Human Biology: Concepts and Current Issues (8th Edition)
8th Edition
ISBN: 9780134042435
Author: Michael D. Johnson
Publisher: PEARSON
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Chapter 19, Problem 7AWK
Nondisjunction during meiosis can lead to the formation of gametes (sperm or eggs) with extra copies of one or more chromosomes. Normally, fertilizations involving extra copies of chromosomes simply do not result in a live birth because too many developmental events are altered in some way. The most common extra-chromosomal condition that does lead to live births is Down syndrome (trisomy 21). Why do you suppose that trisomy 21 is more common than other trisomies?
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On rare occasions, people are born with a condition known as uniparental disomy. It happens when an individual inherits both copies of achromosome from one parent and no copies from the other parent. Thisoccurs when two abnormal gametes happen to complement each otherto produce a diploid zygote. For example, an abnormal sperm thatlacks chromosome 15 could fertilize an egg that contains two copies ofchromosome 15. In this situation, the individual has maternal uniparental disomy 15 because both copies of chromosome 15 were inheritedfrom the mother. Alternatively, an abnormal sperm with two copies ofchromosome 15 could fertilize an egg with no copies. This is known aspaternal uniparental disomy 15. If a female is born with paternal uniparental disomy 15, would you expect her to be phenotypically normal,have Angelman syndrome (AS), or have Prader-Willi syndrome(PWS)? Explain. Would you expect her to produce normal offspring oroffspring affected with AS or PWS?
Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement but one (extra) chromosome 21. Given the fact that embryos with 48 chromosomes (four #21 chromosomes) are not likely to survive early development, what percentage of surviving offspring would be expected to have Down syndrome if both parents have Down syndrome?
all
2/3
1/2
1/3
none
Table 8.1 shows that Turner syndrome occurs when an individual inherits one X chromosome but lacks a second sex chromosome. Can Turner syndrome be due to nondisjunction during oogenesis, spermatogenesis, or both? If a phenotypically normal couple has a color-blind child (due to a recessive X-linked allele) with Turner syndrome, did nondisjunction occur duringoogenesis or spermatogenesis in this child’s parents? Explain your answer.
Chapter 19 Solutions
Human Biology: Concepts and Current Issues (8th Edition)
Ch. 19 - If you might be a carrier of a gene for an...Ch. 19 - Prob. 2QCCh. 19 - Prob. 1CRCh. 19 - Prob. 2CRCh. 19 -
3. Distinguish between genotype and phenotype.
Ch. 19 - Describe the contributions of Mendel to the field...Ch. 19 - Explain how alterations of chromosome number and...Ch. 19 - Prob. 6CRCh. 19 - Prob. 7CRCh. 19 - Describe what is meant by sex-linked inheritance.
Ch. 19 -
9. Explain why lethal diseases caused by dominant...Ch. 19 - Prob. 10CRCh. 19 - All of the following statements about homologous...Ch. 19 - Prob. 2TYCh. 19 -
3. Which of the following statements correctly...Ch. 19 - Prob. 4TYCh. 19 - Prob. 5TYCh. 19 - Prob. 6TYCh. 19 - Prob. 7TYCh. 19 - Which of the following results in the separation...Ch. 19 - Prob. 9TYCh. 19 - Prob. 10TYCh. 19 - What tool is used to determine the probabilities...Ch. 19 - Prob. 12TYCh. 19 - What is the basis for the tremendous genetic...Ch. 19 - Prob. 14TYCh. 19 -
15. Which of the following events or processes...Ch. 19 -
1. What fraction of the offspring of two...Ch. 19 -
2. Why is it that the range of resting blood...Ch. 19 - Prob. 3AWKCh. 19 - Geneticists often study patterns of gene transfer...Ch. 19 - Prob. 5AWKCh. 19 - Prob. 6AWKCh. 19 - Nondisjunction during meiosis can lead to the...
