Inheritance Patterns Mendelian and Complex

I. Simple Recessive Disorders A. Cystic Fibrosis 1. accumulation of thick mucus in the lungs and digestive tract 2. person’s affect literally can drown in their own mucus

Cystic Fibrosis

I. Simple Recessive Disorders B . Tay-Sachs Disease 1. lack of an enzyme that breaks down lipids created in the brain 2. fat builds up in the brain, destroys brain tissue – baby dies by age of 2

Tay-Sachs Disease

I. Simple Recessive Disorders C. Phenylketonuria (PKU) 1. person lacks enzyme (phenylalanine hydroxylase ) that breaks down the amino acid phenylalanine 2. amino acid builds up and damages nervous system

II. Simple Dominant Disorders A. Huntington’s Disease 1. caused by a DOMINANT allele – only have to have one copy to get the disease 2. causes holes in the brain where tissue has been broken down

phenylalanine hydroxylase

Normal Brain with Tumor

Huntington’s Disease

III. Complex Inheritance Patterns A. Incomplete Dominance 1. type of inheritance pattern where the recessive and dominant phenotype are blended together

III. Complex Inheritance Patterns Example: Red Snapdragons x White Snapdragons Red (RR) x White (R`R`) Pink (RR`) * because the recessive trait appears to be stronger, we won’t write it as “r” – designate as R`

Incomplete Dominance

Incomplete Dominance R R R`

Incomplete Dominance R R R` RR` RR`

III. Complex Inheritance Patterns B. Co-dominance 1. situation where BOTH alleles are equally dominant 2. both alleles expressed equally – not blended

Co-Dominance P Generation: Black-feathered Chicken x White-feathered Chicken F1 Generation: Checkered Chickens

Co-Dominance B B W

Co-Dominance B B W BW BW

Checkered Chicken

III. Complex Inheritance Patterns C. Multiple Alleles 1. trait that has more than 2 alleles 2. Blood Types a. IA, IB, i b. A, B, AB, and O

Blood Type Chart

III. Complex Inheritance Patterns D. Sex-Linked Inheritance 1. normal traits found on sex chromosome are ONLY found on the X 2. Females require 2 copies (XX) for the trait – males only require 1 copy (XY)

Colorblindness Normal Vision Allele: XB Colorblindness Allele: Xb Let’s say Mom is a normal vision person who is homozygous dominant for the normal vision allele. Her Genotype is: XBXB Let’s say Dad is colorblind: XbY

Colorblindness If they have another child, what are the chances that they will have a colorblind boy? P1 XBXB x XbY

Colorblindness XB XB Xb Y

Colorblindness XB XB Xb XBXb XBXb Y XBY XBY

Colorblind Tests Everyone should be able to see the circle, square, and star

Colorblind Tests Colorblind people ONLY see the yellow square.

Colorblind Tests Colorblind people ONLY see the yellow circle.

Colorblind Tests

What Colorblind People See