Meiosis and Sexual Reproduction Notes

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Meiosis and Sexual Reproduction Notes

• To be used with Meiosis and Sexual Reproduction
  Guided Notes

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Before Meiosis lets look back at Mitosis
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Genes and Heredity

• Heredity -
• the passing of traits from parents to
  offspring.
• Genetics -
• the study of heredity (the passing of traits)
• Each human cell contains 30 thousand different
  genes

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Genes and Heredity

• Genes
• Factors that control organism traits or
  characteristics.
• Part of a chromosome containing the genetic code
• Passed on from parent to offspring.
• All of your genes are located
• on 23 pairs of chromosomes

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Alleles

• Alleles part of a gene that is located on a
• chromosome.
• Example
• Height(gene)
• tallness or shortness(alleles)
• The alleles determine
• how each gene is expressed.
• At least two alleles for one gene.
• Locus Location of gene on
• a chromosome.

T
T
t
t
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Chromosomes
Sister Chromatid
Chromosome
Homologous Chromosome
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• Homologous Chromosomes
• -a pair of chromosomes that contain genes for the
  same traits.
• -one chromosome is from mom the other from dad.
• -same size centromeres are in same location.

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Amniocentesis

• Amniocentesis
• a medical procedure used in prenatal diagnosis
  of chromosomal abnormalities.
• Chromosomes are taken from the
• amniotic fluid.

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Karyotype

• The chromosomes from the amniotic fluid are
  
• then placed on a karyotype.
• A karyotype is a chart
• of an organisms chromosomes.

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Karyotype

• Next, the chromosomes are matched up according
  to
• 1. if they came from mom or dad.
• 2. how tall they are.
• 3. centromere location.

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Karyotype

• A karyotype can reveal if a person
• 1. is, male or female
• 2. has a normal number of chromosomes
• 3. has an abnormal number of chromosomes.
• Example Downs syndrome

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Meiosis

• Meiosis
• A type of cell division where the chromosome
  number is reduced to half.
• The process in which cells undergo two dividing
  phases to form
• gametes.
• Meiosis only produces sex cells (gametes).

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Meiosis

• Gametes are your sex cells.
• Your egg and sperm cells.
• Sexual reproduction
• (sperm egg)produces a zygote.

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Meiosis
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Diploid vs. Haploid

• Diploid Number (2n) the number of chromosomes
  found in all body cells.
• Humans 46.
• -found in the somatic(body) cells
• Haploid Number (n) 1/2 the diploid number of
  chromosomes. Humans 23.
• found in the egg and sperm cells of a species

DIPLOID
HAPLOID
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Diploid vs. Haploid

• Organism Diploid (body cells) Haploid
  (sex cells)
• Human 46
• Chimpanzee 24
• Dog 78
• Fruit fly 4
• Garden pea 14
• Adders fern 1260

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48
39
8
7
630
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Terms

• Gametes
• eggs or sperm
• Gonads
• specialized organs in higher animals where the
  gametes are made
• Ovaries
• female gonads
• Testes
• male gonads

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Meiosis

• Meiosis I
• Has all the phases mitosis has. I P M A T
• Meiosis II
• Has all the phases meiosis I has,
• except Interphase. P M A T

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Prophase I of Meiosis

• During Prophase 1 crossing over takes place.
• Crossing over is the exchange of chromosome
  pieces.
• Crossing over increases the variability of the
  offspring
• This is why the offspring of sexual reproduction
  show many variations
• - Crossing over occurs only during Prophase I

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Mitosis vs. Meiosis
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Problems during Meiosis

• Normally, homologous chromosomes separate and
  move toward opposite poles of the cell.
• Problems during anaphase this disorder is called
  non Disjunction
• Nondisjunction the failure of homologous
  chromosomes to separate

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Nondisjunction

• Down's syndrome results from the nondisjunction
  of chromosome 21
• individual has an extra 21st chromosome

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Downs Syndrome Rates
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Mistakes in Mitosis can be Good

• polyploidy
• having an entire extra set of chromosomes
• Will result in the 3n or 4n number of chromosomes
• - Many plants are a result of polyploidy banana
  day lily

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Summary of Mitosis Meiosis

• 1. Meiosis is very similar to two divisions of
  mitosis.
• 2. The diploid number (2n) of chromosomes is
  reduced by half to the haploid number (n)
• 3. Eggs and sperm are formed
• Crossing Over causes lots of variations
• Variations rarely occur in MITOSIS
• Variations often occur in MEIOSIS

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Summary

• Mitosis is associated with asexual reproduction.
• Mitosis takes place in somatic (body) cells.
• What is produced from mitosis?
• Two identical daughter cells How many? 4
• 10. Meiosis is associated with sexual
  reproduction.
• Meiosis takes place in sex cells.
• Meiosis produces gametes and three polar bodies.