Multiple Choice
In eukaryotic cells, which process is primarily prevented by heterochromatin formation during X-inactivation?
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3. Extensions to Mendelian Inheritance
X-Inactivation
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
How does a calico cat obtain its unique coat pattern?
A
Calico cats inherit their coat pattern from their fathers only.
B
A mutation in mitochondrial DNA causes the patchy coloration.
C
Random X-inactivation in each cell leads to different alleles being expressed for fur color.
D
The coat pattern is determined solely by environmental factors affecting pigment distribution.
Verified step by step guidance1
Understand that calico coat patterns are a classic example of X-linked genetic expression, where the gene for fur color is located on the X chromosome.
Recall that female mammals have two X chromosomes (XX), while males have one X and one Y chromosome (XY). This difference is crucial for understanding calico patterns.
Learn about the process called X-inactivation (also known as lyonization), where in each cell of a female, one of the two X chromosomes is randomly inactivated during early embryonic development.
Recognize that because of random X-inactivation, some cells express the allele from one X chromosome (e.g., for orange fur), while other cells express the allele from the other X chromosome (e.g., for black fur), leading to the patchy, mosaic coat pattern seen in calico cats.
Note that this pattern is not inherited solely from the father, nor caused by mitochondrial DNA mutations or environmental factors, but is a direct result of random X-inactivation in female cats.
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