Biology: Cell Reproduction (Ch.8) Section Review – Flashcards
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Name the proteins that DNA wraps around to form a chromosome in eukaryotic cells.
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The proteins that DNA wraps around are called histones.
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How do the structure and location of a prokaryotic chromosome differ from that of a eukaryotic chromosome?
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A prokaryotic chromosome is circular and is attached to the inside of the cell membrane. Eukaryotic chromosomes are rod-shaped, have histones and nonhistone proteins, and are found in the nucleus.
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Does chromosome number indicate whether an organism is a plant or an animal? Explain.
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No, the chromosome number does not indicate whether an organism is a plant or an animal because sometimes plants and animals share the same chromosome number.
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Contrast sex chromosomes with autosomes.
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Sex chromosomes determine the sex of an organism while the autosomes contain genes for everything but sex determination.
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Is there a correlation between the number of chromosomes and the complexity of an organism? Give support for your answer.
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No, there is no correlation between the number of chromosomes and the complexity of an organism because an Adder's tongue fern has 1,262 chromosomes while an orangutan has 48 and a human has 46. Animals are more complex organisms than plants.
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What would be the consequence for future generations of cells if sperm and egg cells were normally diploid?
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There would be twice as many chromosomes for each generation.
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What is the sex of the person whose chromosomes are shown in Figure 8-3 above? Explain the answer
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The sex of the person whose chromosomes are shown is male because he has both an X and Y chromosome.
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Name the process by which prokaryotic cells divide.
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Prokaryotic cells divide by binary fission.
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What is the name of the process by which the cell's cytoplasm divides?
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The cell's cytoplasm divides by cytokinesis.
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During which of the phases of interphase does an offspring cell grow to mature size?
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An offspring cell grows to mature size in the G1 phase of interphase.
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During which phase of mitosis do chromatids separate to become chromosomes?
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Chromatids separate to become chromosomes in anaphase.
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Explain the main difference between cytokinesis in animal cells and cytokinesis in plant cells.
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In animal cells, cytokinesis begins with the cell membrane pinching inward between the cell's two poles. This creates a cleavage furrow, which separates and divides the cell into two new cells. In plant cells, vesicles join together at the dividing cell's midline to form a cell plate, which eventually becomes a cell wall and divides the cell into two new cells.
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Which type of molecule controls the cell cycle?
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The cell cycle is controlled by proteins.
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What would happen if cytokinesis took place before mitosis?
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The chromosomes would be divided ineffectively, which could lead to a defective cell.
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What would result if chromosomes did not replicate during interphase?
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If chromosomes did not replicate during interphase, the new cells would have only half the information they need to function properly.
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Why are individual chromosomes more difficult to see during interphase than during mitosis?
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Individual chromosomes are more difficult to see during interphase because they are not tightly coiled and condensed. During mitosis they are tightly coiled, making them easier to see.
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How do the end products of meiosis differ from the end products of mitosis?
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Meiosis produces four haploid cells, and mitosis produces two diploid cells.
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How does anaphase I in meiosis differ from anaphase in mitosis?
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In anaphase I of mitosis, sister chromatids separate. In anaphase I of meiosis, homologous pairs separate, but sister chromatids do not.
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Explain the role of crossing-over in ensuring genetic variation.
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Crossing-over allows genetic material to be exchanged between maternal and paternal chromosomes, producing a new combination of genes.
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During which stage of meiosis is the diploid number of chromosomes reduced to the haploid number of chromosomes?
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telophase I
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Describe the difference between spermatogenesis and oogenesis.
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Spermatogenesis produces four sperm cells with equal parts of the original cell's cytoplasm. Oogenesis produces one egg cell with most of the original cell's cytoplasm, and three other cells become polar bodies that will eventually degenerate.
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Why is meiosis essential to sexual reproduction?
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Meiosis ensures that the chromosome number in a zygote will not be doubled at fertilization. In addition, the resulting offspring are genetically different from either parent.
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Explain why the chromosomes in the haploid cells that are produced by meiosis I look different from those produced by meiosis II.
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Sister chromatids are still together at the end of meiosis I. During meiosis II the sister chromatids separate, forming "single" chromosomes.
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Explain how it might happen that a human offspring with 47 chromosomes could be produced.
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If a gamete with 24 chromosomes fertilized (or was fertilized by) one with the normal 23, the zygote would have 47.
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In humans, the egg is larger than the sperm. Explain how it is possible that a child inherits equally from its mother and father.
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The difference in size is due to the egg gaining the majority of the original cell's cytoplasm, and the sperm getting 1/4 of the cytoplasm. Hereditary is carried primarily in the DNA which is not the same as the cytoplasm.
