Question
A child exhibits characteristics associated with Down syndrome. A karyotype of the childs cells shows the results pictured.
image
What is the most likely reason for this occurrence?
A.
Nondisjunction occurs in all of the cells of the child resulting in the disorder.
B.
The abnormality is the result of crossing over during meiosis in the gametes of the parents.
C.
The child has Down Syndrome due to nondisjunction occurring in one of the gametes of the parents.
D.
Crossing over occurred during the process of mitosis of the all of the cells of child suffering from Down's Syndrome.
image
What is the most likely reason for this occurrence?
A.
Nondisjunction occurs in all of the cells of the child resulting in the disorder.
B.
The abnormality is the result of crossing over during meiosis in the gametes of the parents.
C.
The child has Down Syndrome due to nondisjunction occurring in one of the gametes of the parents.
D.
Crossing over occurred during the process of mitosis of the all of the cells of child suffering from Down's Syndrome.
Answers
Answered by
GPT-4o mini
The most likely reason for a child exhibiting characteristics associated with Down syndrome and showing the karyotype that indicates the presence of an extra chromosome 21 is:
**C. The child has Down Syndrome due to nondisjunction occurring in one of the gametes of the parents.**
Nondisjunction is the failure of chromosomes to separate properly during cell division, leading to gametes with an abnormal number of chromosomes. This can result in a zygote with an extra chromosome (trisomy), which is what causes Down syndrome (trisomy 21). Choices A and D refer to nondisjunction or crossing over occurring in ways that are not relevant to the child’s condition. Choice B wrongly attributes the abnormality to crossing over during meiosis, which does not lead to the formation of an extra chromosome.
**C. The child has Down Syndrome due to nondisjunction occurring in one of the gametes of the parents.**
Nondisjunction is the failure of chromosomes to separate properly during cell division, leading to gametes with an abnormal number of chromosomes. This can result in a zygote with an extra chromosome (trisomy), which is what causes Down syndrome (trisomy 21). Choices A and D refer to nondisjunction or crossing over occurring in ways that are not relevant to the child’s condition. Choice B wrongly attributes the abnormality to crossing over during meiosis, which does not lead to the formation of an extra chromosome.