HUMAN GENETICS Humans are not pea plants Although

Humans are not pea plants! • Although in all organisms genes control the production

Can you roll your tongue? • Tongue rolling is determined by a gene with

Set up the problem • R= roller • r=non roller • Both parents are

Here’s an interesting one…. • POLYDACTYLY-having 6 fingers on one or both hands or

Polydactyly is a dominant allele • You cannot pass along alleles you do not

Some human genetic diseases • Show simple recessive heredity, such as cystic fibrosis. •

Tay-Sachs and Phenylketonuria • Are also serious disorders. • Some of these defective genes

Some human inheritance is simple dominant • Such as hitchhiker’s thumb. Does anyone in

NEXT-when inheritance doesn’t follow simple rules-

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HUMAN GENETICS

Humans are not pea plants! • Although in all organisms genes control the production of proteins that show up on our phenotype, most human genetics cannot be explained by tall/short, pink/white, round/wrinkled. • There a few human traits determine by a gene with two alleles, one recessive and one dominant.

Can you roll your tongue? • Tongue rolling is determined by a gene with two alleles, the dominant roller and the recessive non-roller. • If two rollers give birth to a non-roller, what is the genotype of each?

Set up the problem • R= roller • r=non roller • Both parents are rollers, • • R R RR ? R? so they must both have at R? rr=nonleast one R ? roller The offspring shows the recessive trait, so it must be homozygous So, each of the parents must recessive= rr carry the recessive allele. That means they are both R? x R? heterozygous for tongue-rolling.

Here’s an interesting one…. • POLYDACTYLY-having 6 fingers on one or both hands or feet. • The dominant allele is six fingers, showing dominant doesn’t always mean “better” or “most common”. • What’s the chance a child will have polydactyly if both parents have 5 fingers?

Polydactyly is a dominant allele • You cannot pass along alleles you do not have. • If both parents have 5 fingers, they have no allele for 6 fingers, so they cannot pass on the six-fingered allele • 0% chance of 6 fingered children

Some human genetic diseases • Show simple recessive heredity, such as cystic fibrosis. • Cystic fibrosis results from a defective gene that produces a defective protein, accumulating thick mucus in lungs. • If a child is born with cystic fibrosis from parents without the disease, what are the chances his sister will have the disease?

Tay-Sachs and Phenylketonuria • Are also serious disorders. • Some of these defective genes have been located. • Since some genetic disorders run in certain ethnic groups, some people may choose to be tested for the defective gene before they have children.

Some human inheritance is simple dominant • Such as hitchhiker’s thumb. Does anyone in your family have that? • Huntington’s’- a fatal disease caused by a dominant gene, but the gene persists in our population. Why? • Symptoms don’t usually appear until after age 40.

NEXT-when inheritance doesn’t follow simple rules-