Warm-up What do you already know about chromosomes? Tell me at least one thing!

Chapter 12

Human Genetics Learning 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 1 2 3 4 The pedigree shown traces Sudden Arrhythmia syndrome a recessive trait. Normal allele is: N Recessive arrhythmia allele is: n Carriers are not indicated in the graph!!! What are the genotypes of the following individuals? 1 2 3 4 5 5

Pedigree Practice 1 2 3 4 The pedigree shown traces Sudden Arrhythmia syndrome a recessive trait. Normal allele is: N Recessive arrhythmia allele is: n Carriers are not indicated in the graph!!! What are the genotypes of the following individuals? 1 Nn 2 Nn 3 Nn 4 nn 5 nn 5

Genetic Traits Single Allele Traits Recessive Single Allele Traits Examples: Phenylketonuria (PKU) Albinism Cystic Fibrosis You must inherit both recessive alleles from your parents…. to get the trait!!!

Genetic Traits Single Allele Traits Dominant Single Allele Traits Examples: Huntington’s disease: Polydactyly Cataracts If you inherit only one dominant allele…. You will get the trait!!!

Genetic Traits Mutiple Allele Traits Polygenic 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 Color Height

Example Polygenic Trait: Eye Color

X-linked Traits A trait which is controlled by a gene found on the X chromosome Examples: Colorblindness Hemophelia

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 blindness X – normal allele Y – 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!