During Meiosis I, chromosomes undergo a _____ forming a _____ cross over, dyad s
ID: 179377 • Letter: D
Question
During Meiosis I, chromosomes undergo a _____ forming a _____ cross over, dyad synapsis; tetrad fertilization; zygote switch over, tetrad none of the above When one sperm nucleus fuses with the ovum and another sperm nucleus fuses with two polar bodies this process is called ____. Triple fertilization Quadruple fertilization Fusion Double fertilization None of the above When mating flies, virgin females are distinguished by their _____. Pointed bottoms, sex combs Colorless under belly, dark spot Round bottom, sex combs Colored body, darks spots None of the above The term ____ is always applied to a chromosome with an intact centromere. Inversion Translocation Pericentric Paracentric DerivativeExplanation / Answer
1. A tetrad refers to the entire group of four chromosomes after they have come together for crossing over in prophase I of meiosis I. Synapsis refers to the process by which themselves tetrads form. Therefore the correct answer is (b) synapsis, tetrad.
2. In triple fertilization, one sperm nuclei fuses with the egg and forms a zygote and the other fuses with two polar nuclei of the central cell and forms a triple fusion or endosperm. In double fertilization a female gametophyte fuses with two male gametes. So, the answer is (A). Triple fertilization.
3. Virgin females flies have several defining characteristics that separate them from mated females :
- very pale,
- dark spot seen in abdomen,
- distended, large abdomen.
Therefore, (B) is the right option.
4. A derivative chromosome is structurally rearranged chromosome generated by a rearrangement involving two or more chromosomes or by multiple aberrations within a single chromosome. This term is always refers to the chromosome that has an intact centromere. The option (E) is the right option.
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