Cell Reproduction

Cell Cycle Interphase and Mitosis

DNA replication For most of a cells life chromosome is a single copy of DNA looking like But during the “s” phase of interphase the chromosome copies itself making sister chromatids joined in the middle by a centromere ChromatidSister Chromatids

Mitosis When a cell goes through the phases Prophase Metaphase Anaphase Telophase to make two “daughter” cells that are exactly identical to the original “parent” cell

Interphase prophase metaphase anaphase telophase 2 daughter cells in Interphase Mitosis: cell reproduction to make exact copies of cells

Meiosis A Different Type of Cell Division! Only occurs for the purpose of producing gametes (= sex cells) Only occurs in reproductive organs (Animals = testes and ovaries; Plants = stamen and ovaries)

Meiosis v.s. Mitosis Chromosomes (pair of sister chromatids) line up in homologous pairs (instead of singly) during prophase = TETRAD

Homologous Chromosomes Organisms have pairs of chromosomes with corresponding DNA sequences one from each parent. Homologous chromosomes are the same size their centromeres are in the same position they have the same number of genes, arranged in the same order.

Homologous chromosomes Karyotype = photograph of all of the human homologous chromosomes Note: each chromosome is single without its sister chromatid

Meiosis vs. Mitosis During Prophase 1 of meiosis, the chromosomes in the tetrads swap alleles Swapping alleles = crossing over

Meiosis, What’s the big deal? Meiosis is the reason that in sexually reproducing organisms genetic information varies between parent and offspring, Genetic information varies between offspring from the same parents.

Meiosis ensures genetic variation which is essential for evolution. Species genes/traits change from generation to generation. With a GREAT deal of time this can produce significant changes Meiosis

Meiosis: process to make sex cells Daughter cells made from Meiosis are NOT identical to the “parent” cell. Regular human body cell = 46 chromosomes (somatic cell = diploid cell = 2N) Human sperm and egg = 23 chromosomes (sex cells or gametes = haploid cell = N) Also crossing over happens where pieces of the original chromosomes exchange places.

Products of Meiosis Daughter cells have half the DNA of the parent cell The chromosomes in each of the 4 daughter cells are different as a result of crossing over. 4 daughter cells Parent cell

MEIOSIS: to make sex cells with half the original DNA. Parent cell 4 daughter cells with half of DNA from parent cell

Mitosis vs. Meiosis Parent cell 2 daughter cells with identical DNA to parent cell 4 daughter cells with half of DNA from parent cell Parent cell 2 diploid somatic cells4 haploid gametes

Mitosis vs. Meiosis Mitosis: results in two cells with identical chromosomes Meiosis: results in four cells with different chromosomes* chromosomes

hill.com/sites/ /student_view0/chapter2/animation__comparison_of_meio sis_and_mitosis__quiz_1_.html animation comparing meiosis and mitosis hill.com/sites/ /student_view0/chapter2/animation__comparison_of_meio sis_and_mitosis__quiz_1_.html hill.com/sites/ /student_view0/chapter2/difficult_multiple_choice.html questions starting at 15 hill.com/sites/ /student_view0/chapter2/difficult_multiple_choice.html 30 question quiz question quiz