Today’s Agenda Warm-up Act 63 review “Lecture”

Chromosomes, Genes, DNA and Factors that Influence Inherited Traits. Revisiting Cell Division and How it Relates to Genetics

Outline 2.What we Missed a. Mitosis Friday b. Meiosis Monday

Mitosis Def: part of eukaryotic division during which the cell nucleus divides. (Cell Division) Normal Cell Function and Stages G1= Cell Growth S= DNA replication G2= Preparation for Mitosis M= Cell Division (further broken into) Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

Phases of Mitosis (Cell Division) Prophase: first and longest, centrioles move to opposite sides of the nucleus, chromatin condenses into chromosomes, nucleus breaks down, spindles form. (p 247 Biology)

Phases of Mitosis (Cell Division) Metaphase: Chromosomes line up across the center of the cell, each chromosome is connected to a spindle fiber at it’s centromere.

Phases of Mitosis (Cell Division) Anaphase: Sister chromatids separate into individual chromosomes and are pulled apart.

Phases of Mitosis (Cell Division) Telophase: Chromosomes gather at opposite ends of the cell and loose their distinct shapes. Two nuclear membranes begin to form.

Phases of Mitosis (Cell Division) Cytokinesis: The cytoplasm pinches in half. Each daughter cell has an individual set of duplicate chromosomes.

Phase of Normal Cell Function Interphase: The cell grows and replicates its DNA and Centrioles.

Where is Mitosis observed? Single celled organisms (bacteria, yeast, amoeba, etc):a form of asexual reproduction Multi-cellular organisms: a way to allow for growth, replacement and repair

Where is Mitosis observed? Single celled organisms: asexual reproduction Plants: roots, cambium(growing tree rings), buds, etc. Animals: skin, hair, cells that grow, repair and are replaced.

Products no matter where observed One cell becomes two identical cells. The same number of chromosomes are found in each the parent, and the two “offspring cells N= number of chromosomes, N in parent, N in two off spring

Meiosis Def: process by which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell (p 276 Biology) Making of Egg and Sperm Cells

Meiosis I Stages Interphase I: Cells undergo a round of DNA replication, forming duplicate chromosomes

Meiosis I Stages Prophase: Each chromosome pairs with its corresponding homologous chromosome to form a tetrad It is during this process that chromosomes may exchange portions of their genes during “crossing- over” The result of this means that each of the resulting cells will be different than the parent cell.

Meiosis I Stages Metaphase I: Spindle fibers attach to the chromosomes

Meiosis I Stages Anaphase I: The fibers pull the homologous chromosomes towards oposite ends of the cell

Meiosis I Stages Telophase I and Cytokinesis: Nuclear membranes form. The cell separates into two cells.

Meiosis II Stages Prophase II: Meiosis I results in two haploid (half chromosome) daughter cells. One cell with 4 chromosomes at the start became 2 cells with 2 chromosomes each DNA is NOT replicated during these stages.

Meiosis Stages Metaphase II: the chromosomes line up in a similar way to the metaphase stage of mitosis

Meiosis Stages Anaphase II: The sister chromatids separate and move toward the opposite ends of the cell.

Meiosis Stages Telophase II and Cytokinesis: Meiosis II results in 4 haploid daughter cells

Meiosis This is the way that sex cells are formed, sperm and egg. The resulting 4 sperm cells are all genetically different. In females, the result is one Egg cell and 3 polar bodies that don’t play a role in reproduction.

Venn Diagram Make a Venn Diagram to help understand the processes of Mitosis, and Meiosis. Draw out all stages and what happens to chromosomes during the stages of both Mitosis, and Meiosis.

DNA and Chromosomes

SO we all know about the packaging of DNA into a double helix… But what is the structure composed of…base pairs, and Nucleotides Adenine, Thymine, Cytosine, Guanine G=C, A=T, bonded via hydrogen bonds. DNA wound tightly into Chromosomes, with certain chains of bases equaling specific genes.

Human Chromosomes (22 pairs + sex Chromosomes)

END This information should help to clear up the material that you will read about in Act 63, it will also appear on the test at the end of the unit.