The concept of developmental constraint may be defined as ________
A) the sudden appearance of new phenotypes
B) homoplasy that results from the same underlying developmental mechanism
C) phenotypic similarity due to descent from a common ancestor
D) a bias toward certain kinds of variation in phenotype
E) the fact that all animals develop using the same "toolkit" of Hox genes
D
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Which of the following molecules is not considered a porphyrin?
A. Hemoglobin B. Peptidoglycan C. Vitamin B12 D. Chlorophyll
In a human male, how many total chromatids are present in cell number 4?
a. 2 b. 4 c. 23 d. 46 e. 92
Cellulose belongs to which of the following groups of macromolecules?
A) lipids B) carbohydrates C) proteins D) nucleic acids E) none of these
In later chapters, you will learn more about the regulation of gene expression. One way to regulate gene expression is to make changes to the histone proteins to alter how tightly the DNA is coiled and wrapped. The more tightly coiled and wrapped a particular region of DNA is, the less likely it is that the genes in that region will be expressed. Bearing this in mind, how tightly do you think regions of heterochromatin are compacted?
A. Loosely B. Moderately C. Very tightly D. Not at all