Textbook Question
Write a short essay that discusses sex chromosomes as they contrast with autosomes.
832
views
3. Extensions to Mendelian Inheritance
Sex Chromosome
1:46 minutesProblem 6
Textbook Question
How do mammals, including humans, solve the 'dosage problem' caused by the presence of an X and Y chromosome in one sex and two X chromosomes in the other sex?
Verified step by step guidance1
Understand that the 'dosage problem' refers to the imbalance in gene expression between males (XY) and females (XX) due to the difference in the number of X chromosomes.
Recognize that mammals solve this problem through a process called X-chromosome inactivation (XCI), which occurs in females.
Learn that XCI involves the random inactivation of one of the two X chromosomes in each cell of a female, effectively equalizing the dosage of X-linked genes between males and females.
Note that the inactivated X chromosome becomes a Barr body, which is a dense, compact structure that is transcriptionally inactive.
Realize that this process ensures that both males and females have a similar level of expression of genes located on the X chromosome, maintaining genetic balance.
Verified video answer for a similar problem:This video solution was recommended by our tutors as helpful for the problem above
Video duration:
1mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Dosage Compensation
Dosage compensation is a genetic mechanism that balances the expression of genes on sex chromosomes between males and females. In mammals, this is primarily achieved through X-inactivation, where one of the two X chromosomes in females is randomly inactivated, ensuring that gene dosage is similar to that of males, who have one X and one Y chromosome.
Recommended video:
Guided course
00:52
Purpose of X Inactivation
X-Inactivation
X-inactivation is a process that occurs in female mammals where one of the two X chromosomes is randomly silenced during early embryonic development. This results in a mosaic expression of X-linked genes, allowing females to maintain a similar level of gene expression from X-linked genes as males, thus addressing the potential imbalance in gene dosage.
Recommended video:
Guided course
09:30X-Inactivation
Sex Chromosomes
Sex chromosomes are a pair of chromosomes that determine the sex of an organism. In mammals, females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The presence of different sex chromosomes leads to variations in gene dosage, which is managed through mechanisms like dosage compensation to ensure proper development and function.
Recommended video:
Guided course
10:35Human Sex Chromosomes
Related Videos
Related Practice