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Nondisjunction occurs in too many cells or too few cells causing defects

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What happens in metaphase 1?

pairs of homologous chromosomes move to the equator of the cell


What happens to the chromosomes near the end of the process of mitosis?

Mitosis is the process of cell division in which the chromosomes condense and the spindle is assembled. In each phase the chromosomes do different things: prophase: during this first phase of mitosis, the parent chromosomes become compacted and the spindle begins to form creating an X-shape when looked at through a microscope; prometaphase: the nuclear membrane becomes many small vesicles during this phase. The spindle microtubules reach out until they connect the chromosomes to their kinetochore and then a sort of "tug-of-war" happens while the chromosomes bounce between the two poles; metaphase: the chromosomes align along the equator of the cell as they become connected to the spindle poles; anaphase: the chromosomes work their way into becoming individual/independent chromosomes as they begin to find their place near the poles; and telophase: the chromosomes find their poles, the spindle disbands, and each chromosome gets its new nuclear membrane.


What happens during metaphase in the cell division?

Metaphase is the phase of cell division where chromosomes line up on the equator of the cell just prior to splitting to the poles at anaphase. During mitosis identical chromosomes pair up on the equator, wheras during meiosis the homologous pairs line up together during meiosis 1 and then homologous chromatids line up together in meiosis 2.


What are types of point mutation?

The types of point mutations are: base-pair substitution, insertions, deletions, and frameshift mutations. In base-pair substitution, one nucleotide and its corresponding partner are replaced with another pair of nucleotide. In insertion, nucleotide pairs are added to a gene. In deletion, nucleotide pairs are taken out of a gene. Frameshift mutation happens as a result of insertion or deletion when more or less than three (or a multiple of three) nucleotide pairs are added to or taken from a gene.


During the process of fertilization which step happens first?

It is hard to say which step happens first in the process of human fertilization. The process leading up to it is usually slow. A man and a woman smile at each other. That is actually the first step. They get to know each other. The process goes on and on. A man grabs hold of a woman. Neither one has clothes on. He puts his penis in her vagina. Both push back and forth. Eventually, with them breathing hard, he ejaculates semen. Sperm work their way out from her vagina, through her uterus into her fallopian tubes. Meanwhile, her ovaries prepare an egg. It has a full set of chromosomes. It loses half of them. Unlike ordinarily cell division, only the nucleus divides. The egg cell ejects the nucleus called a polar body. The ovary ejects the egg. little cilia move the egg to the fallopian tubes. There it meets the sperm. The sperm breaks through the surface of the egg. The surface becomes hard so no more sperm will break through. The sperm swims through the egg until it reaches the nucleus. There it deposits its chromosomes. The chromosomes in the nucleus break apart and then reassemble. At that point the chromosomes of the new individual exist in the form the new person will have them the rest of his or her life. Which step happened first?