Read the paragraph below and list a few traits that make you look different from other people. Think about the traits that make people unique. Some people are tall, while others are short. People can have brown, blue, or green eyes.

Meiosis Parents can produce many types of offspring. Families will have resemblances, but no two are exactly alike. Every cell has a nucleus. Every nucleus has chromosomes. The number of chromosomes depends on the species. Ex.  Humans have 46 GENES are located on chromosomes. genes control the TRAITS of the individual.

Meiosis The process of Meiosis creates gametes from your germ cells. Gametes are sex cells (sperm and eggs). These cells are haploid (1N=1 set). “N” is used to represent the number of chromosomes. Gametes combine to create a zygote (a fertilized egg) which is diploid (2N).

Meiosis Draw the above Chromosome Structure and Label. Each chromosome has many alleles, or alternate forms of genes. When GAMETES combine, the ZYGOTE (offspring- the fertilized egg) gets half from mom (23) and half from dad (23). ZYGOTES are diploid  (46). When sperm and egg meet, their chromosomes must match for the zygote to develop properly.

Meiosis The process of creating a gamete (sex cell) is called MEIOSIS. It is similar to mitosis, but  will produce 4 daughter cells that are each haploid. Oogenesis  - makes eggs (ovum)  Spermatogenesis - makes sperm

Meiosis  Crossing-over increases the number of possible gene (segment of DNA that codes for a trait) combinations. It increases genetic variation by reorganizing the chromosomes. Crossing-over occurs when arms of homologous chromosomes make contact and exchange genes. Example:

Crossing Over

Mitosis – Cell Division in Somatic (Body) Cells Meiosis – Cell Division in Gametes (Sex Cells) Number of Divisions 1 2 Number of Daughter Cells 4 Genetically Identical Yes No Number of Chromosomes same Each gamete has 23 chromosomes (1/2 from each parent) Where Somatic cells (body cells) Germ cells (sex cells) Purpose Growth and repair of body tissues Production of gametes for sexual reproduction.

Key terms/ideas: Trait give a description and identify where they are found. Describe Genes. What are homologous chromosomes? What are gametes? What is fertilization? What is Meiosis? What is Crossing Over? How does Meiosis create genetic diversity?

Karyotypes A karyotype is a pattern or picture of chromosomes from one cell grouped into pairs and organized by size (largest to smallest).

Karyotypes The first 22 chromosomes are called autosomes. The last set are the sex chromosomes (XX = Female or XY=Male).

How do doctors diagnose Down syndrome How do doctors diagnose Down syndrome? Down syndrome is also known as Trisomy 21.

From Lakota

From Lakota