Question

Overall masculine development Gynaecomastia is expressed when fertilization occurs between
A. ${\text{Sperm }}\left( {{\text{22A + XY}}} \right) \times {\text{ Egg}}\left( {{\text{22A + XX}}} \right)$
B. ${\text{Sperm }}\left( {{\text{23A + Y}}} \right) \times {\text{ Egg}}\left( {{\text{22A + X}}} \right)$
C. ${\text{Sperm }}\left( {{\text{22A + XY}}} \right) \times {\text{ Egg}}\left( {{\text{22A + X}}} \right)$
D. ${\text{Sperm }}\left( {{\text{22A + X}}} \right) \times {\text{ Egg}}\left( {{\text{22A + 0}}} \right)$

Answer 1

As we know chromosomes are thread-like structures present in the nucleus that carries hereditary information in the form of genes which is passed from parents to offspring. When irregularities happen at the time of cell division, the chromosome's structure or number can be altered and these are known as chromosomal aberrations.

Complete Answer:
Gynecomastia can be explained as a condition in males where there is development of female characters like development of breast. It can be genetic or due to imbalance in hormone levels or can happen due to ageing also. Gynecomastia is a symptom found in Klinefelter syndrome.
Klinefelter syndrome is a chromosomal disorder in which there is addition of an extra X chromosome which occurs during the formation of reproductive cells like egg or sperm in any one of the affected person's parents. Because of an error called nondisjunction that happens during cell division, it prevents normal distribution of X chromosomes over the reproductive cells. Usually during the process of cell division, each egg cell gets a single X chromosome, and each sperm cell gets either an X chromosome or a Y chromosome but due to the occurrence of this error an egg cell or a sperm cell can also end up with an extra copy of the X chromosome resulting in an abnormal condition.
Klinefelter syndrome happens when an egg cell with an extra X chromosome (XX) is fertilized by a sperm cell with one Y chromosome or, if a sperm cell with both an X chromosome and a Y chromosome (XY) fertilizes an egg cell with a single X chromosome.
XXXY syndrome is a condition characterised by the presence of two extra X chromosomes in individuals. It is a condition of aneuploidy.
Down syndrome is a condition indicated by ${\text{45 + XY or 45 + XX}}$.
${\text{44 + X0}}$ indicates turner’s syndrome.

So, the correct answer is option C i.e. ${\text{Sperm }}\left( {{\text{22A + XY}}} \right) \times {\text{ Egg}}\left( {{\text{22A + X}}} \right)$.

Note: Any change in the base pair sequence of DNA is called a mutation. For example, changes like, deletion, insertion, duplication, substitution, etc. result in mutation and can change the genotype as well as the phenotype of an organism. There are two types of genetic mutations namely;
There are two types of genetic mutation:
-Point Mutation: There is a change only in the single base pair of DNAs like in the case of sickle cell anaemia.
-Frameshift Mutation: It happens due to the insertion or deletion of one or more pairs of bases in DNA. it changes the reading frame of triplet codons, that code for certain amino acids of the protein.