Worldwide, only about 35% of adults can digest lactose, the primary sugar in milk. Breakdown of lactose requires the enzyme lactase; while it is normal for all mammals to express lactase as an infant, in most species, including humans, the gene is turned off at weaning.  Thus, in most people, consumption of dairy products in adulthood is less than pleasant, a condition termed lactose intolerance.  Lactose intolerance is caused by the non-persistence of lactase expression.  The mutation that led to lactase-persistence (continued expression of lactase) is thought to have risen in frequency in pastoralist populations – those that started domesticating and farming animals.  Lactase persistence (LP) arose independently in both African and European populations.  The African and European populations have different LP mutations, but all LP mutations are in the regulatory region of the lactase gene. . Thus, lactase persistence demonstrates:

Worldwide, only about 35% of adults can digest lactose, the primary sugar in milk. Breakdown of lactose requires the enzyme lactase; while it is normal for all mammals to express lactase as an infant, in most species, including humans, the gene is turned off at weaning.  Thus, in most people, consumption of dairy products in adulthood is less than pleasant, a condition termed lactose intolerance.  Lactose intolerance is caused by the non-persistence of lactase expression.  The mutation that led to lactase-persistence (continued expression of lactase) is thought to have risen in frequency in pastoralist populations – those that started domesticating and farming animals.  The image below shows regions of DNA around the lactase gene in African and European populations.  The lactase persistence allele is shown in red.  Each row is an individual and the colored bars indicate areas of homozygosity – a region where both chromosomes in one person are exactly the same sequence.  These areas of homozygosity represent DNA sequences that are all inherited together without being split apart by recombination.  What is the term for this?    

Remember hilltopperitis = all those affected have blue hair and yellow skin, about 50% of those affected have tiny horns, and the others have very noticeable horns.  You are interested in finding the gene(s) responsible for the horn phenotype; you decide to approach this by using a microarray. You isolate mRNA from tiny horns and large horns. You use the mRNA to create fluorescently labeled cDNA –  blue (tiny) and yellow (large) (blue+yellow = brownish-grey).  You use these samples to probe a human microarray that contains sequences representing ALL human protein coding genes. Explain the rationale for using samples from individuals with tiny horns and large horns.  How will these samples be useful for identifying genes involved in this phenotype? (In other words, if a gene is responsible for the horn phenotype, how will it’s expression be different in individuals with tiny horns and large horns?)

Rewrite the following equations in simplified slope-intercept form (y = mx + b). Remember, don’t leave a 1 in front of a variable. 1. 5x + y = 5  [a]  3 points 2. -4x + 4y = 8  [b]  2 points 3. -14x – 7y = -7 [c]  1 point  

Jamie has $900 in a bank account. She signs up for a one-year cell phone contract that automatically takes $50 from her account each month. The contract only lasts for one-year and Jamie does not use this account for anything else.  Use this story problem to help you answer the questions that follow.

How would an earthworm stretch its body to reach a patch of dirt after crossing a hot sidewalk?

Examples of mollusks that live on land are the

Each segment of an annelid typically contains bristles of chitin called

What would result if a leech had a mutation causing it to secrete low levels of anticoagulants?

Chelicerae function as