6 1 Chromosomes and Meiosis REVIEW OF MITOSIS

6. 1 Chromosomes and Meiosis REVIEW OF MITOSIS. • • CELL DIVISION/REPRODUCTION Mitosis is ___________________ BODY It refers to the process of replication of ______ cells. REPAIR GROWTH Two purposes of mitosis: ______ and _____ TWO IDENTICAL DAUGHTER CELLS It results in _________________ 2 CELLS WITH THE SAME DNA AS ORIGINAL CELL (____________________) Meiosis - Chapter 3

6. 1 Chromosomes and Meiosis You have body cells and gametes. somatic • Body cells are also called _________ cells. • Germ cells develop into _______. gametes ovaries testes – Germ cells are located in the _____ and ____. Egg and sperm – Gametes are sex cells: ___________. DNA that can be passed to offspring. – Gametes have _______ body cells sex cells (sperm) sex cells (egg)

6. 1 Chromosomes and Meiosis KEY CONCEPT the number Gametes have ___________ of chromosomes ___________ that body cells have. ½

6. 1 Chromosomes and Meiosis 2 1. Your cells have _____ different type of chromosomes: AUTOSOMES - __________ - Chromosomes that carry ONLY _______ body traits -SEX ________ CHROMOSOMES- chromosomes that carry SEX/GENDERof an organism genes specific to the ______ EXAMPLES OF AUTOSOMAL TRAITS EXAMPLES OF SEX CHROMOSOME TRAITS Cleft in chin X linked trait Red-green color blindness Dimples Sex Linked Genes Shape of face

6. 1 Chromosomes and Meiosis Your cells have autosomes and sex chromosomes. • Your body cells have 23 _______ pairs of chromosomes. - Chromosome pairs # 1 -22 are Homologous pairs ________. • Sex chromosomes, # 23 ______determine gender in humans. They are referred to as X and Y _________ • Y chromosome is the smallest and carries the fewest genes

6. 1 Chromosomes and Meiosis 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

6. 1 Chromosomes and Meiosis Understanding Sex Chromosomes – __________do _____ always have Sex Chromosomes NOT the same structure. – Each parent still contributes one sex cell, BUT depending upon the parent, they can give either an X or a Y ___________.

6. 1 Chromosomes and Meiosis Body cells are diploid; gametes are haploid. • Fertilization between egg and sperm occurs in sexual reproduction. • Diploid (2 n) cells have two copies of every chromosome. – n represents the “pairs of chromosomes” Human = 2 n = __46______________ Goldfish = 2 n = _96______________ Pea = 2 n = __18_______________ – Body cells are diploid. – Half the chromosomes __haploid____________.

6. 1 Chromosomes and Meiosis GAMETES Sex cells, (_______) are haploid. ONLY ONE • Haploid (n) cells have ________ of every chromosome. ONLY ONE PARENT – Only contain DNA from ___________ 22 autosomes and __ 1 sex chromosome. - Gametes have ___

6. 1 Chromosomes and Meiosis MAINTAINED in animals. • Chromosome number must be _______ • Many plants have more than two copies of each chromosome. • Mitosis and meiosis are types of nuclear division that make 2 DIFFERENT _________ types of cells. SOMATIC/BODY cells. (______) DIPLOID • Mitosis makes more _________ GAMETES/SEX HAPLOID • Meiosis makes more _________ cells. (______) Result of Meiosis: 4 new cells, w/ ½ the DNA

6. 1 Chromosomes and Meiosis HAPLOID • Meiosis makes ________ cells from diploid cells. SEX – Meiosis occurs in ________ cells. GAMETES SPERM & EGG – Meiosis produces ________. (_________)

6. 1 Chromosomes and Meiosis PROPHASE 1 __________________ METAPHASE 1 __________________ ANAPHASE 1 __________________ TELOPHASE 1 / PROPHASE 2 __________________ METAPHASE 2 __________________ ANAPHASE 2 __________________ TELOPHASE 2 __________________

6. 1 Chromosomes and Meiosis Sister Chromatids Shorten and Thicken. “Double File” Find their “match” or pair up, (one from mom with one from dad) Nuclear Membrane Begins to break down Centrioles Move apart from one another Fibers Form between centrioles

6. 1 Chromosomes and Meiosis From mom From dad Sister Chromatids Become attached to the fibers, pulled to middle of cell Nuclear Membrane Remains dissolved Centrioles move to opposite ends of cell Fibers Stretch between two ends of the cell

