Warm-up
• What do you already know about chromosomes? Tell me at least one thing!
Chapter 12
Human GeneticsLearning Intention:
Understand how the patterns of genetic inheritance can used to identify and predict the occurrence of a
genetic trait.
Success Criteria:
• I can … both read and construct a pedigree to study a genetic trait• I can… predict the likelihood that a particular trait
will be passed from parent to offspring based on different inheritance patterns• I can… explain how non-disjunction can cause
human genetic disorders
Pedigrees
• What are you reminded of when you see or hear the word pedigree?
Pedigrees
• What are you reminded of when you see or hear the word pedigree?
• What does the term mean in reference to genetics?
Pedigrees • A family record that shows how a trait is inherited
over several generation• By studying pedigrees, scientists can see patterns
of inheritance.• Females are represented by • Males are represented by• People who have the trait are colored in
completely • People who are carriers of the trait are colored in
halfway
Dd DD
d d
Pedigree Practice
The pedigree shown traces Sudden Arrhythmia syndromea recessive trait. Normal allele is: NRecessive arrhythmia allele is: nCarriers are not indicated in the graph!!!What are the genotypes of the following individuals? 1 2 3 4 5
1 2
3 4
5
Pedigree Practice
The pedigree shown traces Sudden Arrhythmia syndromea recessive trait. Normal allele is: NRecessive arrhythmia allele is: nCarriers are not indicated in the graph!!!What are the genotypes of the following individuals? 1 Nn 2 Nn 3 Nn 4 nn 5 nn
1 2
3 4
5
Genetic Traits
• Single Allele TraitsRecessive Single Allele Traits
Examples: Phenylketonuria (PKU)AlbinismCystic Fibrosis
You must inherit both recessive alleles from your parents…. to get the trait!!!
Genetic Traits
• Single Allele TraitsDominant Single Allele Traits
Examples: Huntington’s disease: PolydactylyCataracts
If you inherit only one dominant allele…. You will get the trait!!!
Genetic Traits
• Mutiple Allele Traits• Controlled by 3 or more alleles• Example: Human blood type (3 alleles A, B, O)
• Polygenic Traits• Characteristic controlled by several genes• Examples:
Skin ColorHeight
Example Polygenic Trait: Eye Color
• X-linked TraitsA trait which is controlled by a gene found on the X chromosome
Examples: ColorblindnessHemophelia
• Question: Why are males more likely to have an x-linked trait?• Because males only have one X chromosome they are more likely to
have X-linked traits.
Practice Problem
• Cross a female carrier for Color Blindess (an X-linked trait) with a normal color vision male.
Xb – allele for color blindnessX – normal alleleY – normal allele
Are there any color blind females?
• Yes, If the mother was at least a carrier and the dad was color blind
• Sex Influenced Traits• The presence of specific male and female hormones affect the expression of
proteins for particular traits• Males and Females that have the same genotype, will have a different
phenotype!!!
Example: Pattern baldness
Nondisjunction
Chromosomal non-disjunction disorders• Monosomy – missing a chromosome• e.g. Turner’s syndrome – missing a sex
chromosome, only have an X
• Trisomy – have an extra chromosome• e.g. Down syndrome – extra 21st chrom.
Klinefelter syndrome – extra X chrom. XXY
Trisomy Monosomy
Journal: What are the possible modes of inheritance?• Autosomal or X-linked• Dominant or Recessive
Pedigree Practice!