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Cellular Division

Learn about the different types of cellular division - mitosis and meiosis. Explore the reasons why cells divide, the process of reproduction, and how chromosomes play a role. Understand the differences between asexual and sexual reproduction.

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Cellular Division

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  1. Cellular Division Types of Reproduction Mitosis Overview Meiosis

  2. Why do Cells Divide? • A Larger Cell: • More demands placed on the DNA and organelles • DNA must control protein production for entire cell • If a cell is too big…..proteins can’t get where needed! • Diffusion of substances across the membrane becomes difficult • Volume increase faster than surface area (page 137) • Volume = L x W x H • Surface Area = L x W x 6 • Heal Wounds • Replace Dead Cells • To make new organisms…..Asexual Reproduction

  3. The Cell Cycle A series of events a cell goes through as it grows, metabolizes, and divides. • Interphase • G1 – Cell Growth • S – DNA Replication • G2 – Prepare for division • M-Phase = Mitosis! • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis

  4. Types of ReproductionAsexual – Production of offspring from one parentSexual – Production of offspring from combination of gametes Asexual – Binary Fission Asexual – Spore formation • When one cell splits into two • DNA replicates first! • Bacteria, protista • Kingdom Fungi!

  5. Types of ReproductionAsexual – Offspring are identical…no genetic variability Budding Regeneration • An unequal distribution of cytoplasm • The ability to grow new parts!

  6. Types of ReproductionAsexual – Offspring are identical…no genetic variability • Vegetative Propagation

  7. What is a Chromosome? • Chromosome – Made from DNA and Protein • DNA is wrapped around proteins called histones • Chromatin – Dense patches of lengthened chromosomes found in the nucleus • Contain genetic material! • Humans have 46 Chromosomes in their body cells (Somatic Cells)! • This is called the diploid number!!

  8. Terms to know: Chromosome, chromatid (sister chromatids), centromere,

  9. Sexual Reproduction • Reproduction from the combination of two gametes • Gametes are specialized Sex cells • Sperm – Male Gamete • Formed through the process of “spermatogenesis” • Takes place in the testes • Ovum (egg) – Female Gamete • Formed by the process of “oogenesis” • Takes place in the ovaries • Fertilization – The joining of an egg and sperm If an egg and sperm each have 46 chromosomes…..what will happen to the chromosome number of the offspring?

  10. Meiosis • Somatic Cells (body cells) – 46 chromosomes • This is called the diploid number (2n) • 23 pairs (#1 from mom, #1 from dad…etc) • Sex Cells (Sperm and egg) - 23 chromosomes • This is called the haploid number (n) • WHY 23? • You must reduce the number when making gametes • Our testes and ovaries undergo MEIOSIS • Two divisions instead of one. Sperm/Egg = 23 chromosomes • Fertilization will then restore the diploid number and mitosis begins again!

  11. Meiosis in Males and Females

  12. Fertilization

  13. Crossing Over Genetic Recombination!!

  14. b

  15. Mitosis/Meiosis Comparisons Mitosis Meiosis • One division • Two daughter cells • Daughter cells are diploid (46) - 2n • Two divisions • Four daughter cells • Daughter cells are haploid (23) - n • Males – Four Viable Sperm cells • Females – One egg and Three Polar Bodies

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