Which of the following statements about stem cells is NOT accurate?
A. Stem cells can undergo mitosis.
B. Some stem cells can differentiate into more than one type of specialized cell.
C. Different types of stem cells vary in their potency.
D. Stem cells are only found in embryos.
E. Some stem cells can only differentiate into one cell type.
D. Stem cells are only found in embryos.
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Cells are often ground up with abrasive to get to their internal enzymes/molecules, followed by removal of the abrasives. Here are three situations and three outcomes. What is the correct interpretation of the results?
In situation #1, radioactive amino acids are added to cell material, and radioactive proteins are produced. In situation #2, radioactive amino acids, cell material, and the enzyme DNAse (degrades DNA) are added together. Radioactive proteins are still produced. In situation #3, the ground-up cell material is allowed to sit for 24 hours before radioactive amino acids and DNAse are added to it. No radioactive protein is produced. What is the most likely interpretation? A. RNA polymerase has no activity after 24 hours, so no mRNA is transcribed and translated into radioactive proteinsin the last scenario. B. The radioactivity in the amino acids is altering/degrading the tRNA molecules, leading to no protein production in the last scenario. C. Natural RNAses present in the ground-up material will degrade any existing mRNAs in that 24-hour interval. Added DNAses breakdown DNA so that new RNAs are not synthesized.This will lead to a loss of capability to translate protein in the last scenario. D. The results are not interpretable from the information given.
Which of the following choices is not a function of astrocytes?
a. engulf dead or dying cells b. assist in immune defense c. stimulate formation of the blood-brain barrier d. take up neurotransmitters
The stages of mitosis plus interphase are listed below with letters a
through e. Select the correct phase for each statement numbered 70–80. a. interphase b. prophase c. metaphase d. anaphase e. telophase E 70. Homologous pairs of chromosomes line up on the equatorial plate. M 71. Chromosomes replicate. M 72. Genes replicate. E 73. DNA replicates. E 74. Condensation and shortening of chromosomes occurs. E 75. Spindle fibers first appear. M 76. Centromeres break apart as the separated sister chromatids begin to move to opposite poles. E 77. The microtubular spindle develops. E 78. Sister chromatids joined at their centromeres are attached to spindle fibers. M 79. Cytokinesis occurs after this phase of mitosis. E 80. Daughter nuclear membranes form.
Which of the following is used in the production of buttermilk and cheese?
A. Streptococcus mutans B. Enterococcus faecalis C. Lactococcus lactis D. Streptococcus pneumoniae