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Tuesday, November st 1 ! • HSAP is next semester! Let’s practice with some biology—write your answers in your journal—remember, notebook check coming up VERY soon. • You have 5 minutes after the tardy bell RINGS to complete this. That’s it. We’ll go over it tomorrow. GET BUSY and STAY BUSY today. • Page 172 in your book • “Interpret a Bar Graph” Section, Questions 1-3 6.1 KEY CONCEPT Gametes have half the number of chromosomes that body cells have. YOU have 2 major cell types! Body cells Most of body tissues, organs NOT passed on to kids body cells Develop from germ cells (In ovaries and testes) Gametes = sex cells (egg and sperm)! DNA IS passed to kids sex cells (sperm) sex cells (egg) Your cells have autosomes and sex chromosomes! • Your body cells have 23 pairs of chromosomes! – Homologous pairs = same structure. – One chromosome comes from each parent. • Autosomes = chromosome pairs 1-22 • Sex chromosomes = X and Y, determine gender are chroms #1 – 22, NON-sex chroms (have lots of other genes) A Homologous pair = 1 from each parent!! (same genes, but may “code” for diff traits) Pair #23 = Sex chroms = X & Y, genes determine gender!! What’s the difference here??? •Body cells! •2 copies of every chromosome •Half the chromosomes comes from each parent! •Gametes! (sperm, egg) •1 copy of every chromosome: • 22 autosomes • 1 sex chromosome Body Cells How are these processes alike? Different?? Sex Cells!!! Body Cells (Somatic) Body Cells Sex Cells (Gametes) Review!!! • Where are germ cells located in the human body? • What’s an autosome? • What’s a sex chromosome & how’s it different from an autosome? • In a human DIPLOID cell, how many chromosomes are there? • In a human HAPLOID cell, how many chromosomes? • After fertilization takes place (sperm meets egg), the resulting cell (zygote) is .... Diploid or haploid? • Do you think the Y chromosome contains genes that are crucial to the organism’s survival? • Does mitosis or meiosis occur more frequently in your body? 6.2 KEY CONCEPT During meiosis, diploid cells go thru 2 cell divisions to make haploid Meiosis = 2 rounds of cell division!! • Meiosis reduces chromosome number and creates genetic diversity! Meiosis I and meiosis II each have four phases, similar to those in mitosis!! •Similar, not identical – 1 from each parent (same genes) •Pairs separate in Meiosis I •Copies of the same chromosome! (each = ½ of duplicated chrom, attached @ centromere) •Separate in M. 2 Meiosis I • occurs after DNA has been replicated • divides homologous chromosomes into 4 phases. Turn to p. 174 – 175! Describe the steps of Meiosis!! • Meiosis II divides sister chromatids in four phases. • DNA is not replicated between meiosis I and meiosis II. How are they different???? – Meiosis = two cell divisions, mitosis = one – In mitosis, homologous chromosomes never pair up. – Meiosis results in haploid cells; mitosis results in diploid cells. Haploid cells develop into mature gametes. • Gametogenesis = production of gametes. • Gametogenesis differs between females and males! – Sperm become streamlined and motile. – Sperm mostly just contribute their DNA to the embryo. – Eggs contribute DNA, cytoplasm, and organelles to an embryo. Go GIRL! – During meiosis, the egg gets most of the contents; the other cells form “polar bodies”. More Review for you!!! • What is mitosis?? • What is meiosis? • What is a somatic cell?? • What are gametes??? • Examples of gametes??? • Examples of somatic cells?? • What are autosomes?? • Why are the X and Y chromosome special??? And MORE Review for you!!! • What is the difference between haploid and diploid cells?? • What is a homologous chromosome?? • A sister chromatid?? • What is gametogenesis?? Circle Activity for Meiosis Practice! Practice Sheet with Gametogenesis! • Smart Board Activity