MEIOSIS 11-4 Making gametes…

Planaria animation: Family Remember from Chapter 1: CHARACTERISTICS OF LIVING THINGS ALL LIVING THINGS __________ REPRODUCE

ASEXUAL REPRODUCTION Bacteria reproduce using __________________________________ Budding & regeneration are used by plants and animals to reproduce asexually (mitosis) Planaria animation: BINARY FISSION

BINARY FISSION & MITOSIS Produces cells that are __________ copies of parent cell identical

SEXUAL REPRODUCTION Combines genetic material from 2 parents (sperm & egg) so offspring are genetically __________ from parents DIFFERENT Family image from:

ADVANTAGES OF SEXUAL REPRODUCTION Allows for variation in population Individuals can be different Provides foundation for EVOLUTION Allow species adapt to changes in their environment

EGG + SPERM  If egg and sperm had same number of chromosomes as other body cells... baby would have too many chromosomes! Image by Riedell

MEIOSIS is the way… to make cells with ½ the number of chromosomes for sexual reproduction

DIPLOID & HAPLOID Most cells have 2 copies of each chromosome = ______________ (one from mom; one from dad) All BODY (___________) cells are diploid DIPLOID2n HOMOLOGOUS CHROMOSOMES = SOMATIC

DIPLOID & HAPLOID Some cells have only one copy of each chromosome = _____________ All sperm and egg cells are haploid HAPLOID1n

MITOSIS Makes ___ cells genetically _________ to parent cell & to each other Makes ___ cells Makes __________ Used by organisms to: increase size of organism, repair injuries, replace worn out cells 2 identical 2n SOMATIC (body)

MEIOSIS Makes ____ cells genetically different from parent cell & from each other Makes _____ cells Makes ______________ Used for ____________ 4 1n Gametes (sperm & eggs) sexual reproduction

WHAT MAKES MEIOSIS DIFFERENT ? 1.Homologous chromosomes pair up during ________________ Images modified from: This group of FOUR (4) chromatids is called a _________________ TETRAD PROPHASE I

WHAT MAKES MEIOSIS DIFFERENT? 1. Exchange of DNA between homologous pairs = _____________ during PROPHASE I CROSSING OVER Allows shuffling of genetic material

HOMOLOGOUS CHROMOSOMES Image modified by Riedell SAME SIZE SAME SHAPE CARRY GENES for the SAME TRAITS BUT ______________! (Don’t have to have the SAME CHOICES) NOT IDENTICAL

CROSSING OVER Image modified by Riedell Allows for_________________ in different combinations After crossing over, chromatid arms are________________ anymore rearranging of DNA NOT IDENTICAL

Separation of homologous pairs (Anaphase I)

INDEPENDENT ASSORTMENT

Separation of homologous pairs at ANAPHASE I Lots of different combinations are possible! This is why you don’t look exactly like your brothers and sisters even though you share the same parents!

WHAT MAKES MEIOSIS DIFFERENT ? Crossing over MEIOSIS results in =______________________________ So daughter cells are ______________ from parents and from each other different GENETIC RECOMBINATION

WHAT MAKES MEIOSIS DIFFERENT ? INTERPHASE II (No S) shorter CELL DIVIDES TWICE, BUT … ONLY COPIES ITS DNA ONCE G1G1 G2G2 S   PM  A T C G1G1    MITOSIS: MEIOSIS:    SG2G2 PM ATC PM A TC ( I ) ( II )G1G1  G2G2

Ways Meiosis is different? Homologous pairs match up & trade DNA (CROSSING OVER) in PROPHASE I create genetic recombination INTERPHASE II- no S stage (Dividing TWICE but copying DNA once) produces 1n cells

MAKING SPERM & EGGS

___________________= MAKING MATURE SPERM Mature & grow flagella SPERMATOGENESIS

POLAR BODIES Produces: 1 “good” egg 3 CYTOPLASM DIVIDES UNEVENLY __________________ = MAKING a MATURE EGG OOGENESIS

Sperm donates mostly DNA WHY MAKE ONLY ONE “GOOD” EGG? Most of the cell parts and nutrients needed for baby come from EGG!

“Self digest” Using ________________ POLAR BODIES DEGENERATE (DIE) LYSOSOMES = __________________ “cell suicide” for good of organism APOPTOSIS