Mitosis is _____________________________________ REVIEW OF MITOSIS. Mitosis is _____________________________________ It refers to the process of replication of ___________ cells. Two purposes of mitosis: ____________ and __________ It results in __________________________________ (_______________________________________) CELL DIVISION/REPRODUCTION BODY REPAIR GROWTH TWO IDENTICAL DAUGHTER CELLS 2 CELLS WITH THE SAME DNA AS ORIGINAL CELL Meiosis - Chapter 3

You have body cells and gametes. somatic Body cells are also called _________________ cells. Germ cells develop into ______________. Germ cells are located in the _________ and ________. Gametes are sex cells: ______________________. Gametes have _______ that can be passed to offspring. gametes ovaries testes Egg and sperm DNA body cells sex cells (sperm) sex cells (egg)

KEY CONCEPT Gametes have ______________________ of ______________________ that body cells have. ½ the number chromosomes

2 Your cells have __________ different type of chromosomes: - ___________________ - Chromosomes that carry _____________ body traits - ________________ - chromosomes that carry genes specific to the ___________ of an organism AUTOSOMES ONLY SEX CHROMOSOMES SEX/GENDER EXAMPLES OF AUTOSOMAL TRAITS EXAMPLES OF SEX CHROMOSOME TRAITS

Your cells have autosomes and sex chromosomes. Your body cells have _______ pairs of chromosomes. Chromosome pairs # 1-22 are ________________. Sex chromosomes, # ______determine gender in humans. They are referred to as _________________ 23 Homologous pairs 23 X and Y

Understanding Homologous Chromosomes AUTOSOMES ____________________of chromosomes have the same structure. For each homologous pair, one chromosome comes _____________________. from each parent Allele for straight hair From Mom Gene for hair texture From Dad Allele for curly hair

Understanding Sex Chromosomes ____________________do _________ always have the same structure. Each parent still contributes one sex cell, BUT depending upon the parent, they can give either an _____________________. Sex Chromosomes NOT X or a Y

Body cells are diploid; gametes are haploid. Fertilization between egg and sperm occurs in sexual reproduction. Diploid (2n) cells have two copies of every chromosome. n represents the “pairs of chromosomes” Human = 2n = __46___________________________ Goldfish = 2 n = _96___________________________ Pea = 2n = __18______________________________ Body cells are diploid. Half the chromosomes __haploid_______________________.

Sex cells, (______________) are haploid. GAMETES ONLY ONE Haploid (n) cells have ________________ of every chromosome. Only contain DNA from ______________________ ONLY ONE PARENT - Gametes have ___ autosomes and __ sex chromosome. 22 1

MAINTAINED Chromosome number must be _____________ in animals. Many plants have more than two copies of each chromosome. Mitosis and meiosis are types of nuclear division that make _________________ types of cells. Mitosis makes more _________________ cells. (____________) Meiosis makes more __________________ cells.(____________) 2 DIFFERENT SOMATIC/BODY DIPLOID GAMETES/SEX HAPLOID

Meiosis makes _______________ cells from diploid cells. HAPLOID Meiosis occurs in _______________ cells. Meiosis produces _______________. (_________________) SEX GAMETES SPERM & EGG

Steps of Meiosis PROPHASE 1 METAPHASE 1 ANAPHASE 1 TELOPHASE 1 / PROPHASE 2 METAPHASE 2 ANAPHASE 2 TELOPHASE 2 ____________________________________

PROPHASE I Sister Chromatids Nuclear Membrane Centrioles Fibers Shorten and Thicken. “Double File” Find their “match” or pair up, (one from mom with one from dad) Move apart from one another Form between centrioles Begins to break down

METAPHASE I Sister Chromatids Nuclear Membrane Centrioles Fibers Stretch between two ends of the cell Become attached to the fibers, pulled to middle of cell Remains dissolved move to opposite ends of cell

ANAPHASE I Sister Chromatids Nuclear Membrane Centrioles Fibers Pairs pulled apart by fibers. Pairs are separated… Sisters/copies are still connected Still at cell’s poles Pull matching pairs apart Remains dissolved

TELEPHASE I Sister Chromatids Nuclear Membrane Cell Membrane Fibers DO NOT disappear Each end of cell has HALF the number of chromosomes. Chromosomes DO NOT unwind. Begins to pinch in until the cytoplasm is divided in half forming two new cells DOES NOT reform

PROPHASE II Sister Chromatids Nuclear Membrane Centrioles Fibers Still coiled Has not reformed Move apart from one another Re-form between centrioles

