Over a period of two years, a man in his early 20s received a series of intermittent chemotherapy and radiotherapy treatments for Hodgkin disease. During this therapy, he and his wife were unable to initiate a pregnancy. The man had a series of his semen samples examined at a fertility clinic. The findings revealed that shortly after each treatment very few mature sperm were present, and abnormal chromosome numbers were often observed in developing spermatocytes. However, such chromosome abnormalities disappeared about 40 days after treatment, and normal sperm reappeared about 74 days post-treatment. Do you think that exposure to chemotherapy and radiotherapy would cause more problems to spermatocytes than to mature sperm?
Want to see the full answer?
Check out a sample textbook solutionChapter 2 Solutions
EBK CONCEPTS OF GENETICS
- In the past, the IOC has employed two genetic sex- determination tests. The Barr body test screens for the presence of two X chromosomes. In XX somatic cells, one copy of the X chromosome condenses into a largely inactive structure called a Barr body, which can be seen using a light microscope. In more recent years, a polymerase chain reaction-based screen has been used to amplify the DNA sequence of the SRY gene, which is found only on the Y chromosome. Based on their karyotypes, what would be the outcome of these two tests for each of the four individuals? Drag the labels to indicate the presence or absence of a Barr body and the SRY gene sequence.arrow_forwardStructurally, meiotic cohesins have different components than mitotic cohesins. This leads to what function differences?arrow_forwardChorionic villus sampling is a procedure to determine if there are any abnormalities in chromosome number in the fetus. Why can the chorionic villi be used to determine abnormalities in the fetus?arrow_forward
- a. What type of cell division mitosis, meiosis I or meiosis II is shown in this figure? b. What is the diploid number of this organism? c. Provide labels for (i) and (ii)arrow_forwardOn 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?arrow_forwardA normal somatic cell in horses has 64 chromosomes. Give the number of chromosomes and number of DNA molecules that will be present in the following horse cells: spermatogonia, first polar body, primary oocyte and, secondary spermatocyte.arrow_forward
- Including the sex chromosomes, the chromosome number of a normal human cell is and the chromosome number of this Hela cell is - (Hint: Chromosome number is different from total chromosome count.) It appears that this Hela cell has extra copies of chromosome 16. Henrietta Lacks was female, so, naturally, all the cells from her derived cancerous cell line have chromosomes. This HeLa cell, interestingly, has copies of its sex chromosomes. What sex is the normal human karyotype displayed here? O Male O Femalearrow_forwardWhy is X chromosome inactivation important in female cells? (300 word limit)arrow_forwardThe picture below represents a G1 cell from a newly discovered species that uses the X/Y sex determination system. Alleles for the different autosomal genes of interest are indicated on the chromosomes, and genes R and T are 16 cM apart. Red lines show maternal chromosomes, and blue lines show paternal chromosomes. Answer the following questions about this individual.d) Provide the genotype of the fertilizing male gamete that produced this individual. e) This individual can produce a pool of different gametes. List any TWO potential gametes that will occur at different frequencies. Give the alleles of each gamete contained within a set of brackets, and indicate the expected frequency (up to two decimals) at which that gamete would occur.arrow_forward
- Mutations in genes that affect meiosis have been identified in many different model organisms. Most of these mutations result in aneuploidy of more than a single chromosome and are nearly sterile. Explain why this is the case.arrow_forwardWhy is aneuploidy of the sex chromosomes less debilitating than aneuploidy of even the smallest autosomes? (Note: multiple responses are correct, please choose the best answer(s)) Select one or more: Only one X chromosome is required at any given time. Additional X chromosomes (as in females) are inactivated in most cells except for gametes Dosage compensation requires that all excess chromosomes (i.e. 2 or more) are activated at all times during the cell cycle The Y chromosome carries a number of critical genes involved in spermatogenesis and sex development. Therefore, having two copies of the Y chromosome results in the overproduction of sperm and increased fertility The Y chromosome carries a number of critical genes required for spermatogenesis and sex development, but very few other genes. Therefore, having two copies of the Y chromosome has minimal impact on the balance of gene expressionarrow_forwardA human female with Turner syndrome (45,X) also expresses the X-linked trait hemophilia, as did her father. Which of her parents underwent nondisjunction during meiosis, giving rise to the gamete responsible for the syndrome?arrow_forward
- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning