Bellringer Title it Mitosis Review Bellringer 13119 1

Bell-ringer Title it ‘Mitosis Review Bellringer 1/31/19’ 1. What is the purpose of the Mitotic Cell Cycle? 2. How many cells does it start with? 3. How many cells does it end with? 4. How many chromosomes are in each human body (somatic) cell?

Sexually reproducing organisms contain two types of cells: Diploid cells ‘Body cells’ cells that contain two of each kind of chromosome (2 n) One chromosome from mom, and one chromosome from dad. Also called ‘Somatic Cells’ Haploid cells ‘Sex cells’ cells that contain only one of each chromosome (n) Also called ‘Gametes’

• In the body cells of animals and most plants, chromosomes occur in pairs. • In each pair, you inherited one from your mom, the other from your dad. From Mom From Dad

Homologous Chromosomes • The two chromosomes of a pair are called homologous chromosomes. • Each pair of homologous chromosomes has genes for the same traits.

Homologous Chromosomes • The two homologous chromosomes in a pair possess genes for the same traits. mom dad -same size -same shape -same genes located in the same place

Diploid Cells • A cell that contains two of each chromosome is called a diploid cell. • Body cells are also called SOMATIC cells • All of your body cells are diploid (2 n).

• Body cells (diploid) are different from sex cells. • Each person can only pass on ONE of their homologous chromosomes to their young. Each human parent passes 23 chromosomes to their young, so that when the sperm cell and egg cell combine- it will equal 46 Chromosomes.

Haploid Cells • So, sex cells CANNOT be diploid. • A cell containing only one of each chromosome is called a haploid cell (n). • Also called GAMETES

Sexual Reproduction Zygote

Sexual Reproduction During fertilization, the sperm (n) and egg (n) meet and create a zygote (2 n). ip d s T t’ a h ! d i lo

Diploid and Haploid Cells Chromosome Numbers of Common Organisms Organism Fruit fly Garden pea Corn Tomato Leopard Frog Apple Human Chimpanzee Dog Adder’s tongue fern Body Cell 8 14 20 24 26 34 46 48 78 1260 Sex Cell 4 7 10 12 13 17 23 24 39 630

In Humans, how many chromosomes would each of these cells have…. . CHEEK CELL 46 SPERM CELL 23 EGG CELL 23 NERVE CELL 46

Since they have different amounts of chromosomes, diploid and haploid cells are made in different ways ● Body cells are made division process MITOSIS. ● Sex cells are made by the division process MEIOSIS.

Before a cell can divide by either method, it must first prepare for cell division. The cell cycle (or entire life cycle of the cell) consists of: INTERPHASE: The longest/busiest stage in a cell’s life 1. Chromosomes (DNA) replicates 2. Cell grows bigger NUCLEAR DIVISION: Mitosis or Meiosis CYTOKINESIS: When the cytoplasm divides and the cell completely separates.

Now we will compare and contrast mitosis and meiosis Mitosis: Remember PMAT?

Mitosis: cell division that makes BODY CELLS. 46 It starts with a DIPLOID cell Chromosomes Replicate 92 46 46 It ends with TWO IDENTICAL DIPLOID cells

The kind of cell division that produces sex cells (haploid) containing half the number of chromosomes as a body cell, is called meiosis. Meiosis II

Meiosis: cell division that makes SEX CELLS. 46 It starts with a DIPLOID cell, Ends with FOUR HAPLOID cells Chromosomes Replicate 92 (not identical) 46 23 23 23

Meiosis • These haploid cells are called sex cells- gametes. • Male gametes are called sperm. They are created in the male sex glands, which are testes. • Female gametes are called eggs. They are created in the female sex glands, which are ovaries.

Babies! • When a sperm fertilizes an egg, the resulting zygote once again has the diploid number of chromosomes.

MALE MEIOSIS Spermatocyte Diploid Sperm (Haploid Gametes) FEMALE MEIOSIS Oocyte Diploid Eggs / Ova (Haploid Gametes)

So, does this mean when your sex cells are being produced you can only pass down genes from your mom OR genes from your dad? ?

No

***Crossing-Over*** During Meiosis: Homologous chromosomes (the two chromosomes of a pair) actually break and exchange traits- in a process known as crossing over.

FROM MOM This chromosome inherited by mom could code for straight hair, brown hair, and green eyes… FROM DAD After crossing-over This chromosome inherited by dad could code for curly hair, black hair, and brown eyes… Now one chromosome passed on to offspring could have traits from both homologous… curly hair, brown hair, and green eyes…

2 4 DNA replication during Interphase Crossing over occurs

c i t e n e ! G , tion k o ria o L Va 4 2 Each one of these chromosomes will go into separate sex cells. This is what makes the sex cells NOT identical…. causing genetic variation. 2