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Pedigrees Genetics Review of Crosses Parents Offspring AA x AA AA x Aa AA x aa Aa x Aa Aa x aa aa x aa all AA 1/2 AA:1/2 Aa all Aa 1/4 AA:1/2 Aa:1/4 aa 1/2 Aa:1/2 aa all aa Probability • Likelihood of an event occurring • What is likelihood of heads when coin is flipped? •What is likelihood of a 1 when die is rolled? possibility of one outcome •Probability = number of outcomes Genetics Cross • In humans, widow’s peak is dominant to straight hairline. If two parents Ww x ww What is the chance child will have widow’s peak? W w w Ww ww w Ww ww Two Events What is the probability of getting heads on both coins? • • H, T • T, H • T,T H, H Product Rule - the probability of 2 independent events occurring simultaneously is the product of their individual probabilities. Two Events What is the probability of getting heads on one coin and tails on the other? • • H, T • T, H • T,T H, H Sum Rule - the probability of either one or the other of two possible events is the sum of the individual probabilities. Genetics Cross • In humans, widow’s peak is dominant to straight hairline. If two parents Ww x ww What is the chance a child will have widow’s peak? What is the chance they will have 2 children with widow’s peak? Their 1st child has w.p. What is chance the second child will have w.p.? Genetic Diseases • In humans, normal is dominant to sickle cell anemia. SS - normal Ss - normal (carrier) ss - sickle cell If two parents Ss x Ss What is the chance a child will have sickle cell? What is the chance a child will be a carrier? Conditional Probability •Probability of an event in which some information is already known •Example: A person rolls a die and gets an odd number, what is the chance it is a 1? Sickle Cell Anemia If two parents Ss x Ss have a normal child S s S SS Ss s Ss ss What is the chance the child is a carrier (Ss)? Pedigree • Diagram of family relationships showing genetic traits male female mating I 1 2 II offspring 1 2 mating relatives 3 twins identical • I II III Albinism Pedigree AA normal Aa normal (carrier) aa albino Deafness Pedigree • I II III DD and Dd deaf dd normal Compare Pedigrees albinism - recessive disease Aa deafness - dominant disease dd aa Aa aa aa Aa Aa Aa Aa Aa •disease not common •may skip generation •unaffected parents can have affected offspring AA Dd dd Dd dd dd dd Dd dd dd Dd dd dd •disease common •never skips generation •2 affected parents can have normal child Activity 3 Pedigrees
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