Genetics and Heredity

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Genetics andHeredity
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Deoxyribonucleic Acid (DNA)

• DNA is an organisms genetic material.
• Large molecule with a shape similar to a twisted
  ladder (double helix).

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• Chromosomes made of coiled DNA.
• Gene a section (pair) of a chromosome that has
  genetic information for 1 trait.
• Allele 1 copy of a gene. Each characteristic
  (trait) has two alleles, one from each parent.

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Traits are controlled by genes

• Genes are located on your chromosomes
• Individuals inherit genes from their parents
• Your cells contain 23 chromosome pairs

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What is a trait?

• Trait a physical characteristic that can be
  seen.
• Example of traits eye color, freckles, number
  of legs, thumb on top, rolling tongue.
• Each trait is represented by two letters (ex Tt).

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Heredity and Genetics

• Heredity passing of traits from parents to
  offspring.
• Genetics the study of how traits are passed
  from parent to offspring.

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The Father of Genetics

• Gregor Mendel
• Austrian Monk
• Gardener, bee
• keeper, scientist
• Experimented on
• plants, especially
• known for his
• work on pea plants.

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• Mendel studied 30,000 common pea plants over 8
  years and many generations. Mendel found that
  traits show up without any blending.

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Dominant vs. Recessive

• Dominant trait the allele that masks the
  appearance of another allele. Represented by a
  capital letter.
• Recessive trait the allele that is blocked by a
  Dominant allele. Represented by a lower case
  letter.

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• Dominant Traits

• Recessive Traits

• Broad lips
• Hazel or green eyes
• Second toe longest
• Widows peak hairline
• Crossing thumbs left on top
• Unattached earlobe
• Rolling tongue
• Dimples
• Freckles
• Straight thumb when extended
• Curly hair

• Thin lips
• Blue or grey eyes
• Big toe longest
• Straight hairline
• Crossing thumbs right on top
• Attached earlobe
• Non-rolling tongue
• No dimples
• No freckles
• Bent thumb when extended
• Straight hair

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The Punnett Square

• Reginald Punnett created the Punnett Square
• A tool used by scientists to predict the
  genotypes of offspring.

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Genotype Phenotype

• Genotype The two specific two alleles inherited
  for a particular gene (example TT, Ss, oo, Gg,
  etc.)
• Phenotype The observable characteristic that
  appears such as blue eyes, two legs, tallness,
  etc.

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Using the Punnett Square

• Draw the square

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Using the Punnett Square

• Write the genotypes of the parents on the
  outside of the box.

T t
T t
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Using the Punnett Square

• Fill in the boxes with the alleles down and
  across

T t
T t
T T
T t
t T
t t
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Using the Punnett Square

• Each box represents 1 offspring.
• In the above Punnett Square, how many different
  genotypes are there? How many different
  phenotypes are there? How can you represent
  those number in a percent ()

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Answers

• The genotypes are 1 or 25 BB , 2 or 50 Bb, and
  or 25 bb
• The phenotypes are 3 or 75 purple and or 25
  white

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Different types of Genotypes

• Heterozygous genotype a genotype in which the
  two alleles are different. (example Tt)
• Homozygous genotype a genotype in which the two
  alleles are the same. (example TT or tt)

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Different types of Genotypes

• Hybrid a heterozygous genotype and is the
  result of 2 genetically different parents.
• Example TT tt Tt
• Pure Bred a homozygous genotype and is the
  result of 2 genetically same parents
• Example TT TT TT or tt tt tt

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What is a pedigree?

• A pedigree is a chart of the genetic history of
  family over several generations.
• Show the phenotypes of genetically related family
  members.
• http//www.schooltube.com/video/c188ce8266b54a1899
  2b/tions

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Symbols in a Pedigree Chart
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Examples of Pedigrees