METAPHASE II Sister Chromatids Nuclear Membrane Centrioles Fibers Become attached to the fibers. Are pulled to middle of cell (Single File) Remains dissolved Move to opposite ends of cells stretched between ends of cell. Are attached to center of sister chromatids

ANAPHASE II Chromatids Nuclear Membrane Centrioles Fibers Still at cell’s poles Pull each chromatid toward opposite ends of cell Remains dissolved Sisters are pulled apart by fibers. Each chromatid is separate from its “sister”

Each end of cell has HALF and SINGLE chromosomes. TELEPHASE II Chromatids Nuclear Membrane Cell Membrane Fibers Begins to pinch in until the cytoplasm is divided in half forming two new SEX cells, (4 TOTAL) Each end of cell has HALF and SINGLE chromosomes. Begins to reform Begin to disappear

KEY CONCEPT During meiosis, diploid cells undergo _______ cell divisions that result in _______________ cells. 2 HAPLOID

Cells go through two rounds of division in meiosis. Meiosis reduces chromosome number and creates _______________________________. GENETIC DIVERSITY

Meiosis differs from mitosis in significant ways. Meiosis has _____ cell divisions while mitosis has one. In mitosis, _____________chromosomes never pair up. Meiosis results in ____________ cells; mitosis results in ______________ cells. 2 HOMOLOGOUS HAPLOID DIPLOID

Pairs of homologous chromosomes separate in ___________. Meiosis I and meiosis II each have four phases, similar to those in mitosis. Pairs of homologous chromosomes separate in ___________. Homologous chromosomes are ___________ but not identical. One from mom One from dad Brown Eyes - Blue Eyes Attached Earlobes -Free Earlobes Type B blood -Type A blood Sister chromatids divide in _____________. MEIOSIS 1 SIMILAR homologous chromosomes MEIOSIS II sister chromatids sister chromatids

Meiosis I occurs after DNA has been replicated. Meiosis I divides homologous chromosomes in four phases.

Meiosis II divides sister chromatids in four phases. DNA is not replicated between meiosis I and meiosis II.

So What Does The Process of Meiosis Look Like? MORE MEIOSIS MEIOSIS EXAMPLES MEIOSIS ANIMATION

Result in four sex cells The Point of Meiosis Result in four sex cells Each cell will have HALF the number of chromosomes as the original cell. Sex cells develop during puberty.

MEIOSIS MEN VS. WOMEN WHAT IS THE SAME? WHAT IS THE DIFFERENT? 4 CELLS ARE PRODUCED EACH CELL HAS ONLY HALF THE NUMBER OF CHROMOSOMES AS THE ORIGINAL WHAT IS THE DIFFERENT? MALES: ALL FOUR CELLS ARE “GOOD” SPERM FEMALES: 3 CELLS ARE CONSIDERED “POLAR BODIES” ONLY 1 CELL IS A VIABLE EGG (THIS IS DUE TO AN UNEVEN DIVISION OF CYTOPLASM DURING MEIOSIS)

Haploid cells develop into mature gametes. _________________ is the production of gametes. Gametogenesis differs between ____________ and __________. Gametogenesis MALES FEMALES Sperm become ____________ and _____________. Sperm primarily contribute ____ to an embryo. STREAMLINED MOTILE DNA Eggs contribute _______, _____________, and ____________ to an embryo. During meiosis, the ______ gets most of the contents; the other cells form _________________. DNA CYTOPLASM ORGANELLES DNA POLAR BODIES

Understanding Meiosis Starting with Prophase I, draw a cell undergoing MEIOSIS. Your original cell has 4 chromosomes. Make sure to include the cell membrane, nuclear membrane, chromosome, centrioles, and fibers.

MITOSIS VS. MEIOSIS What is the same? What is different? 1.__________________________________2.__________________________________3.__________________________________4.__________________________________5.__________________________________Process: __________________________________________________________ 1 1.__________________________________2.__________________________________3.__________________________________4.__________________________________5.__________________________________6.______________________7.____________________________________ 1 2 2 1 3 3 4 5 4 6 5 7

DID YOU KNOW? The sperm is the smallest cell in the body, whilst the egg is the largest, it is estimated that it will take 175,000 sperm to weigh as much as a female egg, which is a lot of sperm! Average males produce 150 million sperm daily! Females are born with all the oocytes (eggs) that they will ever have in a lifetime? Infertility: sperm counts drop as low as 20 million per ml