Multiple Choice
In a sex-linked pedigree, if females are labeled as 'XX', how should males be labeled?
3
views
2. Mendel's Laws of Inheritance
Sex-Linked Genes
Struggling with Genetics?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Which statement most accurately explains why Duchenne muscular dystrophy (DMD) affects males more often than females?
A
Males produce more dystrophin protein, making them more susceptible to mutations.
B
Males have only one X chromosome, so a single mutated DMD gene will cause the disease.
C
DMD is caused by a dominant allele that is only present in males.
D
Females have two Y chromosomes, which protect them from DMD.
Verified step by step guidance1
Identify the inheritance pattern of Duchenne muscular dystrophy (DMD). DMD is an X-linked recessive disorder, meaning the gene responsible is located on the X chromosome.
Recall that males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). This difference is crucial for understanding why males are more affected.
Understand that because males have only one X chromosome, if that single X chromosome carries the mutated DMD gene, the male will express the disease since there is no second X chromosome to potentially carry a normal copy of the gene.
In contrast, females have two X chromosomes, so if one X chromosome has the mutated gene, the other X chromosome usually has a normal copy, which can compensate and prevent the disease from manifesting (making females typically carriers rather than affected).
Evaluate the incorrect options by considering the biology of sex chromosomes and gene expression: males do not produce more dystrophin protein inherently, DMD is not caused by a dominant allele, and females do not have two Y chromosomes.
Related Videos
Related Practice
Sex-Linked Genes practice set
Problem sets built by lead tutorsExpert video explanations