Multiple Choice
Linked genes are __________.
29. Heredity
Patterns of Inheritance
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If a male inherits a sex-linked gene for color blindness, __________.
A
it will only be expressed 25% of the time
B
it will never be expressed
C
it will always be expressed
D
it will be expressed only if two copies are present
Verified step by step guidance1
Understand that sex-linked genes are located on the sex chromosomes, which are X and Y in humans.
Recognize that color blindness is a recessive trait linked to the X chromosome.
Recall that males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).
Since males have only one X chromosome, any recessive gene on it, such as the one for color blindness, will be expressed because there is no corresponding gene on the Y chromosome to mask it.
Conclude that if a male inherits a sex-linked gene for color blindness, it will always be expressed because there is no second X chromosome to potentially carry a dominant normal vision allele.
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