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Pedigree Charts. The family tree of genetics. 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. Male. Female.

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pedigree charts

Pedigree Charts

The family tree of genetics

what is a pedigree
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.
connecting pedigree symbols
Connecting Pedigree Symbols

Examples of connected symbols:

  • Married Couple
  • Siblings
connecting pedigree symbols5
Connecting Pedigree Symbols

Examples of connected symbols:

  • Fraternal twins
  • Identical twins
slide7

Marriage

Has the trait

Female-daughter

Female-daughter

Male-Son

Male- Son

Oldest to youngest

Male-DAD

Female-MOM

interpreting a pedigree chart
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.
example of pedigree charts
Example of Pedigree Charts
  • Is it Autosomal or X-linked?
answer
Answer
  • Autosomal
interpreting a pedigree chart11
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.
example of pedigree charts12
Example of Pedigree Charts
  • Dominant or Recessive?
answer13
Answer
  • Dominant
example of pedigree charts14
Example of Pedigree Charts
  • Dominant or Recessive?
answer15
Answer
  • Recessive
slide16

ff

ff

Ff

ff

Ff

Key: affected male affected female

unaffected male unaffected female

Ff

  • Steps:
  • Identify all people who have the trait.
  • For the purpose of this class all traits will be given to you. In other instances, you would have to determine whether or not the trait is autosomal dominant, autosomal recessive, or sex-linked.
  • In this example, all those who have the trait are homozygous recessive.
  • Can you correctly identify all genotypes of this family?
    • F- Normal
    • f- cystic fibrosis
slide17

Key: affected male affected female

unaffected male unaffected female

Pp

Pp

  • PKU
    • P- Unaffected
    • p- phenylketonuria

Pp

pp

PP or Pp

pp

pp

Pp

Pp

slide18

Key: affected male affected female

unaffected male unaffected female

hh

Hh

  • H-huntington’s disease
  • h-Unaffected

Hh

hh

Hh

hh

hh

Hh

hh

summary
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.
autosomal dominant
Autosomal Dominant

Polydactyly

HD

Achondroplasia

Progeria

autosomal recessive
Autosomal Recessive
  • Disorders
    • Cystic Fibrosis
    • Tay-sachs Disease
karyotypes
Karyotypes
  • To analyze chromosomes, cell biologists photograph cells in mitosis, when the chromosomes are fully condensed and easy to see (usually in metaphase).
  • A picture of chromosomes arranged in this way is known as a karyotype.
karyotypes27
Karyotypes
  • The karyotype is a result of a haploid sperm (23 chromosomes) fertilizing a haploid egg (23 chromosomes).
  • The diploid zygote (fertilized egg) contains the full 46 chromosomes. (in humans)
labeling a karyotype
Labeling a Karyotype
  • To label a karyotype correctly, first list the number of chromosomes found in the karyotype. Ex. 46
  • Secondly, list the type of sex chromosomes found in the karyotype. Ex. XX
  • Lastly, list the any abnormalities at the appropriate chromosome number.

Normal Human Female: 46, XX

Normal Human Male: 46, XY

what are abnormalities
What are abnormalities?
  • Sometimes, during meiosis, things go wrong.
  • The most common error is nondisjunction, which means “not coming apart”.
  • If nondisjunction occurs , abnormal numbers of chromosomes may find their way into gametes, and a disorder of chromosome numbers may result.
autosomal chromosome disorders
Autosomal Chromosome Disorders
  • Two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with THREE copies of a chromosome.
  • This is known as a “Trisomy”
  • Trisomy 13, Trisomy 18, Trisomy 21.
down syndrome

Male: 47, XY, +21

Female: 47, XX, +21

Down Syndrome
  • Most common, Trisomy 21 (down syndrome)
  • 1 in 800 babies born in U.S. with Trisomy 21.
  • Mild to severe mental retardation
  • Increased susceptibility to many diseases and a higher frequency of other birth defects.
sex chromosome disorders

Klinefelter’s Syndrome, 47 XXY

Sex Chromosome Disorders
  • Turner’s Syndrome (nondisjunction)
    • Female inherits only one X chromosome
    • Karyotype: 45, X
    • Women are sterile, sex organs do not develop at puberty.
  • Klinefelter’s syndrome (nondisjunction)
    • Males receive an extra X chromosome
    • Karyotype: 47, XXY
    • The extra X chromosome interferes with meiosis and prevents ind. from reproducing.