Gender?

2) Number of

chromosomes in

a somatic cell?

3) In a skin cell?

4) In a gamete?

5) In a diploid cell?

6) In a sperm cell?

Notice there are 21 pairs of chromosomes

1 Minute: Discuss this gorilla

karyotype with your neighbor.

1) Number of

chromosomes in

a haploid cell?

2) gamete?

3) In a muscle cell?

4) In a zygote?

5) In an egg cell?

6) In a somatic cell?Notice there are 24 pairs of chromosomes

Review1) What is the difference between chromatin, chromatids, and chromosomes?

2) Name the location where chromatids connect.

3) Examine the karyotype.

– What the haploid number?

– Diploid number?

– Somatic number?

– Gamete number?

4) What is the difference between autosomes and sex chromosomes?

5) Which of the following cells are created by mitosis?

Skin Nerve Sperm Brain Kidney Stomach Pollen

5) Which of the following cells are created by meiosis?

Skin Nerve Sperm Brain Kidney Stomach Pollen

6) Which of the following cells are haploid?

Skin Nerve Sperm Brain Kidney Stomach Pollen

7) Which of the following cells are diploid?

Skin Nerve Sperm Brain Kidney Stomach Pollen

8) A, B, or C: Which karyotype is from a diploid cell?

9) A, B, or C: Which karyotype could be from a muscle cell?

10) A, B, or C: Which two karyotypes could be from a sperm cell?

11) A, B, or C: Which karyotype is from an egg cell?

12) A, B, or C: Which two karyotypes are from a haploid cell?

Review