Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

2. Mendel's Laws of Inheritance

Sex-Linked Genes

Genetics

2. Mendel's Laws of Inheritance

Sex-Linked Genes

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Multiple Choice

X-linked recessive traits in humans (or in Drosophila) are observed most frequently in which group?

Males, because they have only one X chromosome

Equally in both males and females

Only in individuals with an extra X chromosome

Females, because they have two X chromosomes

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Verified step by step guidance

Understand the nature of X-linked recessive traits: these traits are associated with genes located on the X chromosome, and the recessive allele must be present on all X chromosomes for the trait to be expressed.

Recall that males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). This difference affects how X-linked recessive traits are expressed.

Since males have only one X chromosome, if they inherit the recessive allele on that X chromosome, they will express the trait because there is no second X chromosome to mask the effect.

Females, having two X chromosomes, must inherit two copies of the recessive allele (one on each X) to express the trait, which is statistically less likely.

Therefore, X-linked recessive traits are observed most frequently in males due to their single X chromosome, making them hemizygous for X-linked genes.