BSC 219

09/06/12

Pedigrees and human genetics

6.1 The Study of Genetics in Humans Is Constrained by Special Features of Human Biology and Culture

Special features:

Controlled mating is not possible

Long generation time

Small family size

Pedigree: pictorial representation of a family history, a family tree that outlines the inheritance of one or more characteristics

Proband: the person with whom the pedigree is initiated

Autosome Recessive Traits

Occur equally in both sexes

Tend to skip generations

Two unaffected parents have affected child

Autosomal Dominant Traits

Occur equally in both sexes

Unaffected parents will not have affected children

An unaffected person will have at least one affected parent

X-Linked Recessive Traits

Much more common in males than females

Affected male will not pass trait to son

Affected male will pass allele to daughter who could be carrier

Carrier females can have affected sons (50%)

X-Linked Dominant Traits

No skipping of generations

Affected males pass trait to daughters but not sons

Affected females pass trait to half of children

Y-Linked Traits

6.4 The Study of Twins Can Be Used to Assess the Importance of Genes and Environment on Variation in a Trait

Dizygotic twins = non-identical twins

Monozygotic twins = identical twins

Concordant trait: the trait shared by both members of a twin pair

Concordance: the percentage of twin pairs that are concordant for a trait

6.4 The Study of Twins Can Be Used to Assess the Importance of Genes and Environment on Variation in a Trait

Twin Studies and Obesity

6.6 Genetic Counseling Provides Information to Those Concerned about Genetic Diseases and Traits

Genetic counseling: provides information related to hereditory conditions

6.8 Comparison of Human and Chimpanzee Genomes Is Helping to Reveal Genes That Make Humans Unique

Microcephalin 1 to microcephalin 6 regulates human brain size.

FOXP 2 regulates human speech.