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!