State one genetically different feature between sperms and eggs of humans. What is its consequence ?
State one genetically different feature between sperms and eggs of humans. What is its consequence ?
Official answer
In humans, all eggs produced by a female contain a single X chromosome as their sex chromosome. In contrast, sperms produced by a male are of two genetically different types: half of them carry an X chromosome, and the other half carry a Y chromosome.
Consequence: This genetic difference determines the sex of the child. If an egg is fertilized by an X-carrying sperm, the zygote develops into a girl (). If fertilized by a Y-carrying sperm, the zygote develops into a boy (). Thus, the father's sperm determines the sex of the offspring.
Marking scheme
- 1.Stating that eggs contain only X chromosome while sperms can contain either X or Y chromosome. (1 mark)
- 2.Explaining the consequence (determination of sex of the child based on the type of sperm fertilizing the egg). (1 mark)
Hint
Think about the sex chromosomes present in human males () and females () and how they segregate during gamete formation.
Quick oral answer
Sperms carry either an X or a Y chromosome, whereas eggs carry only an X chromosome. The consequence is that the sperm determines whether the child will be a boy or a girl.
Common mistakes
- 1.Believing that mothers determine the sex of the child because they carry the baby.
- 2.Confusing the chromosome composition of eggs and sperms.
Analysis and explanation
According to the NCERT text, women have a perfect pair of sex chromosomes, both called X. Therefore, all female gametes (eggs) carry an X chromosome. Men have a mismatched pair of sex chromosomes, one normal-sized X and one short Y. Consequently, male gametes (sperms) are of two types: 50% carry the X chromosome and 50% carry the Y chromosome. During fertilization, the fusion of an egg with an X-sperm results in a female child (), while fusion with a Y-sperm results in a male child (). This establishes that sex is genetically determined by the paternal contribution.
Interesting facts
In some reptiles, sex is determined by environmental temperature during egg incubation rather than genetics, while snails can even change their sex!
Question details
Q7 of 41 questions
- Board
- CBSE
- Class
- Class 10
- Subject
- Science
- Year
- 2012
- Section
- Section A
- Marks
- 2
- Type
- Short Answer
- Chapter
- Heredity
- Topic
- Sex Determination
- Bloom's level
- Understanding
- Syllabus topic
- Sex determination: Brief introduction
Spotted a mistake or something unclear?
Tell us and we will fix it.
Frequently asked questions
How many marks does this question carry in CBSE Class 10 Science 2012?
This question carries 2 marks in the CBSE Class 10 Science 2012 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Heredity" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Sex Determination" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2012 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2012 paper.