Answer the following questions in essay form using the information from the image below. 1. Are the chromosomes in the child consistent with those expected in a case of cri-du-chat syndrome? Explain your reasoning. 2. Which parent has an abnormal karyotype? How can you tell? What is the nature of the abnormality? 3. Why does this parent have a normal phenotype? 4. Diagram the pairing of the abnormal chromosomes. 5. What segregation pattern occurred to produce the gamete involved in fertilization of the child with cri-du-chat syndrome? 6. What is the approximate probability that the next child of this couple will have cri-du-chat syndrome? 7. Do the karyotypes of the parents help explain the occurrence of the three previous spontaneous abortions? Explain. 30. Human chromosome 5 and the corresponding chromosomes from chimpanzee, gorilla, and orangutan are shown here. Describe any structural differences you see in the other primate chromosomes in relation to the human chromosome.
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Cri-du-chat syndrome is caused by a deletion of the distal portion of the short arm of chromosome 5 (5p). If the child's karyotype shows such a deletion, it would be consistent with the diagnosis of cri-du-chat syndrome. Show more…
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How do we know? 1. In this chapter, we have focused on chromosomal mutations resulting from a change in number or arrangement of chromosomes. In our discussions, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions? (a) How do we know that the extra chromosome causing Down syndrome is usually maternal in origin? (b) How do we know that human aneuploidy for each of the 22 autosomes occurs at conception, even though most often human aneuploids do not survive embryonic or fetal development and thus are never observed at birth? (c) How do we know that specific mutant phenotypes are due to changes in chromosome number or structure? (d) How do we know that the mutant Bar-eye phenotype in Drosophila is due to a duplicated gene region rather than a change in the nucleotide sequence of a gene? CONCEPT QUESTION 2. Review the Chapter Concepts list on page 188. These all center around chromosome aberrations that create variations from the "normal" diploid genome. Write a short essay that discusses five altered phenotypes that result from specific chromosomal aberrations. 3. Define these pairs of terms, and distinguish between them. aneuploidy/euploidy monosomy/trisomy
Sri K.
Tools of Genetics Part 4: Karyotype (5pt) When cells are dividing during Mitosis, the chromosomes can be photographed and then sorted by size and arranged in homologous pairs, This arrangement is known as a Karyotype. Humans inherit 23 chromosomes from each parent in the gametes, egg and sperm, to total 46 chromosomes in each human cell. Karyotypes provide visual evidence that a developing fetus has the correct total number of chromosomes and that each chromosome present is structurally correct. In some cases we have visible evidence, known as markers, to identify the presence of a gene causing a genetic disorder. Karyotypes can also be used to determine the gender of an individual by looking at the last pair of homologous chromosomes. If the two chromosomes are identical in size then they referred to as two "X" chromosomes and it is a girl. If the two chromosomes are different in size, one larger and one smaller, then the chromosome pair is referred to as "XY" and the gender is identified as male. These chromosomes are not the only factors that genetically determine all of the qualities of gender and we continue to learn more as our technology progresses.
Dominador T.
After reading the paragraphs below, answer the questions that follow. Mr. and Mrs. Smith have three sons in elementary school. Two of their children are progressing normally, but their youngest son, Charles, has been much slower than his siblings in developing speech and language skills. His parents are concerned that he has a learning disability and decide to investigate further. Since some learning disabilities can be genetically based, their pediatrician recommends a chromosomal analysis. The results show that Charles has a trisomy of the sex chromosomes, diagnosed as XYY, which is caused by nondisjunction in the formation of the father's sperm. The nondisjunction resulted in an extra copy of the Y chromosome. The extra copy was passed on to Charles during fertilization. Most often, this chromosomal change causes no unusual physical features or medical problems, but those with the trisomy of the sex chromosomes do have a higher than normal risk of delays in learning development. 1. During which stage of meiosis could this nondisjunction have occurred? a. telophase I b. prophase I c. anaphase II d. telophase II 2. If Charles gets married and starts a family, which of the following chromosomal abnormalities has an increased chance of occurring in his children? a. YO b. YY c. XO d. XXY
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