XX 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?

XX 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?

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Description: XX individuals can be sex-reversed males if one of their X chromosomes contains a translocatedportion of the Y chromosome that includes the SRY gene. In light of what you now know aboutX-chromosome inactivation, it seems that this karyotype might ha

BIOLOGY:CONCEPTS+APPL.(LOOSELEAF)

10th Edition

ISBN:9781305967359

Author:STARR

Publisher:STARR

Chapter14: Human Inheritance

Section: Chapter Questions

Problem 2GP: Human females have two X chromosomes XX; males have one X and one Y chromosome XY. a. With respect...

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Human 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. A female homozygous for an X-linked allele can produce how many types of gametes with respect to that allele? c. A female heterozygous for an X-linked allele can produce how many types of gametes with respect to that allele?
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 ?
Explain why a person with Klinefelter Syndrome (XXY) still exhibits abnormal phenotypes despite the fact that one of the extra X Chromosome is inactivated practically leaving an XY active sex chromosomes similar to a normal male?
In dosage compensation, do males sometimes overcompensate or is it always Barr body X-chromosome inactivation for females?
. Researchers discovered recently that the sole functionof the SRY protein is to activate an autosomal genecalled Sox9 in the presumptive gonad (before it has“decided” to become a testis or an ovary).a. What would be the sex of an XY individual homozygous for nonfunctional mutant alleles of Sox9?Explain.
Which of the following statements is false? Dosage compensation is accomplished in humans by stimulation of gene expression from the single X chromosome. Dosage compensation is accomplished in humans by inactivating a female X chomosome. An individual with Turner Syndrome has no Barr bodies. An individual with Klinefelter syndrome generally has one Barr body. A typical XX human female has one Barr body.
Researchers discovered recently that the sole functionof the SRY protein is to activate an autosomal genecalled Sox9 in the presumptive gonad (before it has“decided” to become a testis or an ovary).a. What would be the sex of an XY individual homozygous for nonfunctional mutant alleles of Sox9?Explain.b. Given your answer to part (a), why is SRY, ratherthan Sox9, considered the male determining factor?(Hint: What do you think would happen if you didan experiment like the one in the Fast Forward BoxTransgenic Mice Prove That SRY Is the MalenessFactor, except that you used a Sox9 transgeneinstead of SRY?)
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. Question is also in the picture.
Chromosomal nondisjunction of the X chromosome in female gametes of humans means that live offspring can include ________. A) females with XX or XXX, and males with XY or XXY B) females with XX, and males with XY C) females with XX, and males with XY or XO D) females with XX or XXX, and males with XY or XO E) females with XX or XO, and males with XY or OY
Describe when X-chromosome inactivation occurs and how thisleads to phenotypic results at the organism level. In your answer,you should explain why XCI causes results such as variegated coatpatterns in mammals. Why do two different calico cats have theirpatches of orange and black fur in different places? Explainwhether or not a variegated coat pattern due to XCI could occur inmarsupials.
The gene for the production of eye colour in this species of fruit fly can be expressed aseither normal red-eyes or as brown-eyes. The allele for the normal red eyes is dominant tothat of brown, and is transmitted in normal Mendelian fashion.A gene involved with body colour in this species of fruit fly is located on the non-homologousportion of the X chromosome, and has two alleles, grey and yellow, where the grey allele isdominant to yellow.The two genes are NOT linked.a) Produce a key to clearly show the nature of the alleles associated with the eye colour inthis species of Drosophila, and in each case justify your choice of letters and / or style ofpresentation to best depict the genetics involved.
Why is it that so many of the sex-linked traits we talk about in humans are carried on X chromosomes - but are expressed mostly in males?