3_BIOL1510-Module+4-Lecture+3+Genetics+Sakai

3_BIOL1510-Module+4-Lecture+3+Genetics+Sakai - Module 4:...

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Unformatted text preview: Module 4: Genetics Lecture 2 How does chromosomal alignment (karyotypes) inform diagnoses? How are single-gene traits inherited? How did Mendel use monohybrid and dihybrid crosses to demonstrate the laws of inheritance? Phenylketonuria (PKU) All newborns in the United States are screened at birth for a mutation that causes a deficiency in the enzyme phenylalanine hydroxylase (PAH) , necessary to metabolize phenylalanine to tyrosine*. When PAH is deficient, phenylalanine accumulates and is converted into phenylketone, which is detected in the urine. The PAH gene is found on chromosome 12. Over 100 different mutant forms of this gene can cause PKU. How would a baby get PKU? *tyrosine is conditionally-essential, meaning that we can synthesize it if we have sufficient phenylalanine PAH Punnett squares provide the possible offspring types given the parents genotypes R r R r Genotype: Rr Phenotype: Unaffected Carrier Genotype: Rr Phenotype: Unaffected Carrier R r R r Q: What are the chances of two carrier parents having a carrier baby? a) 0 b) 0.25 c) 0.5 d) 0.75 e) 1.0 1/2 1/2 1/2 1/2 R r R r Which of the four possible offspring types are homozygotes? a b c d) a and c. e) None of these is a homozygote. Allele 1 Allele 2 homozygous: alleles are the same heterozygous: alleles differ recessive: allele masked in heterozygous state dominant: allele fully expressed in heterozygous state If Mom were phenylketonuric and Dad a carrier, what types of offspring would you predict? a) 50% carriers & 50% PKU sons b) 50% carriers & 50% PKU daughters c) PKU sons and carrier daughters d) All carriers or normal. e) a and b. Q: Phenylketonuria is an example of which kind of heritable disease? a) Autosomal recessive, like albinism b) Autosomal dominant, like Huntingtons disease c) X-linked recessive such as Color-blindness d) X-linked dominant such as Rett syndrome e) Y-linked recessive Parental Second filial First filial Law of segregation Two alleles separate to end up in different gametes Law of independent assortment At each locus, each pair of alleles separates independently of each other pair of alleles during gamete formation Chr. 4 Chr. 12 If a man with HD and PKU and...
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This note was uploaded on 05/01/2011 for the course BIOL 1510 taught by Professor Jungh.choi during the Spring '07 term at Georgia Institute of Technology.

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3_BIOL1510-Module+4-Lecture+3+Genetics+Sakai - Module 4:...

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