Structural comparison of the genome components of eukaryotes
Structural comparison of the genome Structural comparison of the genome
components of prokaryotes components of viruses
Are we prisoners of our DNA? Is DNAour destiny? Nurture Nature Debate
A model of determination that
emphasizes the role of genes A model of determination that emphasizes the role of the environment
ex: queen bee vs worker bee → queen got “royal jelly”
A model of determination that emphasizes the interaction of genes and environment
What genes? What environment? What time?
→ Eg. Heat shock on Drosophila wing development:
eye development: timing is crucial, can only develop during certain windows of devlopment
Q: Do identical twins have the same fingerprints?
Random events in development lead to variation in phenotype called developmental noise.
• have identical genotypes
• but at cellular level, almost impossible to create same environment
• ex: right thumb and left thumb of same person
Not all mutations are equal!
• allele: one of many variants of a gene
◦ Variant meaning mutation
• simplest mutation is a base pair change: eg, G-C toA-T
• others include: single bp insertion, small deletion, large deletions, inversions etc.
• need to ask: Where in the gene? How does it alter the gene products? The nature of alleles and their products
• phenylketonuria (PKU)
◦ symptoms: discoloured urine, mental retardations
• recessive disease is cause by a defective allele of the gene that encodes a liver enzyme called
phenylalanine hdroxylase (p)
Tyrosine: NOT essential
• phenylpyruvic acid interferes with the development of the nervous system (brain) leading to
• can we come up with a treatment?—there are potentially 4
◦ remove phenylalanine from diet
◦ gene therapy: gen for phenylalanine hydroxylase
◦ give phenylalanine hydroxylase
◦ drug/enzyme that breaks down phenylpyruvic acid
◦ block pathways that makes phenylpyruvic acid
◦ full liver transplant
• babies born with phenylalanine hydroxylase (PAH) mutations are not prisoners of their DNA
• changing their diet. i.e lower phenylalanine intake leads to less phenylpyruvic acid by-product
and therefore normal brain development
• when you diagnose and treat is important. why?
◦ earlier the better: developmental windows
• what can you predict about the colour of their skin?
◦ lighter: tyrosine converted into melanin (pigment)
Mutant sites in the PKU gene (phenylalanine hydroxylase ) Gene sites sensitive to mutation
a lot of promoter mutations not affected, b