Describe the Lyon hypothesis What will be an ideal response?
ANSWER: Mary Lyon studied the inheritance of coat color in mice. Her discoveries, along with those of
other scientists, led her to propose her hypothesis about how dosage compensation works.
She concluded the following: Only one X chromosome is genetically active in the body cells
of female mammals. The second X chromosome is inactivated and tightly coiled to form the
Barr body. The inactivated chromosome can come from either parent. Inactivation takes
place early in development. After four to five rounds of mitosis following fertilization, each
cell of the embryo randomly inactivates one X chromosome. This inactivation is permanent
(except in germ cells), and all descendants of a particular cell will have the same X
chromosome inactivated. Because genes on only one X chromosome are expressed in
females, this equalizes the amounts of products from X-linked genes in males and females.
The Lyon hypothesis means that female mammals are actually mosaics, constructed of two
different cell types.
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What is the ploidy of an organism that is 7n, where n = 5?
A) 5 B) 7 C) 12 D) 35 E) 57
Two proteins, Rag-1 and Rag-2, catalyze VDJ recombination. What is the likely outcome of a deletion of the Rag genes?
A. mild susceptibility to infection due to T cell defects B. increased antibody diversity from B cells C. severe combined immunodeficiency (SCID) of both B and T cells D. increased resistance to infection due to enhanced B and T cell function Clarify Question What is the key concept addressed by the question? What type of thinking is required? Gather Content What do you already know about the VDJ segments? What other information is related to the question? Choose Answer Given what you now know, what information is most likely to produce the correct answer? Reflect on Process Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
A second-site mutation that compensates for the mutation in one gene by mutating a second gene and restoring the wild-type phenotype is also known as a ________ mutation
Fill in the blank(s) with correct word