phenotype (observable characteristics). B. The Genetic Code 1. Chromosomes store and transmit genetic information. Each cell in the human body contains 23 pairs of chromosomes. 2. DNA (deoxyribonucleic acid) molecules make up chromosomes. 3. A gene is a segment of a DNA molecule which contains instructions for making proteins. 4. Mitosis is the process of cell duplication in which each new cell receives an exact copy of the original chromosomes. C. The Sex Cells 1. Sex cells‚ also known as gametes‚ are
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represents nature’s solution to the problem of chromosome doubling that would occur‚ if two diploid cells‚ i.e. two cells with a double set of chromosomes would fuse. Accordingly does meiosis produce haploid germ cells‚ with maternal and paternal germ cell fusing at fertilization and thus generating a diploid fusion product‚ the zygote. Meiosis is made up by two subsequent processes‚ both of which resemble mitosis. In the first process are the homologous chromosomes separated. It has an unusually long prophase
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Question If a cell contains a set of duplicated chromosomes‚ does it contain any more genetic information than the cell before the chromosomes were duplicated? No‚ because if it is duplicated‚ it would have the same number of chromosomes unless there was a mistake. Why do chromosomes condense before they are moved? Chromosomes condense because it allows them the ability to move smoothly‚ without becoming entangled and breaking. How are the chromosomes copies‚ called sister chromatids‚ separated
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heart‚ endocrine system‚ and central nervous system. It can be classified into two types: DM1 and DM2‚ also known as Proximal Myotonic Myopathia (PROMM). DM1 is caused by a continuous repeat of CTG located on chromosome 19‚ while DM2 is caused by the expanded quadruplet of CCTG on chromosome 3. They are both inherited as autosomal dominant trait‚ differing only by the characteristic of DM2 that contains one or more ion-channel defects. The second type of myotonic dystrophy is rarely found; therefore
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copied chromosomes are separated into two new nuclei. Then in cytokinesis the cell divides into two daughter cells. If no mutations or errors occur‚ the genetic material in each daughter cell is identical to what was in the original cell. Now that you have completed this lesson‚ you should be able to: describe the stages of the cell cycle explain the process of mitosis and its role in the formation of new cells describe the structure of a chromosome follow chromosomes through
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DIRE C T ION S: Answer the following math problems. Use the space below each problem or a separate piece of paper to show your work. 1. 1201 OOD Answer: ’1000j of) rbe- 1000 A typical human-body cell has 46 chromosomes. If half of them come from each parent‚ how many chromosomes does each parent contribute? Answer: ;)3 C\lvorno5(-J/u.W x 000 GO see.‚ ( see 2. 4. The red bone marrow in a human’s bones produces about 2‚000‚000 red blood cells every second. How many red blood cells are
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which one or more chromosomes are present in extra copies or are deficient in number. 2.barr body: a dense object lying along the inside of the nuclear envelope in female mammalian cells‚ representing an inactivated X chromosome. 3.chromosome theory of inheritance: generalization that genes are located on chromosomes and that the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns 4.crossing over: process in which homologous chromosomes exchange portions
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(replicates) DNA in preparation for division. The G1 phase‚ also called Gap 1‚ is the first phase of interphase. During G1‚ the cell increases in size. The S phase‚ also called the synthesis phase‚ follows G1. During S phase‚ the cell synthesizes DNA. Each chromosome is now comprised of two identical sister chromatids as a result of DNA synthesis. The G2 phase‚ also called Gap 2‚ follows the S phase. During G2‚ the cell once again increases in size and produces proteins necessary for Mitosis. After G2‚ the cell
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female-sterility factors. There should not be any recombination between different loci which is the pivotal reason for the genetic degeneration of Y chromosomes. There are several theories attached to Y chromosome degeneration that are reviewed recently . Introduction: why are plant sex chromosomes of particular interest? Sex inheritance and sex chromosomes in plants are similar to those in animals. In many sexually reproducing plant species all individuals are ’sexually monomorphic’ or hermaphroditic
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German biologist Oscar Hertwig. It was described again in 1883‚ at the level of chromosomes‚ by the Belgian zoologist Edouard Van Beneden‚ in Ascaris worms’ eggs. The significance of meiosis for reproduction and inheritance‚ however‚ was described only in 1890 by German biologist August Weismann‚ who noted that two cell divisions were necessary to transform one diploid cell into four haploid cells if the number of chromosomes had to be maintained. In 1911 the American geneticist Thomas Hunt Morgan observed
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