Complex Inheritance Patterns

1.Incomplete Dominance – phenotype of heterozygous is intermediate of the 2 homozygous phenotypes -results in the blending of traits -example: snap dragons

Alleles: R = red R’ = white Genotypes/Phenotypes RR = __________ R’R’ = _________ RR’ = __________ red white pink

Example Problem: Red snapdragon crossed with a pink snapdragon _______ X _______ Results: ___ of 4 red = _____% ___ of 4 pink = _____% ___ of 4 white = _____% RRRR’

human example of incomplete dominance: sickle cell anemia (on the clinical level) most common in Africans/African Americans 1 in 12 black people are carriers causes red blood cells to form sickle shape sickled cells block blood flow symptoms: shortness of breath, pain in joints, anemia, fatigue being a carrier is an advantage against malaria

– alleles: A = normal S = sickle cell genotypes/phenotypes: AA = _________________ (no sickling) AS = _________________ (few cells will sickle; extremely mild symptoms) SS = _________________ (distinct sickling; full-fledged symptoms) normal carrier sickle cell anemia

Problem: 2 carriers have a child. What is the chance that the child will have SCA? _______ X _______ % chance ______ AS 25%

2.Codominance – both phenotypes of homozygous individuals show up in heterozygous -Results in the expression of both traits -Example: chickens

alleles: B = black W = white genotypes/phenotypes: BB = __________ WW = _________ BW = __________ black white checkered

Problem: Cross 2 checkered chickens. What % of the offspring will be white? _______ X _______ ___ of 4 is white = ______% white BW 1 25

Another Codominance Example Roan cow – result of cross between a red cow and a white cow

3.Multiple alleles – there are more than two forms (alleles) for the trait Human example: ABO blood typing alleles: I A, I B, i I A and I B are codominant to each other I A and I B are dominant to __i__ genotypes/phenotypes: I A I A and I A i = _______________ I B I B and I B i = _____________ I A I B = ____________ ii = ___________ type A blood type B blood type AB blood type O blood

Importance of blood typing: parentage blood transfusions incompatible blood can result in blood clotting, then death

Problem: A woman with blood type O has a baby with blood type O. Her husband has blood type AB. Could the baby be his?

Problem: A woman with blood type A has a baby with blood type O. Her husband has blood type B. Could the baby be his?

Transfusion compatibility: A and B are surface proteins on red blood cells You CANNOT accept blood from someone who has a protein that you do not have! DonorDonor ABABO A B O Acceptor

Rh factor – another surface protein _+_ = has Rh protein _-_ = does not have Rh protein (-) can give to (+) (+) cannot give to (-) So, O- can give blood to anyone = universal donor AB+ can get blood from anyone = universal acceptor

If a woman is Rh - and is pregnant with a baby who is Rh +, her body can attack her next Rh+ child. Problem for 2 nd child!!

Test for Blood Typing

4.Sex Determination Humans have 22 pairs of autosomes (chromosomes shared by males and females) and 1 pair of sex chromosomes (X and Y) = __23__ pairs = __46__ total per cell. Humans: XX = female XY = male

Problem: – A man and a woman have 5 sons. What is the chance their next child will be a girl? ALWAYS __50%__ chance!!! FYI: The man “chooses” the sex of the child. Women only have X’s to give. Man gives X to daughters and Y to sons.

5.Sex-Linked Traits/Diseases – controlled by genes on the X or Y chromosomes If trait is on: – X and is dominant – more females have it (ex. scoliosis) – X and is recessive – more males have it (ex. baldness, colorblindness, hemophilia) – Y – only males have it

Red-green colorblindness (recessive on X) N =______________n = _______________ X N X N = ___________X n X n = ___________ X N X n = ___________X n Y = ___________ X N Y = ___________ normalcolorblind female male normal carrier colorblind

A man who is not colorblind has a son with a woman who is a carrier for colorblindness. What is the chance that the son will be colorblind? Who did the son inherit the colorblindness from? Can a man that is not colorblind have a daughter that is?

Hemophilia – disease that interferes with blood clotting Treated with clotting enzymes or transfusion Recessive on X

Famous People with Hemophilia Ryan White and mom Albert and Victoria – English royal family Romanoff Family

N = ____________n = _____________ X N X N = ___________X n X n = ____________ X N X n = ___________X n Y = ____________ X N Y = ___________ A woman who is a carrier for hemophilia and a man who has hemophilia want to have a child. They want to know the chance of their child having hemophilia. normalhemophilia female male normal carrier hemophilia

Sex-Linked Recessive Pedigrees Males have it; females are carriers

6.Polygenic Traits – traits controlled by many genes; difficult to predict exact outcome These traits show broad range of phenotypes Ex. hair color, eye color, skin color, human height