Human Biology Custom Edition
11th Edition
ISBN: 9781337631532
Author: Cecie Starr, Beverly McMillan
Publisher: Cengage Learning
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Chapter 20, Problem 3CT
People with Down syndrome have an extra copy of chromosome 21, for a total of 47 chromosomes. However, in a few cases of Down syndrome, 46 chromosomes are present. This total includes two normal-looking chromosomes 21, one normal chromosome 14, and a longer-than-normal chromosome 14. Interpret this observation. How can these individuals have 46 chromosomes?
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"If a fragment of a chromosome breaks off and then reattaches to the original chromosome but in the reverse direction, the resulting chromosomal abnormality is called a translocation."
The above statement is True or False? and Explain
In a sample of 1000 patients with Down syndrome, a geneticist discovers that 95% of them are trisomic, while 5% have diploid number of chromosomes. Explain this discrepancy.
Two phenotypically normal parents produce a phenotypically abnormal child in which chromosome 5 is missing part of its long arm but has a piece of chromosome 7 attached to it. The child also has one normal copy of chromosome 5 and two normal copies of chromosome 7. With regard to chromosomes 5 and 7, what do you think are the chromosomal compositions of the parents?
Would it most likely be reciprocal translocation? It wouldn't be simple translocation because then the child would have the entirety of one chromosome and only some of the other, but in this case, there is only partial chromosome 5 and chromosome 7?
Chapter 20 Solutions
Human Biology Custom Edition
Ch. 20 - Prob. 1RQCh. 20 - What is a carrier of a genetic trait?Ch. 20 - What evidence indicates that a trait is coded by a...Ch. 20 - Prob. 4RQCh. 20 - Explain what nondisjunction is, and give two...Ch. 20 - _______ segregate during ______. a. Homologues;...Ch. 20 - Prob. 2SQCh. 20 - Genes on the same chromosome tend to stay together...Ch. 20 - Prob. 4SQCh. 20 - A chromosomes structure can be altered by _______....
Ch. 20 - Nondisjunction can be caused by ________. a....Ch. 20 - A gamete affected by nondisjunction could have...Ch. 20 - Genetic disorders can be caused by __________. a....Ch. 20 - A person who is a carrier for a genetic trait...Ch. 20 - Prob. 10SQCh. 20 - If a couple has six boys, what is the probability...Ch. 20 - Human sex chromosomes are XX for females and XY...Ch. 20 - People with Down syndrome have an extra copy of...Ch. 20 - Prob. 4CTCh. 20 - Prob. 5CTCh. 20 - About 4 percent of people of Northern European...Ch. 20 - The following pedigree shows the pattern of...
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- A girl and a boy were born to a young married couple. The girl is absolutely healthy. The examination of the boy's karyotype has shown 46 chromosomes. But one of the chromosomes of the 15th pair is longer than normal as a part of a chromosome from the 21st pair has joined it. How many autosomes and sex chromosomes are in the boy's karyotype? Name the type of the mutation. Is it possible to consider this pathology an inherited disorder?arrow_forwardIn humans, chromosome 16 sometimes has a heavily stained area in the long arm near the centromere. This feature can be seen through the microscope but has no effect on the phenotype of the person carrying it. When such a “blob” exists on a particular copy of chromosome 16, it is a constant feature of that chromosome and is inherited. A couple conceived a child, but the fetus had multiple abnormalities and was miscarried. When the chromosomes of the fetus were studied, it was discovered that it had three copies of chromosome 16 (it was trisomic for chromosome 16), and that two of the three chromosome 16s had large blobs. Both chromosome 16 homologs in the mother lacked blobs, but the father was heterozygous for blobs. Which parent experienced nondisjunction, and in which meiotic division did it occur?arrow_forwardA phenotypically normal woman has an abnormally structured chromosome 2, along with a normal homologue. She marries a phenotypically normal man with an abnormally structured chromosome 16 and a normal homologue. What is the probability of their child will have an abnormal chromosome 2 and 16? What is the probability that this child, having inherited both abnormal chromosomes, will now pass both abnormal chromosomes to its children?arrow_forward
- Familial Down syndrome is similar to primary Down syndrome in that it is caused by trisomy 21. However, in familial Down syndrome, all or part of the third copy of chromosome 21 has translocated onto another autosome, typically chromosome 14. In cases of familial Down syndrome, one of the parents of the affected child is often a carrier of a translocated chromosome. The translocation carrier parent does not have Down syndrome because he or she has a total of two copies of chromosome 21. Suppose that a woman is a translocation carrier of chromosome 21 on chromosome 14. She conceives six zygotes with a man who carries no aneuploidies. Match the description of the chromosomes inherited by each zygote with the viability and phenotype of the zygote. ✓ Two normal copies of 14, two normal copies of 21 two normal copies of 21, one normal copy of 14 ✓one normal copy of 14, one 21 to 14 translocation, one normal copy of 21 ✓two normal copies of 14, one normal copy of 21, on 21 to 14…arrow_forwardFrom 2 to 6 percent of people with autism have an extra chromosome that consists of two long arms of chromosome 15. It includes two copies of the chromosome 15 centromere. Two normal copies of the chromosome are also present. What type of chromosome abnormality in a gamete can lead to this karyotype, which is called isodicentric 15?arrow_forwardIn humans, chromosome 16 sometimes has a heavily stained area near the centromere. This feature can be seen in a microscope, but otherwise has no effect on the phenotype of the person carrying it. When such a “blob" exists on a given copy of chromosome 16, it is a constant feature of that chromosome and is inherited. A couple conceived a child, but the fetus had multiple abnormalities and was miscarried. e.g., The fetus had three copies of chromosome 16, where 2 of the 3 copies of chromosome 16 had large blobs. Both of the mother's copies of chromosome 16 lacked blobs, but the father was heterozygous for blobs. The fetus was formed from a fertilization event that included a gamete produced by the in which nondisjunction occurred during the meiotic division. Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a mother; first. mother; second. father; first. C Your answer d father; second. E3 Fullso L e Insufficient information is provided…arrow_forward
- Why is the incidence of survivable genetic disorders involving deletions of parts of chromosomes so rare? Why is the incidence of trisomy of larger chromosomes rarer than the incidence of trisomy of smaller chromosomes? What is the relationship between the severity of symptoms and the size of chromosome involved in the trisomy?arrow_forwardIn general, why do changes in chromosome structure or numbertend to affect an individual’s phenotype? Explain why somechanges in chromosome structure, such as reciprocal translocations,do not.arrow_forwardwhat is the significance of chromosomal aberration? what are the different types of chromosomal abberations based on the structure and number of chromosomes? give examples for each. what environmental factors may increase in the incidence of chromosomal aberrations?arrow_forward
- A rare form of dwarfism that also includes hearing loss was found to run in a particular family. It is inherited in a dominant manner. It was discovered that an affected individual had one normal copy of chromosome 15 and one abnormal copy of chromosome 15 that was unusually long. How would you determine if the unusually long chromosome 15 was causing this disorder?arrow_forwardTwo phenotypically unaffected parents produce two children with familial Down syndrome. Regarding chromosome 14 and 21, what are the chromosomal composition of the parents?arrow_forwardMost cells in our bodies contain two sets of chromosomes (2x23=46) . Which types of cells each have only one set (23)?arrow_forward
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