Cell Division Mr. Hamilton Biology

Chromosomes Gene: Segment of DNA that codes for a protein. Chromosomes: Coiled structures that contain DNA and proteins. Humans have 46 chromosomes (23 Pair) Composed of chromatids attached by centromeres. Formed from DNA, Before cell division.

Chromosomes Homologous Chromosomes—Similar in shape and information Sister Chromatids—Occur in pairs 22 pair are autosomes (responsible for traits such as hair color, eye color, etc.) 1 pair of sex chromosomes (determines the sex of the offspring) Male—X Y Female—X X

Chromosomes Homologous Chromosome Sister Chromatids

Types of Division Binary fission: Occurs in Prokaryotes, because they don’t have a nucleus When dividing, the cell just pinches into two separate cells This is asexual reproduction.

Types of Division Eukaryotes must undergo mitosis because they have a nucleus Cell Cycle: Process of growth and development in eukaryotic cells. Includes: Interphase, Mitosis and Cytokinesis.

Cell Cycle Interphase: 90% of time is spent here. Normal activities of cell. Mitosis: Division of nucleus Cytokinesis: Division of cytoplasm.

Segments of DNA that code for a protein… Chromosome Chromatid Centromere Gene

How many chromosomes do we get from each parent? 12 23 24 46 15

How many sex chromosomes do humans have? 2 4 23 46 15

Bacteria divide by… Binary fission Cell cycle Mitosis Meiosis 15

Why do eukaryotes go through mitosis and not binary fission? They don’t have a nucleus They have a nucleus They are multicellular They are unicellular 20

Stages of Mitosis (Duplicates Cell) Interphase: The cell spends the majority of its time in this stage. Performs tasks that prepare the cell for cell division Chromosomes are not yet present.

Stages of Mitosis Prophase: Metaphase: Nuclear membrane disappear. Spindle fibers form—these help pull chromosomes apart. Chromosomes become visible Metaphase: Meta means middle Chromosomes line up in the middle/equator.

Stages of Mitosis (cont.) Anaphase: Centromeres duplicate Chromosomes are pulled apart to opposite poles. Telophase Nuclear membranes reappear. Spindles dissolve Cytokinesis begins Chromosomes uncoil

Where do cells spend the majority of their time Anaphase Interphase Metaphase Telophase 20

How many chromosomes will a cell have after mitosis if the original cell has 20? 10 20 23 46 20

Checkpoints The cell has checkpoints during growth and division. These help ensure that things are running smoothly. Changes or problems could result in the body’s immune system destroying cells. When problems are not caught, uncontrolled growth of cells results.

Chromosomal mutations Mutation: Any change in DNA. Two types: Somatic mutations: Occur in body cells after birth. Ex: Mutations causing cancer. Germ cell mutations: Occur in sperm/egg. Passed on to offspring. Ex: Down syndrome

Cancer Uncontrolled, rapid growth of unspecialized cells. Can be caused by both genetic and environmental factors. Tumors are not always cancer (malignant). Some are benign. A cancer causing agent is called a carcinogen.

Carcinoma: A type cancer that can form in epithelial tissue (skin). Sarcoma: Cancer that can form in connective tissue. (Muscle, bone, etc.) Leukemia: Cancer that invades blood forming tissue.

What is the correct order of Mitosis? Anaphase—Metaphase—Telophase—Prophase Anaphase—Metaphase—Prophase—Telophase Prophase—Metaphase—Anaphase—Telophase Telophase—Anaphase—Metaphase--Prophase 30

Which of the following occur because of mitosis? A cut will heal Bacteria will divide Sperm is produced Pollen is spread 20

UV rays cause DNA to be changed in the skin which results in rapid growth of cells. This could become… Dermatitis Eczema Ringworm Skin cancer 20

Meiosis Cuts chromosome number in half and creates haploid gametes (sex cells). Gametes are cut in half—after fertilization you have 46. Phases are same as Mitosis but they go through them twice.

Products of Meiosis Males: The process of Spermatogenesis produces 4 sperm cells. Each male produces 200-400 million sperm/day 2-5 ml of semen is released/ejaculation with 50-130 million sperm/ml Infertility occurs with as few as 20 million/ml Females: The process of Oogenesis produces 1 ovum and 3 polar bodies. In animals—these die. In plants—these form endosperm which nourish the seed until germination.

Types of Reproduction Asexual: Produces exact genetic copies of organisms. No joining of sperm/egg. Occurs in: bacteria and other microbes, hydra, rare in animals. Sexual: Produces offspring from joining sperm and egg. This can be external or internal fertilization.

Why sexual reproduction? Provides a blending of genes Too many of the same type of genes causes problems. Nature ensures that organisms are genetically stronger through sexual reproduction.

Genetic Variation Independent assortment: Chromosomes separate independently of one another. There are about 8 million possibilities. Crossing-over: Exchange of information between homologues during Prophase I. Random fertilization: The gametes that join are random and independent. 64 trillion possibilities from one couple.

Which of the following is asexual reproduction? Baby being born Bacteria dividing Chicken laying eggs Pollen being spread 20

An organism has 30 chromosomes in their body cells An organism has 30 chromosomes in their body cells. How many will be in their gametes? 10 15 30 60 20

What does meiosis produce? 1 egg and 1 sperm 1 egg and 4 sperm 4 eggs and 1 sperm 4 eggs and 4 sperm 20

What is the benefit of sexual reproduction? To provide a blending of genes To produce a lot of offspring quickly To produce clones of organisms To produce twins and triplets 20

Which type of division has more stages? Binary fission Meiosis Mitosis All have the same 20