Concept explainers
Roberts syndrome is a rare inherited disorder characterized by facial defects as well as severe limb shortening, extra digits, and deformities of the knees and ankles. A cytogenetic analysis of patients with Roberts syndrome, using Giemsa staining or C-banding, reveals that there is premature separation of centromeres and other heterochromatic regions during mitotic metaphase instead of anaphase. A couple with an affected infant is contacted by a local organization dedicated to promoting research on rare genetic diseases, asking if they can photograph the infant as part of a campaign to obtain funding for these conditions. The couple learned that the privacy of such medical images is not well protected, and they often are subsequently displayed on public websites. The couple was torn between helping to raise awareness and promoting research on this condition and sheltering their child from having his images used inappropriately. Several interesting questions are raised.
If the parents decide to allow their infant to be photographed, what steps should the local organization take to ensure appropriate use and distribution of the photos?
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EBK CONCEPTS OF GENETICS
- Humans and many other complex organisms are diploid, possessing two sets of genes, one inherited from the mother and one from the father. However, a number of eukaryotic organisms spend most of their life cycles in a haploid state. Many of these eukaryotes, such as Neurospora and yeast, still undergo meiosis and sexual reproduction, but most of the cells that make up the organism are haploid. Considering that haploid organisms are fully capable of sexual reproduction and generating genetic variation, why are most complex eukaryotes diploid? In other words, what might be the evolutionary advantage of existing in a diploid state instead of a haploid state? And why might a few organisms, such as Neurospora and yeast, exist as haploids?arrow_forwardA somatic cell has the genotype DdEe. All chromosomes in this organism are metacentric. Show metaphase and the results of mitosis if the D and E locus are linked on the same chromosome in trans configuration. A sexually reproducing organism has the following phenotype DdEeAaTt: The D and E loci are on the same arm of a metacentric chromosome in cis configuration. The A locus is on the long arm of an acrocentric chromosome and the T locus is on a telocentric chromosome. 2.1. What is the haploid number of this organism? 2.2. Using diagrams show a ceii at metaphase of mitosis and show the results of mitosis.arrow_forwardFor below problem, consider a diploid cell that contains three pairs of chromosomes designated AA, BB, and CC. Each pair contains a maternal and a paternal member (e.g., Am and Ap). Using these designations, demonstrate your understanding of mitosis and meiosis by drawing chromatid combinations as requested. Be sure to indicate when chromatids are paired as a result of replication and/or synapsis. You may wish to use a large piece of brown manila wrapping paper or a cut-up paper grocery bag for this project and to work in partnership with another student. We recommend cooperative learning as an efficacious way to develop the skills you will need for solving the problems presented throughout this text. Question: Assume that each gamete resulting from Problem 29 fuses, in fertilization, with a normal haploid gamete. What combinations will result? What percentage of zygotes will be diploid, containing one paternal and one maternal member of each chromosome pair?arrow_forward
- consider a diploid cell that contains three pairs of chromosomes designated AA, BB, and CC. Each pair contains a maternal and a paternal member (e.g., Am and Ap, etc.). Using these designations, demonstrate your understanding of mitosis and meiosis by drawing chromatid combinations as requested. Be sure to indicate when chromatids are paired as a result of replication and/or synapsis. You may wish to use a large piece of brown manila wrapping paper or a large cut-up paper bag and work with another student as you deal with these problems. Such cooperative learning may be a useful approach as you solve problems throughout the text. Draw all possible combinations of chromatids during anaphase II in meiosis.arrow_forwardColchicine is a chemical mutagen that inhibits the spindle formation and prevents anaphase, which retains the cell’s single restitution nucleus (doubled chromosome number). Suppose that an onion (2n=16) is subjected to three consecutive rounds of colchicine treatment, what will be the resulting chromosome number of the treated onion?arrow_forwardVariations in Chromosome NumberAneuploidy Describe the process of nondisjunction and explain when it takes place during cell division.arrow_forward
- 1). A diploid somatic cell from a dog (Canis lupus familiaris) has a total of 78 chromosomes (2n = 78). As in humans, sex chromosomes determine sex: XX in females and XY in males. a) What is the total number of DNA molecules in G2 of the cell cycle? b) What is the total number of sister chromatids during prometaphase? c) What is the total number of telomeres in a somatic dog cell in G1? d) What is the total number of autosomes?arrow_forwardIf a gamete of an unknown animal species has 18 chromosomes, how many chromatids are at anaphase I? If a gamete of an unknown animal species has 18 chromosomes, how many chromatids are at telophase II? If a gamete of an unknown animal species has 18 chromosomes, how many centromeres after prophase II? If a gamete of an unknown animal species has 18 chromosomes, how many chromosomes are in after anaphase II? If a gamete of an unknown animal species has 18 chromosomes, how many chromosomes are in at metaphase I? PLEASE ANSWER ALL OF THEM THEY ARE ALL CONNECTED, THANK YOU!arrow_forwardillustrate and briefly describe the alignment, pairing, and disjunction ofsister chromatids during mitosis. Include the molecular complexes cohesin and shugoshin and the enzyme separase.arrow_forward
- Human somatic cells have 46 chromosomes. Are the cells different in any way from the parent cell and what is chromosome count of each of those cells once they have finished mitosis?arrow_forwardPrader-Willi syndrome and Angelman syndrome are both caused by deletion of a set of genes onchromosome 15. The symptoms of Prader-Willi syndrome are short stature, small hands andfeet, hypotonia (floppiness), hypogonadism, mild mental retardation, and an uncontrollabledesire to eat (polyphagia). Angelman syndrome is characterized by an intellectual anddevelopmental delay, sleep disturbances, seizures, hand-flapping and other jerky movements,frequent laughter or smiling, and usually a happy demeanor.Please explain how the deletion of the same set of genes can result in such different diseases. Inyour answer, be sure to discuss the role of genetic imprinting and epigenetics.arrow_forwardConsider the following two meiocytes in metaphase I, with crossover positions as indicated for cell A. Solid black lines indicate spindle microtubules. Assume blue chromosomes represents paternal chromosomes and green maternal chromosomes. F G N R A B D e g a B d E Cell A Cell B i) How many chromosomes and chromatids were present in cell A during the G1 phase? Please clearly specify chromosomes and chromatids in your answer. ii) For cell A, list all the gametes that will be produced from this cell. Give the alleles of each gamete contained within a set of brackets. You may ignore independent assortment. iii) For cell B, list all the gametes that will be produced from this cell given independent assortment. Give the alleles of each gamete contained within a set of brackets. You may assume that no crossing over would take place.arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning