What bacteria are important in the human gut and what evidence do we have that specific bacteria present are important for human health?

Generally, blue eyes are recessive to dark brown eyes in humans. Individuals with albinism typically have blue eyes with a strong red reflection. A blue-eyed woman with albinism marries a man who is blue-eyed but does not have albinism

All their children have dark brown eyes. How can this be explained?

The number of similarities in certain DNA or RNA nucleotide or amino acid sequences may be used

as a molecular clock to indicate how much time has passed since the groups branched from a common ancestor. __________________ Indicate whether the statement is true or false.

Interferons and complement proteins are examples of:

A. mechanical barriers B. antibodies (immunoglobulins) C. phagocytes D. chemical barriers

A researcher is interested to test the hypothesis that a 100 base pair stretch of a given gene is under selection

She sequences this gene region in 30 individuals, each of two populations. She finds that within either popula-tion, there are 33 synonymous sites of which 10 are segregating for different alleles in the population. In this same sequence, she observes 29 sites within-populations that possess variable alleles at nonsynonymous sites. In contrast, when she compares substitutions across species, she finds that of the 33 synonymous sites only five show signs of a substitution between species. Only 15 nonsynonymous substitutions were observed between species. This suggests that the gene is: a. under purifying selection. b. under nearly neutral selection. c. under positive selection. d. under directional selection. e. This cannot be determined based on the information provided.