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- Assume that a meiotic-nondisjunction event causes trisomy 8 in a newborn. If two of the three copies of chromosome 8 are absolutely identical, at what point during meiosis did the nondisjunction event take place?arrow_forwardMen have XY (or YX) chromosomes and women have XX chromosomes. X-linked recessive genetic diseases (such as juvenile retinoschisis) occur when there is a defective X chromosome that occurs without a paired X chromosome that is not defective. Represent a defective X chromosome with lowercase x, so a child with the xY or Yx pair of chromosomes will have the disease and a child with XX or XY or YX or xX or Xx will not have the disease. Each parent contributes one of the chromosomes to the child. Complete parts a through d below. a. If a father has the defective x chromosome and the mother has good XX chromosomes, what is the probability that a son will inherit the disease? nothing (Type an integer or a decimal. Do not round.) b. If a father has the defective x chromosome and the mother has good XX chromosomes, what is the probability that a daughter will inherit the disease? nothing (Type an integer or a decimal. Do not round.) c. If a mother has one defective x…arrow_forwardMeiosis is also known as reduction cell division because it reduces the ploidy level from diploid (2n) to haploid (n). Why do we need to reduce our ploidy level in certain cells?arrow_forward
- In fruit flies, chromosomal crossing over does not occur in meiosis in males, whereas crossing over does occur in meiosis in females. In fruit flies that are heterozygous at many genes (i.e. many maternal and paternal versions of the genes differ), at what stage would cells no longer be heterozygous for any gene during the process of meiosis? a)After the second meiotic division in males, and after the first meiotic division in females. b)After the second meiotic division in both males and females. c)After the first meiotic division in both males and females. d)After the first meiotic division in males, and after the second meiotic division in females.arrow_forwardEXAMPLE 2: The parents in the family above produce another son, this time with two Y chromosomes and normal tooth enamel. In which parent did the nondisjunction occur? Explain and/or illustrate. Did nondisjunction occur at meiosis I or II? Explain and/or illustrate. What sex chromosomes are in the child’s somatic cells? This was not answeredarrow_forwardA cell has four pairs of chromosomes. Assuming that crossing over does not occur, what is the probability that a gamete will contain all of the paternal chromosomes? If n equals the number of chromosomes in a set, which of the following expressions can be used to calculate the probability that a gamete will receive all of the paternal chromosomes: (1/2)n, (1/2)n–1, or n1/2?arrow_forward
- During meiosis in male mammals, sex chromosomes segregate to produce two types of sperm: X‑bearing sperm and Y‑bearing sperm. True or false?arrow_forwardButterflies have an X-Y sex-determination system that is different from that of flies or humans. Female butterflies may be either XY or X0, while butterflies with two or more X chromosomes are males. This photograph shows a tiger swallowtail gynandromorph, which is half male (left side) and half female (right side). Given that the first division of the zygote divides the embryo into the future right and left halves of the butterfly, propose a hypothesis that explains how nondisjunction during the first mitosis might have produced this unusual-looking butterfly. Question is also in the picture.arrow_forwardIn humans, each cell normally contains a diploid (2n) chromosome number of 46. Say that a human body cell and sex cell will undergo mitosis and meiosis respectively, provide the number of chromosomes in each cell for every stage. Stage of Mitosis Number of Stages of Meiosis Number of Chromosomes in Chromosomes in One Cell One Cell Prophase 2n = Prophase 1 2n = Prometaphase 2n = Prometaphase 1 2n = Metaphase 2n = Metaphase 1 2n = Anaphase 2n = Anaphase 1 2n = Telophase and Cytokinesis Telophase 1 and Cytokinesis 2n = n = Prophase 2 Prometaphase 2 n = Metaphase 2 n = Anaphase 2 = u Telophase 2 and Cytokinesis n =arrow_forward
- Draw a diagram of Metaphase I and II of meiosis in the father, which illustrates the only possible way in which the father’s chromosomes could have aligned during Metaphase I, and in the subsequent Metaphase II in the same cell, in order to have resulted in the conception of the specific son who has all three of these genetic conditions (achondroplasia, color blindness and deafness).arrow_forwardA color-blind woman with Turner syndrome (XO) has a father who is color blind.Given that the gene for the color-blind condition is recessive and X-linked, provide a likely explanation for the origin of the color-blind and chromosome constitution in the color-blind woman. nondisjunction in the mother in meiosis I or II nondisjunction in the father at meiosis I no abnormalities had to occur to produce this daughter nondisjunction in the father in meiosis I or II nondisjunction in both the mother and father in meiosis I.arrow_forwardExtranuclear inheritance can involve genes that are present in: ribosomes mitochondria autosomes sex chromosomes In humans, which of the following would be phenotypically male? Question 5 options: XO individuals XX individuals XXY individuals XXX individuals Presence of an abnormal number of copies of an individual chromosome in a cell is a condition known as: triploidy heterogamy aneuploidy polyploidyarrow_forward
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