Genetics

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Genetics

• Life Science
• Chapter 5

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Genetics and Inheritance

• Genetics ? the study of heredity that deals with
  the transmission of traits from one generation to
  another
• Inheritance ?The reception of traits by
  transmission from parent to offspring

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Genes and Chromosomes

• A Gene is a segment of DNA that controls a
  certain trait.
• Chromosome structures in the nucleus made up of
  many genes.

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Genotype and Phenotype

• Trait a feature that an individual has.
• ex eye color, nose size
• Genotype An organisms genetic makeup. It
  determines the traits an organism will have.
• Phenotype An organisms outward appearance.

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Gregor Mendel-1800s

• Considered to be the father of genetics
• Austrian monk, teacher and mathematician
• Expt. approach to genetics

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Gregor Mendel

• Parents pass on to their offspring factors
  (genes) that are responsible for inherited traits
• Used pea plants to study this

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Why peas?

• Rapid reproduction rate
• Presence of distinctive traits
• Closed structure of flowers (each pea plant has
  male (stamens) and female (carpal) sexual organs)
  allows self-fertilization

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Cross-fertilization

• One plant is fertilized by another

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Seven Traits Studied by Mendel
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Generations

• P- Generation Parental organism
• F1 generation Offsprings of cross between two
  parents
• F2 Offspring of cross between F1 generation

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Mendels Experiment

• Crossed pure purple and a pure white flower (P
  generation) F1 generation
• All F1 plants (purple) are crossed by self
  pollination F2 generation ?yields ¾ purple and
  ¼ yellow

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Gene Expression

• Genes control traits and expression of different
  traits
• Dominant Genes genes that keep other genes from
  showing their traits.
• ex Capital letters (TT for tall)
• Recessive Genes genes that donot show their
  traits when dominant genes are present.
• Lower case letters (tt for short)

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• Heterozygous an individual with one recessive
  and one dominant gene for a trait.
• ex Tt
• Homozygous an individual with either two
  recessive or two dominant genes.
• ex TT or tt

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Sex Chromosomes and Autosomes

• Autosomes Non sex chromosomes (44 in humans)
• Sex Chromosomes Chromosomes that carry the genes
  that determine the sex of an individual.
• shown by either X or Y
• Female? XX ( 1 from each parent)
• Male ? XY (X from mother, Y from father)

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• Male determines sex of offspring.
• All eggs ?1 X chromosome 22Autosomes
• Sperms? ½ have Y 22 autosomes
• ½ have X 22 autosomes

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Diploid and Haploid Cells

• Diploid Cells? Cells with 2 sets of chromosomes?
  total number of chromosomes? diploid or 2n
  Humans? 2n46 in somatic cells
• Haploid Cells ? 1n 23 chromosomes ? in sex
  cells, sperm egg (Gametes)

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Human Life cycle
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Meiosis

• Process by which haploid gametes are formed
• Alternation of meiosis and fertilization keeps
  the of chromosomes same from generation to
  generation.
• Mitosis? 2 offspring w/same of chromosomes

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Meiosis

• Gametes are formed? egg sperm
• 4 offspring with ½ the of chromosomes
• Exchange of genetic material? crossing over
• Oogenesis? production of egg? 1 egg 3 smaller
  polar bodies
• Spermatogenesis? production of sperm? 4 sperm
  cells

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Two Distinct parts of Meiosis
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Meiosis I
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Meiosis II