Variations on a Theme

What characteristics areShared by each of these Species?

Species Characteristics

Individualcharacteristics-make a person unique

Although your genes carry your

master plan there are other factors

that makeyou

YOU!

Like What?

Environment Spiritual life

Genetics- The Study of Heredity

Genes

A section of DNA that codes for a particular trait (the recipe for a protein)

Chromosomes

Threadlike structures composed of DNA

and proteins found in the nucleus of the

cell.

• Chromatid- one of the identical halves of the chromosome

• Centromere- constricted area where chromatids are joined

Homologous Pairs and Homologues

MITOSIS MEIOSIS

• Diploid- has two of each chromosome- 2n- product of mitosis

• Haploid- 1 of each chromosome- 1n- product of meiosis

Humans have 46 chromosomes or 23 pairs of chromosomes

Fruit Flies

8 chromosomes or 4 pairs

Goldfish

• 100 chromosomes or 50 pair

Crayfish

• 200 chromosomes or 100 pair

Lilies, Tomatoes, White Pines

• All have 24 chromosomes or 12 pair

• It’s not the chromosome number that determines the species but the genes on the chromosomes

What is a Karyotype?

• A photograph or stained, separated and sorted chromosomes

•

How many chromosomes would there be in a human diploid cell? A haploid cell?

Haploid cells are for reproduction

What is the difference between a gene and a chromosome?

Cell DivisionAnd the Cell Cycle

What is the cell cycle?

The life cycle of a cell

Interphase Mitosis Cytokinesis

Prophase

Metaphase

Mitosis

• The division of a cell to produce two identical daughter cells

Interphase•Chromosomes are copied•Appear as “threadlike”coils (chromatin)at the start, but each chromosome and its copy (sister chromosome) change to sister chromatids at end of this phase.

•Chromatid

Prophase•Mitosis begins•Centrioles appear•Spindle fibers form between the poles

Metaphase•Chromatids attach to spindle fibers in center

Anaphase•Chromatids separate and begin to move to opposite sides of the cell

Telophase•Two nuclei form•Chromosomes appear as chromatin (threads rather than rods•Mitosis ends

Cytokinesis•Membrane moves inward to create two daughter cells with identical chromosomes

Prophase

Whitefish Onion

Metaphase

Whitefish Onion

Anaphase

Whitefish Onion

Telophase

Whitefish Onion

All Together Now

Uses of Mitosis

• Growth

• Repair and replace old or damaged cells

• Asexual reproduction

MEIOSIS

Forming Gametes for Sexual Reproduction

Who discovered meiosis?

Van Beneden Studying Ascaris

Meiosis Vocabulary

• Zygote- a diploid cell formed by the union of a haploid sperm and egg

• Meiosis- the forming of sexual gametes by reducing the number of chromosomes from diploid to haploid through two divisions.

Meiosis- two divisions

• 1st division reduces the # of chromosomes from diploid to haploid

• 2nd division doubles the number of cells

Meiosis

Comparison of Mitosis and Meiosis

Compare Metaphase:Mitosis Metaphase Meiosis Metaphase I

Compare Anaphase

Mitosis Anaphase Meiosis Anaphase I

Compare Daughter Cells Produced:

Mitosis Meiosis

Purpose of Meiosis

• To form gametes for sexual reproduction

• Four viable sperm are produced from spermatogenesis

• One viable egg produced from oogenesis

Meiosis Vocabulary

• Gametes- haploid cells that, when united, form a diploid zygote- ex. sperm, eg

Meiosis Vocabulary

• Fertilization- the process of forming a zygote

Meiosis Vocabulary

• Sperm- male gamete

• Egg- female gamete

Meiosis Vocabulary

Forming of Sperm Forming of Eggs

Meiosis Vocabulary

• Sexual Reproduction-The fertilization (union) of haploid gametes to produce offspring that are not genetically identical to either parent