Unequal crossing over often results in the formation of duplicate copies of existing genes. At what phase of meiosis can unequal crossing over occur, and why does this happen?
What will be an ideal response?
Unequal crossing over occurs during prophase of meiosis I, and occurs when homologous chromosomes line up incorrectly.
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Plants are able to defend themselves against viruses that have invaded their cells by:
A. producing antibodies. B. recognizing and interrupting viral RNA replication. C. causing the virus to detach from the cell membrane before it injects its RNA. D. producing sticky proteins on the cell surface that capture the viruses. E. increasing the number of plasmodesmata per cell.
The sheaths that surround neurons are composed of
a. amino acids. b. lipids. c. cholesterol. d. carbohydrates e. polysaccharides.
During the first 5–600 million years on Earth, temperatures ranged from 500–1000°C, atmospheric pressure was 10 times current levels, and the planet was bombarded with meteorites. How would these conditions favor the formation of biological molecules?
A. Many chemical reactions are inhibited by high temperature and pressure. B. High temperature and pressure are the best conditions for enzyme function, needed to support life. C. Oxygen will break down many organic molecules by reduction. D. Oxygen in this high temperature and pressure atmosphere would have been chemically less reactive. E. Water and meteorite dust would have provided the chemical reactions necessary for formation of biological molecules.
. Killifish and pike-cichlids raised in natural
conditions will
a. control the size of the guppies that live with them. b. function as predators to guppies. c. determine the growth rate of guppies. d. control the evolution of size and color of the guppies. e. do all of these.