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.

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.

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

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

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

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

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

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

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

Reading Graphic Organizer

Chromosome Lab

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.

Ticket Out What is the difference between haploid and diploid?