A. We are constantly being tested (from birth). 1) Why? Test newborns to check for congenital health problems. 2) What does congenital mean?

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1 M 109 Introduction I. PKU illustrates the relevance of chemistry to human health Why is chemistry important in human health? Ex.: PKU (phenylketonuria) ref. Matalon, KM Top lin Nutr 16(4):41-50 (2001) A. We are constantly being tested (from birth). 1) Why? Test newborns to check for congenital health problems. 2) What does congenital mean? B. What is PKU? A genetic disease caused by insufficient phenylalanine hydroxylase (PA) activity. PA phenylalanine + oxidant tyrosine 2 O O N + 3 N 1) PA rxn.: 2) PA is an enzyme. (means? ) 3) The PA of PKU patients is absent or doesn t work as well as normal PA because its structure is different from normal, wild type (means? ), PA. This is 1 of ~ 10 4 jobs you must do to stay alive, healthy.. Why does lack of PA activity cause problems in PKU? O 2 O O - 1) Phenylalanine (Phe) levels increase. Some of this Phe is converted to phenylketones (excreted in urine). PA phenylalanine + oxidant tyrosine phenyketones 2) Part of the PKU pathology (means? ) appears to be caused by elevated Phe. ow Phe does this is not completely clear, (ex. :see Shefer, et al., J Neurosci Res. 61(5): , 2000). 1

2 3) Tyrosine (Tyr) is not formed via the PA pathway in PKU patients, so Tyr is an essential amino acid for them (dietary supplements needed!). D. Back to Why test newborns? PKU can be treated! See: Irene, spouse, sister, (& Stephanie) (Pheno, Genotypes?) This photo was taken at my wedding a few years ago. I have PKU. I was diagnosed on the 3rd day of my life when treatment with the diet began.... The other woman in the picture is my older sister. She also has PKU but when she was born there was no newborn screening program for PKU. The diagnosis of her disease was made late in her first year of life when she developed convulsions. It was too late for treatment and she has never known the benefits of early diagnosis and treatment as I know them...(irene, May 1998) Note: The pictures at right and above are from The Montreal hildren s ospital yperphenylalaninemia (PKU) Resource Booklet for Families, by Peter M. Nowacki at The Biochemical Genetics Unit; updated by Annie apua, Margaret Lilly, David é, Manyphong Phommarinh and Shannon Ryan. Used with permission, Dr.. Scriver. 1. Set diet with low levels of Phe 2. Supplement w/ Tyr, which leads to healthy Irene & eventually to healthy 2 yr old Stephanie, þ 2

3 E. What happens to PKU patients that are not treated or are not compliant with their treatment? i.e., What is the pathology? See Irene s sister, above. 1. Mental retardation 2. Microencephaly (means? ) 3. ongenital heart disease F. Genetics Loss of function genetic diseases & diploidy. 1. Genotype vs. phenotype (Look up if unfamiliar.) genotype phenotype 2. What can you say re. genes of parents of a PKU patient? Nice web site (from McGill Univ.) with lots of information about specific PKU mutations: also see: G. The PA gene is complex. It can go wrong, in many ways. (See figs & mutation map on following pages.) Remember major theme for this course: DNA ö RNA ö Protein. uman haploid genome, chromosome 12, PA gene The uman Genome Project 3

4 2. Now search PKU It turns out that the gene that codes for PA is on chromosome # Gene: a linear sequence of bases in DNA that codes (information) for a specific function (job). Based on: PA gene expression Dr.. Scriver, uman Mutation 28(9): (2007). DNA PA gene is 171,266 base pairs long RNA Mature PA mrna is 4,932 bases long Protein PA protein subunit is 452 amino acids long 4,932 is ~ 2.9% of 171,266! Why have the extra 97%? 4

5 Aside: It will be easier to understand if we relate the above processes to where they occur in a cell: What other kind of nucleus should you be able to draw? 4. The thin verticle lines in the mutation map (see link) ( are put together to form the mature mrna (short for? ). The open blocks labeled 1-12 are spliced out and degraded. 5. View the PA gene like a paper you have written that has 171, 266 letters. (Spelling errors possible?). Spelling error. a mutation (sequence change). a) learly a spelling error could result in less effective communication. (like a harmful mutation) b) an you imagine a spelling error resulting in more effective communication. (a helpful mutation?) different mutations ( )! See map on PAdb website, Dr.. Scriver. 5

6 I. If we understand, structure tells us about function and helps develop treatments. 1. The structure of DNA: a double helix (this piece is only 20 bp long!) Spac e-filling model wireframe model ribbon model 2. Don t worry about RNA structure for now. 3. Structure of the protein PA (from PDB structure 1PA. ydrogen atoms are not shown. Object here is not to memorize atom locations.) Space-filling model, PK atom coloring Ribbon model. α-helices: red, β-sheets: yellow 6