Introduction to Genetics

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Introduction to Genetics

• Heredity and Mendels Peas
• Mrs. Stewart
• Honors Biology
• Central Magnet School

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Standards

• CLE 3210.4.1 Investigate how genetic information
  is encoded in nucleic acids.
• CLE 3210.4.2 Describe the relationships among
  genes, chromosomes, proteins, and hereditary
  traits.
• CLE 3210.4.3 Predict the outcome of monohybrid
  and dihybrid crosses.

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Objectives

• Differentiate between characteristics and traits
• Analyze Mendals principle of dominance
• Predict genotype based on phenotype
• Analyze characteristics and traits in this
  classroom

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Decide with your partner
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What is heredity?
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Why do familys look alike?
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Heredity Genetics

• Heredity - The transmission of characteristics
  from parents to offspring
• Genetics the study of heredity
• Genes Segments of DNA that code for a
  characteristic

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Characteristics vs. Traits

• Characteristic a feature
• Example flower color, hair color, number of
  fingers on your hand
• Trait a genetically determined variant of a
  characteristic
• Example purple flower color vs white, having 6
  fingers instead of 5

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Dogs

• Tell your cats two examples of characteristics
  that can be inherited from human parents to
  offspring.

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Cats

• Give your dogs an example of traits (variations)
  for the characteristics he/she listed.

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Gregor Mendel (1822-1884)

• Father of Genetics
• Austrian Monk
• Studied characteristics traits in pea plants
• Have only 7 chromosomes
• Can cross pollinate or self pollinate

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Flower Reproduction Reminder
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Gregor Mendels Peas

• Self pollination- Pollen from the plant
  fertilizes its own eggs
• Similar to asexual reproduction.
• True-breeding - produce identical new plants.
• Purebreds

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Mendels Peas

• Cross-pollination
• Remove male parts from true breeding plant,
  pollinate it with pollen from a plant with
  different traits.
• Produce hybrids
• Genetically different

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Mendels Observations

• Characteristics

• Traits

• wrinkled or smooth
• yellow or green
• white or grey
• smooth or constricted
• green or yellow
• axial or terminal
• tall or short

• Seed shape
• Seed color
• Seed coat color
• Pod shape
• Pod color
• Flower position
• Plant height

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Genotype VS. Phenotype

• GENOTYPE actual combination of alleles (genes)
  inherited from parents.
• (One from MOM, and one from DAD.)
• Example Tt, TT or tt
• PHENOTYPE physical appearance/expression of the
  trait.
• Example Tall plant or short plant

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Alleles

• We use letters to represent the variations
• Capital Letters Dominant allele
• Lowercase letters recessive allele
• Example T tall plant, t short plant
• Most genes have two or more variations (alleles)

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Cats and Dogs (think pair share)

• Phenotype

• Genotype

• Widows Peak or straight hair line

• Ww, WW or ww

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Important Vocabulary Terms

• HETEROzygous (DIFFERENT)
• have different alleles
• Example Tt
• HOMOzygous (SAME)
• have the same alleles.
• Example TT or tt

• HYBRID offspring of heterozygous parents
• PUREBRED (true-breeding) offspring of
  homozygous parents will produce offspring
  identical to parent traits

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Generations

• The parent generation
• The first generation
• The second generation

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Mendels experiments
P Purebred Tall x Purebred Short
F1 All tall (hybrids)
F2 31 ratio tallshort

• Tall height masks the effects of short height.
• Tall is dominant Short is recessive.

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Principle of Dominance

• some variations are dominant over others
• Dominant traits will mask or hide the presence of
  a recessive trait
• Recessive traits are hidden/masked by a dominant
  allele

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Principle of Dominance UFC style

• Only one can win
• Matt Hughes Recessive
• BJ Penn Dominant

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Principle of Dominance
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Cats And Dogs

• The dominant trait is gray fur, and the
  recessive trait is white fur. Lets use the
  following alleles Gray is G. White is g.
• If a bunny is heterozygous gray
• What is the genotype? ______________
• If a bunny is homozygous white
• What is the genotype? ______________
• If a plant is homozygous gray
• What is the genotype? ______________

Gg
gg
GG
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Principles of Dominance

• Predictable patterns of dominant and recessive
  only apply to single gene traits
• Example ONE gene is responsible for the type of
  hairline we have
• There are 2 alleles (variations) for this gene
• Possible Phenotypes widows peak (W) or straight
  hairline (w)
• Possible Genotypes WW, Ww or ww

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Dominance VS. Commonality

• Does dominant mean most common?
• Not necessarily
• Examples
• Polydactyl having 6 fingers
• Achondroplasia Dwarfism
• O blood type (recessive)

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Group Activity

• Inventory of Traits

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Dogs and Cats
Predict you and your partners possible genotypes
for the phenotypes listed in traits activity.
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Objectives

• Differentiate between characteristics and traits
• Analyze Mendals principle of dominance
• Predict genotype based on phenotype
• Analyze characteristics and traits in this
  classroom