An allele of RNA polymerase in Drosophila demonstrates a recessive lethal inheritance pattern. Which of the following is true?
A) Homozygous lethal genes will always demonstrate a gain of function pattern.
B) The threshold effect is not seen in recessive lethality.
C) Two homozygous recessive parents will have 100% homozygous offspring.
D) Homozygous recessive offspring will never be seen.
E) Two heterozygotes will have offspring with a 2:1 pattern.
Answer: D
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How do modified and unmodified histone subunits become distributed among nucleosomes after replication?
A. The newly synthesized DNA strand contains unmodified histone subunits, while the old strand retains the modified histones. B. Both strands of DNA are repopulated first with a mixture of modified and unmodified H2A histones, followed by mixtures of H2B, H3, and, finally, H4. C. Both strands of DNA are repopulated first with a mixture of modified and unmodified H2A and H2B histones, followed by mixtures of H3 and finally mixtures of H4. D. Both strands of DNA retain H3-H4 modified pairs, and then are repopulated with unmodified H3-H4 pairs, followed by modified and unmodified H2A-H2B. E. Both strands of DNA retain H2A-H2B modified pairs, and are then repopulated with unmodified H2A-H2B pairs and then mixtures of modified and unmodified H3-H4 pairs.
Which type of microscopy transforms the subtle variations in cell density into differences in light intensity, allowing for increased internal detail without staining?
A. Confocal B. Bright-field C. Phase-contrast D. Fluorescence E. Electron
HIV/AIDS is one of the ten top causes of death in the United States.
a. true b. false
A group is considered polyphyletic if
A. all members share homoplastic traits. B. the group does not contain the most recent common ancestor. C. it is the most parsimonious grouping. D. not all descendants of the common ancestor are included. E. all members of the group share a common ancestor.