Ch 10 - 11

• Life cycle


  Generation-to-generation sequence of stages in reproductive history

  
  

  Conception to the production of its own offspring

  
  

  Offspring acquire genes from parents by inheriting chromosomes
• Asexual Reproduction


  Mitotic cell division producing genetically identical offspring
• Sexual Reproduction


  Offspring produced by combining chromosomes from two parents
• Mitosis


  Makes body cells (skin and stomach cells)

  
  

  Results in two identical diploid cells (two sets of chromosomes from each parent)
• Prophase


  Chromosomes are condensing/thickening
• Metaphase


  Chromosomes line up in the middle of the cell
• Anaphase


  Chromatids are pulled apart, and they move to opposite sides of the cell
• Telaphase


  The spindle disappears and the nucleus forms around each set of daughter chromosomes

  
  

  Cytokinesis follows
• Meiosis


  Next Cards
• Haploid


  Cells with one set of chromosomes (n)
• Diploid


  Cells with two sets of chromosomes (2n)
• Chromosomes


  Human body cells have 46 chromosomes

  Each parent contributes 23 chromosomes
• Homologous chromosomes


  Two chromosomes in a pair - normally one inherited from the mother and one from the father.

  
  

  - Same length

  - Same centromere

  - Carry the same genes that control the same inherited traits
• Meiosis


  Meiosis is for sexual reproduction

  
  

  Meiosis reduces the chromosome number from diploid (2n) to haploid (n); n= 23 chromosomes

  
  

  Two main stages of meiosis

  
  

  Four non-identical cells (gametes)

  Produces gametes (sperm and egg cells)
• Importance of Meiosis


  Meiosis produces four haploid daughter cells that are not identical

  
  

  This results in genetic variations among offspring

  
  

  Depending on how the chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result

  
  

  Genetic variation is produced during crossing over and during fertilization, when gametes randomly combine.
• Human Gametes


  Mature haploid male or female germ cell, unites with another of the opposite sex in sexual reproduction to form a zygote
• Meiosis I


  Homologous pairs separate
• Meiosis II


  Sister chromatids of each chromosome separate
• Stages of Meiosis


  Reduces the chromosome number by half through the separation of homologous chromosomes

  
  

  Involves two consecutive cell divisions called meiosis I and meiosis II
• Stages of Meiosis I

  The stages of Meiosis I:

  
  

  Interphase

  Prophase I

  Metaphase I

  Anaphase I

  Telophase I
• Interphase


  Chromosomes replicate

  Chromatin condenses
• Prophase I


  Pairing of homologous chromosomes occur

  
  

  Each chromosome consists of two chromatids

  
  

  The nuclear envelope breaks down

  
  

  Spindles form
• Prophase I (Crossing over)

  Crossing over produces exchange of genetic information

  
  

  Crossing over chromosomal segments are exchanged between a pair of homologous chromosomes
• Metaphase I


  Chromosome centromeres attach to spindle fibers

  
  

  Homologous chromosomes line up at the equator
• Anaphase I


  Homologous chromosomes separate and move to opposite poles of the cell
• Telophase I


  The spindles break down

  
  

  Chromosomes uncoil and form two nuclei

  
  

  The cell divides
• Stages of Meiosis II

  Prophase II

  Metaphase II

  Anaphase II

  Telophase II
• Prophase II


  A second set of phases begins as the spindle apparatus forms and the chromosomes condense
• Metaphase II


  A haploid number of chromosomes line up at the equator
• Anaphase II


  The sister chromatids are pulled apart at the centromere by spindle fibers and move towards the opposite poles of the cell
• Telophase II


  The chromosomes reach the poles and the nuclear membrane and nuclei reform
• Cytokinesis


  Cytokinesis results in four haploid cells, each with n (23) number of chromosomes
• Mendel's Law of Heredity


  Next Cards
• Gregor Mendel


  Austrian Monk and Scientist

  
  

  Studied the inheritance of traits in pea plants

  
  

  1860s
• Genetics


  Scientific study of heredity
• Heredity/inheritance


  The passing of traits to the next generation
• Mendel's Tests


  Mendel performed cross-pollination in pea plants.

  
  

  Mendel followed various traits in the pea plants he bred.

  
  

  Mendel crossbred plants by transferring pollen by hand

  - pollen from stamen of a different plant
• Trait


  Any characteristics that can be passed from parents to offspring
• Mendel studied 7 different traits

  Seed or pea colour

  Flower colour

  Seed pod colour

  Seed shape or texture

  Seed pod shape

  Stem length

  Flower position
• Hybrid


  An organism that receives different genetic information for a trait from each parent