Question

question #1
which statement best explains why male mice do not use xist rna for xci?
a males require a type of yist rna for y chromosome inactivation
b only the x chromosome in females contains genes
c the x and y sex chromosomes contain different genes
d xci only occurs when the x chromosome is damaged
question #2
which of the following aspects of a dna molecule is responsible for determining the traits of an organism?
a number of phosphates
b amount of thymine
c sequence of nucleotides
d type of bond between bases

Explanation:

For Question #1:

X-chromosome inactivation (XCI) is a process that only occurs in female mammals (with two X chromosomes) to balance gene dosage, mediated by Xist RNA. Male mice have one X and one Y chromosome, so XCI is not needed. Option C is incorrect; the key is gene dosage, not different genes on X/Y. Option A is incorrect as there is no "Yist RNA" for Y inactivation. Option D is incorrect because XCI is not triggered by damaged X chromosomes. The correct reasoning is that XCI is a female-specific dosage compensation mechanism, so male mice do not use Xist RNA for XCI (the best fitting option among the choices, as the core reason is XCI is only for females with two Xs, and option B is the only one that aligns with the context that female X chromosomes are the ones relevant to XCI, as males don't have two Xs to inactivate).

For Question #2:

The traits of an organism are determined by the genetic code stored in DNA. The sequence of nucleotides (A, T, C, G) in DNA encodes the information for proteins and functional RNAs, which directly determine traits. The number of phosphates, amount of thymine, and type of bond between bases do not carry the unique genetic information that defines an organism's traits.

Answer:

Question #1: B. Only the X chromosome in females contains genes
Question #2: C. sequence of nucleotides