The family tree of genetics

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Pedigree Charts

• The family tree of genetics

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Pedigree Charts
I
II
III
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What is a Pedigree?

• A pedigree is a chart of the genetic history of
  family over several generations.
• Scientists or a genetic counselor would find out
  about your family history and make this chart to
  analyze.

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Constructing a Pedigree

• Female

• Male

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Connecting Pedigree Symbols
Examples of connected symbols

• Fraternal twins
• Identical twins

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Connecting Pedigree Symbols
Examples of connected symbols

• Married Couple
• Siblings

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Example

• What does a pedigree chart look like?

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Symbols in a Pedigree Chart

• Affected
• X-linked
• Autosomal carrier
• Deceased

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Interpreting a Pedigree Chart

• Determine if the pedigree chart shows an
  autosomal or X-linked disease.
• If most of the males in the pedigree are affected
  the disorder is X-linked
• If it is a 50/50 ratio between men and women the
  disorder is autosomal.

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Example of Pedigree Charts

• Is it Autosomal or X-linked?

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Answer

• Autosomal

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Interpreting a Pedigree Chart

• Determine whether the disorder is dominant or
  recessive.
• If the disorder is dominant, one of the parents
  must have the disorder.
• If the disorder is recessive, neither parent has
  to have the disorder because they can be
  heterozygous.

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Example of Pedigree Charts

• Dominant or Recessive?

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Answer

• Dominant

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Example of Pedigree Charts

• Dominant or Recessive?

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Answer

• Recessive

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Summary

• Pedigrees are family trees that explain your
  genetic history.
• Pedigrees are used to find out the probability of
  a child having a disorder in a particular family.
• To begin to interpret a pedigree, determine if
  the disease or condition is autosomal or X-linked
  and dominant or recessive.

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Pedigree Chart -Cystic Fibrosis
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Human Genetics
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Karyotype
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Chromosome Number
Homologous Chromosomes are the sets of each pair

• Different for different species
• Full set 2NDiploid
• N
• pairs
• 1 pair from mother
• 1 pair from father
• Humans 23 pairs or
• 46 total

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Autosomes Sex Chromosomes
Autosomes 1-22 for all traits except sex
Sex chromosomes Pair 23 XX(female)
or XY(male)
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Down Syndrome 3 of 21
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Klinefelters XXY
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Multiple Alleles

• More than one type of allele for a trait
• Example
• Blood Type

• TYPES
• A IAIA, IAi
• B IBIB , IBi
• AB IAIB
• O ii

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Inherited Human Genetic Disorders

• Cystic Fibrosis
• Caused by a recessive allele
• Missing protein causes mucus build up in places
  like the lungs
• Most common among Caucasians

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Cystic Fibrosis
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Inherited Human Genetic Disorders

• Sickle Cell Anemia
• Caused by a co-dominant allele
• Altered protein changes the shape of red blood
  cells
• Most common among African Americans
• Heterozygous condition is resistant to malaria

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Sickle Cell Anemia
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Inherited Human Genetic Disorders

• Tay-Sachs
• Caused by a recessive allele
• Missing enzyme causes lipid build up in the brain
  (death by age 4)
• Most common among eastern European Jewish
  population

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Tay-Sachs
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Inherited Human Genetic Disorders

• Huntingtons Disease
• Caused by a dominant allele
• Late-onset of symptoms (age 40) result in the
  deterioration of nervous system

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Huntingtons Disease
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Inherited Human Genetic Disorders

• Phenylketonuria (PKU)
• Caused by a recessive allele
• Missing enzyme prevents the break down of
  phenylalanine (can cause brain damage)
• If caught early, an altered diet can prevent the
  damage

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PKU
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Karyotyping

• A karyotype is an ordered display of an
  individuals chromosome.
• Scientist take a picture of the chromosomes
  during metaphase.
• Each chromosome is paired with its homologue.
• Is used to detect abnormalities.

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Karyotyping
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Errors in Cell Division

• Nondisjunction is the failure of chromosomes to
  separate correctly (in meiosis I)

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Errors in cell division

• Produces 2 different types of gametes
• One with an extra chromosome
• Trisomy
• The zygote has 3 copies of one chromosome
• One missing a chromosome
• Monosomy
• The zygote has only 1 copy of a chromosome

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Genetic Disorders (Chromosome Number)

• Down Syndrome
• Trisomy 21(3 copies of chrom. 21)
• Most common serious birth defect in the US
• Syndrome includes characteristic facial features,
  short stature, heart defects, and intellectual
  disabilities

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Genetic Disorders (Chromosome Number)

• Kleinfelters Syndrome
• XXY
• Have abnormally small testes are sterile some
  feminine secondary sex characteristics normal
  intelligence

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Genetic Disorders (Chromosome Number)

• Extra Y
• XYY
• No obvious differences, usually tall

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Genetic Disorders (Chromosome Number)

• Metafemales
• XXX
• Limited fertility, possible intellectual
  disability

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Genetic Disorders (Chromosome Number)

• Turner Syndrome
• XO
• Is the only viable monosomy
• Short stature fail to develop secondary sex
  characteristics internal sex organs do not
  mature making the sterile