Bundle: Human Biology, Loose-leaf Version, 11th + MindTap Biology, 1 term (6 months) Printed Access Card
11th Edition
ISBN: 9781305616660
Author: Cecie Starr, Beverly McMillan
Publisher: Cengage Learning
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Chapter 20, Problem 2CT
Human sex chromosomes are XX for females and XY for males.
- a. With respect to an X-linked gene, how many different types of gametes can a male produce?
- b. If a female is homozygous for an X-linked allele, how many different types of gametes can she produce with respect to this allele?
- c. If a female is heterozygous for an X-linked allele, how many different types of gametes can she produce with respect to this allele?
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Butterflies 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.
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Drosophila, yellow body color is due to an X-linked gene that is recessive to the gene for gray body color.a. A homozygous gray female is crossed with a yellow male. The F1 are intercrossed to produce the F2. Give the genotypes and phenotypes, along with the expected proportions, of the F1 and F2 progeny.b. A yellow female is crossed with a gray male. The F1 are intercrossed to produce the F2. Give the genotypes and phenotypes, along with the expected proportions, of the F1 and F2 progeny.c. A yellow female is crossed with a gray male. The F1 females are backcrossed with gray males. Give the genotypes and phenotypes, along with the expected proportions, of the F2 progeny.d. If the F2 flies in part b mate randomly, what are the expected phenotypes and proportions of flies in the F3?
A young couple is planning to have children. Knowing that there have been a substantial number of stillbirths, miscarriages, and fertility problems on the husband’s side of the family, they see a genetic counselor. A chromosome analysis reveals that, whereas the woman has a normal karyotype, the man possesses only 45 chromosomes and is a carrier of a Robertsonian translocation between chromosomes 22 and 13. a. List all the different types of gametes that might be produced by the man. b. What types of zygotes will develop when each of gametes produced by the man fuses with a normal gamete produced by the woman? c. If trisomies and monosomies entailing chromosomes 13 and 22 are lethal, approximately what proportion of the surviving offspring are expected to be carriers of the translocation?
Chapter 20 Solutions
Bundle: Human Biology, Loose-leaf Version, 11th + MindTap Biology, 1 term (6 months) Printed Access Card
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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- For each of the following chromosome complements, what is the phenotypic sex of a person who has a. XY with the SRY gene deleted? b. XX with a copy of the SRY gene on an autosomal chromosome? c. XO with a copy of the SRY gene on an autosomal chromosome? d. XXY with the SRY gene deleted? e. XXYY with one copy of the SRY gene deleted?arrow_forwardAn individual heterozygous for a reciprocal translocation possesses the following chromosomes: A B • C D E F G A B • C D V W X R S • T U E F G R S • T U V W X a. Draw the pairing arrangement of these chromosomes in prophase I of meiosis. b. Diagram the alternate, adjacent-1, and adjacent-2 segregation patterns in anaphase I of meiosis. c. Give the products that result from alternate, adjacent-1, and adjacent-2 segregation.arrow_forwardChoose correct option and do explain. Considering an X-linked dominant trait, if an affected woman and an unaffected man decide to have children, which of the answer choices is possible for their children? a. All of their sons are expected to show the dominant trait. b. Their daughters are expected be heterozygous for the gene. c. Their daughters are not expected to show the dominant trait. d. Their sons are expected to be heterozygous for the gene. e. All their children, whether male or female, are expected to show the dominant trait.arrow_forward
- Barr bodies are formed to adjust X chromosome dosage in species other than humans, such as Drosophila (fruit flies) and C. elegans (nematodes). True or False ?arrow_forwardAn individual is heterozygous for a reciprocal translocation, with the following chromosomes: A • B C D E F A • B C V W X R S T • U D E F R S T • U V W X a. Draw a picture of these chromosomes pairing in prophase I of meiosis. b. Draw the products of alternate, adjacent-1, and adjacent-2 segregations. c. Explain why the fertility of this individual is likely to be less than the fertility of an individual without a translocation.arrow_forwardXX individuals can be sex-reversed males if one of their X chromosomes contains a translocated portion of the Y chromosome that includes the SRY gene. In light of what you now know about X-chromosome inactivation, it seems that this karyotype might have more complex consequences. In fact, although most such males are completely sex-reversed, X-chromosome inactivation can cause some of these XX males to have varying degrees of residual female characteristics. a. X-chromosome inactivation in normal XX embryos occurs earlier in development than SRY production in normal XY embryos. When present on a translocation X chromosome, SRY is subject to inactivation. Formulate a hypothesis to explain why many XX individuals with a translocation X chromosome that includes the SRY gene are not completely sex-reversed (male). b. Based on your answer to part (a), why do you think some individuals with this karyotype are completely sex-reversed?arrow_forward
- 3) A. How are the following proteins involved in cell division: condensing, cohesin, kinetochore complex, tubulin? B. Why does phenotype not always reveal genotype? C. How can Mendel's postulates of segregation and independent assortment be explained by meiosis? D. Explain the genotypic and phenotypic ratios predicted when performing a monohybrid and a dihybrid cross of heterozygotes? E. How can you use the product rule and sum rule to calculate the probability of a particular genotype resulting from crossing parents of specific genotypes?arrow_forwardHuman females have two X chromosomes (XX); males have one X and one Y chromosome (XY). a. With respect to X-linked alleles, how many different types of gametes can a male produce? b. If a female is homozygous for an X-linked allele, how many types of gametes can she produce with respect to that allele? c. If a female is heterozygous for an X-linked allele, how many types of gametes can she produce with respect to that allele?arrow_forwardAssume 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_forward
- Humans have two different sex chromosomes, X and Y. Figure 4 below shows the inheritance of sex in humans. Figure 4 Mother Father XX XX Y XY XY a) Copy the diagram into your answer booklet and draw a circle on the part of Figure 4 that shows an egg cell. b) What is the genotype of the male offspring? c) A man and a woman have two sons. The woman is pregnant with a third child. What is the chance that this child will also be a boy?arrow_forwardIn Drosophila, the X chromosomes may become attached to one another (XXn ) such that they always segregate together. Some flies thus contain a set of attached X chromosomes plus a Y chromosome. (a) What sex would such a fly be? Explain why this is so. (b) Given the answer to part (a), predict the sex of the off-spring that would occur in a cross between this fly and a normal one of the opposite sex. (c) If the offspring described in part (b) are allowed to interbreed, what will be the outcome?arrow_forwardColor blindness in humans is controlled by an X-linked completely recessive allele (Xc), while breast cancer is controlled by an autosomal completely dominant allele, B. A color blind male, who is a heterozygote carrier for breast cancer has three children/n with a normal eyed female (whose mother was color blind), who is homozygote recessive for the breast cancer allele. What is the probability that out of three children, 2 will be color blind males, and not show breast cancer, and one will be a color blind female, who shows breast cancer?arrow_forward
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