MEIOSIS AND SEXUAL LIFE CHANGES

YOU MUST KNOW… THE DIFFERENCES BETWEEN ASEXUAL AND SEXUAL REPRODUCTION THE ROLE OF MEIOSIS AND FERTILIZATION IN SEXUALLY REPRODUCING ORGANISMS THE IMPORTANCE OF HOMOLOGOUS CHROMOSOMES TO MEIOSIS

YOU MUST KNOW… HOW THE CHROMOSOME NUMBER IS REDUCED FROM DIPLOID TO HAPLOID THROUGH THE STAGES OF MEIOSIS THREE IMPORTANT DIFFERENCES BETWEEN MITOSIS AND MEIOSIS THE IMPORTANCE OF CROSSING OVER, INDEPENDENT ASSORTMENT, AND RANDOM FERTILIZATION TO INCREASING GENETIC VARIABILITY

CONCEPT 13.1 OFFSPRING ACQUIRE GENES FROM PARENT BY INHERITING CHROMOSOMES

GENES ARE SEGMENTS OF DNA A LOCUS IS THE LOCATION OF A GENE OF A CHROMOSOME ASEXUAL REPRODUCTION – SINGLE PARENT, ARISE BY MITOSIS, CLONE SEXUAL REPRODUCTION – TWO PARENTS, RESULTS IN GREATER GENETIC VARIATION

BACTERIA REPRODUCE ASEXUALLY BY BINARY FISSION OR SEXUALLY BY CONJUGATION ONE COILED CHROMOSOME

CONCEPT 13.2 FERTILIZATION AND MEIOSIS ALTERNATE IN SEXUAL LIFE CYCLES

LIFE CYCLE THE GENERATION-TO-GENERATION SEQUENCE OF STAGES IN THE REPRODUCTIVE HISTORY OF AN ORGANISM FROM CONCEPTION TO PRODUCTION OF ITS OWN OFFSPRING

KARYOTYPE A PICTURE OF ITS COMPLETE SET OF CHROMOSOMES, ARRANGED IN PAIRS OF HOMOLOGOUS CHROMOSOMES FROM THE LARGEST PAIR TO THE SMALLEST PAIR MADE FROM A HUMAN SOMATIC CELL

HOMOLOGOUS CHROMOSOMES CONTROL THE SAME INHERITED CHARACTERISTICS EACH PAIR IS INHERITED FROM EACH PARENT NONSEX CHROMOSOMES - AUTOSOMES EXCEPTION- SEX CHROMOSOMES

MEIOSIS GAMETES – EGG AND SPERM, HAPLOID CELLS – n ZYGOTE – FERTILIZED EGG, DIPLOID – 2n MEIOSIS REDUCES THE NUMBERS OF SETS OF CHROMOSOMES FROM TWO TO ONE FERTILIZATION RESTORES THE DIPLOID NUMBER

CONCEPT 13.3 MEIOSIS REDUCES THE NUMBER OF CHROMOSOME SETS FROM DIPLOID TO HAPLOID

MEIOSIS PRECEDED BY THE REPLICATION OF THE CELL’S DNA (INTERPHASE) FOLLOWED BY TWO STAGES OF CELL DIVISION, MEIOSIS I AND II RESULTS IN FOUR DAUGHTER CELLS WITH THE HAPLOID NUMBER

PROPHASE I SYNAPSIS OCCURS (JOINING OF HOMOLOGOUS CHROMOSOMES ALONG THEIR LENGTH) FORMING TETRADS TETRADS UNDERGO CROSSING OVER WHICH INCREASES GENETIC VARIATION AREAS OF CROSSING OVER FORM CHIASMATA (HOLDS THE HOMOLOGUES TOGETHER UNTIL ANAPHASE I) CENTRIOLES MOVE AWAY FROM EACH OTHER, THE NUCLEAR ENVELOPE DISINTEGRATES, AND SPINDLE MICROTUBULES ATTACH TO THE KINETOCHORES OF THE HOMOLOGUES

METAPHASE I HOMOLOGOUS PAIRS OF CHROMOSOMES ARE LINED UP AT THE METAPHASE PLATE MICROTUBULES FROM EACH POLE ATTACH TO EACH MEMBER OF THE PAIR

ANAPHASE I SPINDLES HELP MOVE THE CHROMOSOMES TOWARD OPPOSITE ENDS OF THE CELL SISTER CHROMATIDS STAY CONNECTED AND MOVE TOGETHER TOWARD THE POLES

TELOPHASE I HOMOLOGOUS CHROMOSOMES MOVE UNTIL THEY REACH OPPOSITE POLES EACH POLE CONTAINS A HAPLOID SETS OF CHROMOSOMES, WITH EACH CHROMOSOME STILL CONSISTING OF TWO SISTER CHROMATIDS

CYTOKINESIS DIVISION OF THE CYTOPLASM CLEAVAGE FURROW OCCURS IN ANIMAL CELLS CELL PLATE OCCURS IN PLANT CELLS RESULTS IN TWO HAPLOID CELLS

MEIOSIS II NO DUPLICATION OF CHROMOSOMES PROPHASE II – SPINDLES FORM AND SISTER CHROMATIDS MOVE TOWARD THE METAPHASE PLATE METAPHASE II – CHROMOSOMES ARE LINED UP ON THE METAPHASE PLATE ANAPHASE II – CENTROMERES OF THE SISTER CHROMATIDS SEPARATE AND INDIVIDUAL CHROMOSOMES MOVE TO OPPOSITE ENDS OF THE CELL

MEIOSIS II TELOPHASE II – CHROMATIDS HAVE MOVED ALL THE WAY TO OPPOSITE ENDS OF THE CELL NUCLEI REAPPEAR CYTOKINESIS – EACH OF THE 4 DAUGHTER CELLS HAS THE HAPLOID NUMBER OF CHROMOSOMES AND IS GENETICALLY DIFFERENT FROM THE PARENT CELL AND THE OTHER DAUGHTER CELLS

3 EVENTS OCCUR DURING MEIOSIS I THAT DO NOT OCCUR DURING MITOSIS SYNAPSIS AND CROSSING OVER DO NOT NORMALLY OCCUR DURING MITOSIS AT METAPHASE I, TETRADS ARE POSITIONED ON THE METAPHASES PLATE RATHER THAN INDIVIDUAL REPLICATED CHROMOSOMES AS IN MITOSIS AT ANAPHASE I, DUPLICATED CHROMOSOMES OF EACH HOMOLOGOUS PAIR MOVE TOWARD OPPOSITE POLES, BUT THE SISTER CHROMATIDS OF EACH DUPLICATED CHROMOSOME STAY ATTACHED. THE CHROMATIDS SEPARATE IN MITOSIS.

CONCEPT 13.4 GENETIC VARIATION PRODUCED IN SEXUAL LIFE CYCLES CONTRIBUTES TO EVOLUTION

IMPORTANT PROCESSES CROSSING OVER INDEPENDENT ASSORTMENT OF CHROMOSOMES – IN METAPHASE I, WHEN THE HOMOLOGOUS CHROMOSOMES ARE LINED UP ON THE METAPHASE PLATE, THEY CAN PAIR UP IN ANY COMBINATION RANDOM FERTILIZATION