4. A fusion between a sperm, (n-1), and an egg, (n) will produce a zygote with......chromosomes.
A. trisomic.
B. monosomic.
C. autopolyploid.
D. autopolyploid.
E. Nullisomic
Answer (2)
The zygote formed by the fusion of a sperm with (n-1) chromosomes and an egg with (n) chromosomes will have a total of (2n - 1) chromosomes, which is classified as monosomic. This condition indicates that the zygote is missing one chromosome compared to the typical diploid number. The correct answer is B. monosomic.
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To understand the outcome of a fusion between a sperm cell with (n-1) chromosomes and an egg cell with n chromosomes, let's break it down:
Normal Chromosome Number (n):
In humans and other organisms with sexual reproduction, gametes (sperm and egg cells) typically have half the number of chromosomes found in somatic (body) cells. This ensures that when they fuse during fertilization, the resulting zygote has the correct diploid number of chromosomes.
Sperm with (n-1) Chromosomes:
If a sperm cell has (n-1) chromosomes, it means it is missing one chromosome that it should normally have. This can occur due to errors in cell division, such as nondisjunction during meiosis.
Egg with n Chromosomes:
An egg with the usual n chromosomes means it has the normal haploid number required.
Fusion of Sperm (n-1) and Egg (n):
When a sperm cell with (n-1) chromosomes fuses with a normal egg cell with n chromosomes, the resulting zygote will have a total of (n-1) + n = 2n - 1 chromosomes.
Answer - Monosomic:
A zygote with 2n - 1 chromosomes is described as monosomic. Monosomy refers to the condition where one chromosome from a pair is missing.
In multiple choice terms, the correct option is:
B. Monosomic
Monosomy is a type of aneuploidy, a condition where the chromosome number is not an exact multiple of the haploid number for the species. This can lead to developmental anomalies depending on which chromosome is affected.
