1. September 25, 2015 Bell Work: What is binary fission? Objective:
The student will be able to…
Describe the function of chromosomes.
Model mutations commonly found in chromosomes.

2. Today in History
1789 The first United States Congress adopted 12 amendments to the Constitution and sent them to the states for ratification. (Ten of the amendments became the Bill of Rights.)
1981 Sandra Day O'Connor was sworn in as the first female justice on the U.S. Supreme Court.

4. Sets of Chromosomes
Humans have 23 pair of chromosomes (46 chromosomes total)
Each chromosome contains genes essential to survival
Each pair of chromosomes has two homologous chromosomes or homologues
Homologous chromosomes are similar in size, shape, and genetic content
Each homologue comes from one of two parents

5. Sets of Chromosomes
Somatic cells: all cells in the body other than gametes
Somatic cells are diploid
Diploid: a cell that contains two sets of chromosomes
Gametes are haploid
Haploid: a cell that only contains one set of chromosomes

6. Sets of Chromosomes
n= the number of chromosomes (or sets of chromosomes) in a cell
Haploid cells are n
In humans, n= 23
Diploid cells are 2n
In humans, 2n= 46
Each organism has a characteristic number of chromosomes

8. Sex Chromosomes Two sex chromosomes are referred to as X and Y
Autosomes are chromosomes that are not directly involved in determining the gender of an individual
In humans, 22 of the 23 pairs are autosomes
Sex chromosomes contains genes that will determine the gender (sex) of the individual
In humans, only one of the 23 pairs are sex chromosomes
Two sex chromosomes are referred to as X and Y
The genes that cause a fertilized egg (zygote) to develop into a male are on the Y chromosome
Males: XY
Females: XX

9. Sex Chromosomes In crickets In birds, moths, and butterflies
Structure and number of sex chromosomes can vary in different organisms
In insects there is no Y chromosome
In crickets
Females are XX
Males are XO
O indicates the absence of a chromosome
In birds, moths, and butterflies
Males are XX
Females are X

10. Chromosome Number
A karyotype can be used to examine an individuals chromosomes
Karyotype: a photo of chromosomes in a dividing cell that shows the chromosomes arranged by size
Trisomy: humans with more than two copies of a chromosome (three copies of an individual chromosome
Trisomy 21: Down’s Syndrome
Characterized by short stature, round face with upper eyelids that over the inner corners of the eyes, and varying degrees of mental retardation

12. Chromosome Number
Disjunction: when a chromosome and its homologue separate
Nondisjunction: when a chromosome and its homologue fail to separate
Trisomy results when the gamete that receives two chromosomes due to nondisjunction fuses with a normal gamete

13. Reading Graphic Organizer

14. Chromosome Lab

15. Homework Notes Summarize your notes.
Summaries should be written in your own words, not the words that were provided for you on your note sheet.

16. Ticket Out
What is the difference between haploid and diploid?