6. 1 Chromosomes and Meiosis From dad From mom Sister Chromatids Pairs pulled apart by fibers. Pairs are separated… Sisters/copies are still connected Nuclear Membrane Remains dissolved Centrioles Still at cell’s poles From dad Fibers Pull matching pairs apart

6. 1 Chromosomes and Meiosis From mom From dad From mom Sister Chromatids Each end of cell has HALF the number of chromosomes. Chromosomes DO NOT unwind. Nuclear Membrane Cell Membrane Fibers DOES NOT reform Begins to pinch in until the cytoplasm is divided in half forming two new cells DO NOT disappear

6. 1 Chromosomes and Meiosis From mom From dad From mom Sister Chromatids Nuclear Membrane Still coiled Has not reformed Centrioles Move apart from one another Fibers Re-form between centrioles

6. 1 Chromosomes and Meiosis From mom From dad Sister Chromatids Nuclear Membrane Become attached to the fibers. Are pulled to middle of cell Remains dissolved (Single File) Centrioles Move to opposite ends of cells Fibers stretched between ends of cell. Are attached to center of sister chromatids

6. 1 Chromosomes and Meiosis From mom From dad Chromatids Nuclear Membrane Sisters are pulled apart by fibers. Remains dissolved Each chromatid is separate from its “sister” Centrioles Still at cell’s poles Fibers Pull each chromatid toward opposite ends of cell

6. 1 Chromosomes and Meiosis From mom From dad From mom Chromatids Each end of cell has HALF and SINGLE chromosomes. Nuclear Membrane Begins to reform Cell Membrane Begins to pinch in until the cytoplasm is divided in half forming two new SEX cells, (4 TOTAL) Fibers Begin to disappear

6. 1 Chromosomes and Meiosis KEY CONCEPT 2 During meiosis, diploid cells undergo _______ cell HAPLOID divisions that result in ________ cells.

6. 1 Chromosomes and Meiosis Cells go through two rounds of division in meiosis. • Meiosis reduces chromosome number and creates GENETIC DIVERSITY ________________.

6. 1 Chromosomes and Meiosis • Meiosis differs from mitosis in significant ways. 2 – Meiosis has _____ cell divisions while mitosis has one. HOMOLOGOUS – In mitosis, _______chromosomes never pair up. HAPLOID – Meiosis results in ______ cells; mitosis results in DIPLOID _______ cells.

6. 1 Chromosomes and Meiosis • Meiosis I and meiosis II each have four phases, similar to those in mitosis. MEIOSIS 1 – Pairs of homologous chromosomes separate in ______. SIMILAR – 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 homologous chromosomes MEIOSIS II – Sister chromatids divide in _______. sister chromatids

6. 1 Chromosomes and Meiosis • Meiosis I occurs after DNA has been replicated. • Meiosis I divides homologous chromosomes in four phases.

6. 1 Chromosomes and Meiosis • Meiosis II divides sister chromatids in four phases. • DNA is not replicated between meiosis I and meiosis II.

6. 1 Chromosomes and Meiosis MEIOSIS ANIMATION MORE MEIOSIS EXAMPLES

6. 1 Chromosomes and Meiosis Sex cells develop during puberty.

6. 1 Chromosomes and Meiosis • 4 CELLS ARE PRODUCED • EACH CELL HAS ONLY HALF THE NUMBER OF CHROMOSOMES AS THE ORIGINAL • 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)

6. 1 Chromosomes and Meiosis Haploid cells develop into mature gametes. Gametogenesis • _________ is the production of gametes. • Gametogenesis differs between MALES FEMALES ______ and _____. – Sperm become STREAMLINED ______ and _______. MOTILE – Sperm primarily contribute DNA ____ to an embryo. DNA – Eggs contribute _______, and CYTOPLASM ORGANELLES to an embryo. ______ DNA – During meiosis, the ______ gets most of the contents; the other POLAR BODIES cells form _________.

6. 1 Chromosomes and Meiosis

6. 1 Chromosomes and Meiosis Make sure to include the cell membrane, nuclear membrane, chromosome, centrioles, and fibers.

6. 1 Chromosomes and Meiosis

6. 1 Chromosomes and Meiosis 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

6. 1 Chromosomes and Meiosis