All female mammals have one active X chromosome per cell instead of two. What causes this?
A) activation of the XIST gene on the X chromosome that will become the Barr body
B) activation of the BARR gene on one X chromosome, which then becomes inactive
C) inactivation of the XIST gene on the X chromosome derived from the male parent
D) attachment of methyl (CH3 ) groups to the X chromosome that will remain active
A
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The phenotypic changes shown in the figure above represent
A. punctuated equilibrium.
B. horizontal gene transfer.
C. gradualism.
D. speciation based on sexual selection.
The part of the plant that is a waxy coating that minimizes water loss from leaves is the:
a. Stomata b. Root c. Xylem d. Phloem e. Cuticle
The lowermost and outermost whorl on a floral shoot consists of petals
____________________ Indicate whether the statement is true or false.
Removing genes from molecules of DNA requires the use of special
A. enzymes from peroxisomes. B. digestive enzymes. C. microscopic scalpels. D. restriction enzymes.