Heredity

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Heredity

• Domain 1 Cells and Heredity
• Heredity
• Ppt. 1

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Heredity

• Its in the genes!

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What is heredity?

• Heredity is the passing of traits from parent to
  offspring.
• You inherit traits from your parents

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What are traits?

• Eye Color
• Hair Color
• Height
• Weight
• Body Structure
• Facial Features
• Skin Color

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How traits are passed

• When organisms reproduce, traits are
• passed from parent to offspring.
• These traits are carried in DNA, the
• genetic material found in a cells
• nucleus.
• DNA acts like a blueprint.

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How are traits passed?
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Dominant and Recessive

• Each parent has two genes (or letters) for a
• trait. These letters are called alleles.
• Capital letters are called Dominant alleles.
• When these alleles are present, they take
• over or show. They are the stronger
• alleles
• Lower case letter are recessive alleles and
• are the weaker of the alleles.

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Genotype and Phenotype

• Genotype the inherited alleles (letters)
• Phenotype what the alleles look like when
  inherited.

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Genotype/Phenotype

• FF or Ff Freckles
• ff no freckles
• CC or Cc Curly Hair
• Cc straight hair
• TT or Tt Tall
• Tt short
• BB or Bb Brown
• bb blue

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Homozygous and Heterozygous

• IF the genes are the same, they are homozygous
  homo means same
• IF the genes are different, they are
• heterozygous hetero means different

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Putting it together Tall or short

• TT homozygous dominant tall
• Tt heterozygous tall
• tt homozygous recessive short
• Note a recessive trait (short) will be
  demonstrated only if the genotype is homozygous
  recessive tt

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Steps for Solving a Genetics Problem

• Trait dominant A (AA or Aa) Trait
  recessive a (aa)
• ___________ x ___________
• Punnett Square
• Answer questions based on results from Punnett
  Square

____ ____
____
____
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Monohybrid Crosses

• Cross that involves one pair of contrasting
  traits
• Solve using Punnett Square
• Sample problems
• Rr x rr
• RR x rr
• Rr x Rr
• Rr x RR

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Lets Solve Together

• Short hair (L) is dominant to long hair (l) in
  mice. What is the genotype and phenotype ratio
  of a heterozygous short-haired mouse crossed with
  a long-haired mouse?

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Example 1 Monohybrid

• Short hair dominant L (LL or Ll)
  long hair recssive l
• Ll x ll (heterozygote parent Ll)
• Punnett Square
• Genotype ratio ½ Ll ½ ll
• Phenotype ratio ½ short hair ½ long hair

L l
l Ll ll
l Ll ll
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Other Types of Heredity Patterns

• Incomplete Dominance blending of traits in
  heterozygote.
• Pink flowers
• RR red
• Rr pink
• rr white

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Other Types of Heredity Patterns

• Codominance can see both alleles at the same
  time.
• Roan coats in horses
• Some white hairs, some red hairs

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Multiple Alleles

• Blood Types in Humans
• Single gene, but four phenotypes
• Type A ? can be AA or Ao
• Type B ? can be BB or Bo
• Type AB ? only AB (codominant pattern here)
• Type O ? only oo (both recessive)
• All 3 blood types are dominant to O

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Continuous Variation

• Multiple genes are involved
• Examples
• Eye color
• Skin color
• Hair color

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Sex-linked Genes

• Present on the X chromosome
• More common in males
• When would a female have this phenotype?
• Examples
• Baldness
• Hemophilia

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Some Human Genetic Disorders Of Interest

• Cystic Fibrosis
• Sickle-cell Anemia
• Tay-Sachs Disease
• Phenylketonuria (PKU)
• Hemophilia
• Huntingtons Disease
• Muscular Dystrophy

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MUTATIONS

• Changes in DNA that affect genetic information

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Gene Mutations

• Point Mutations changes in one or a few
  nucleotides

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Gene Mutations

• Frameshift Mutations shifts the reading frame
  of the genetic message so that the protein may
  not be able to perform its function.

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Significance of Mutations

• Most are neutral
• Eye color
• Birth marks
• Some are harmful
• Sickle Cell Anemia
• Down Syndrome
• Some are beneficial
• Sickle Cell Anemia to Malaria
• Immunity to HIV

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What Causes Mutations?

• There are two ways in which DNA can become
  mutated
• Mutations can be inherited.
• Parent to child
• Mutations can be acquired.
• Environmental damage
• Mistakes when DNA is copied

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Chromosome Mutations

• Down Syndrome
• Chromosome 21 does not separate correctly.
• They have 47 chromosomes in stead of 46.

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Chromosome Mutations

• Cri-du-chat
• Deletion of material on 5th chromosome

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Sex Chromosome Abnormalities

• Klinefelters Syndrome
• XXY, XXYY, XXXY
• Male
• Sterility
• Small testicles
• Breast enlargement

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Sex Chromosome Mutations

• Turners Syndrome
• X
• Female
• sex organs don't mature at adolescence
• sterility
• short stature