How many chromosomes in a normal human karyotype
The Correct Answer and Explanation is :
A normal human karyotype consists of 46 chromosomes, arranged in 23 pairs. This includes 22 pairs of autosomes (non-sex chromosomes) and 1 pair of sex chromosomes. The sex chromosomes determine a person’s biological sex: females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
Explanation of Chromosome Structure:
Chromosomes are thread-like structures composed of DNA and proteins, which carry the genetic information necessary for growth, development, and reproduction. Each chromosome contains many genes, and humans have around 20,000-25,000 genes spread across their chromosomes. In humans, the 23 pairs of chromosomes are numbered from 1 to 22 based on size, with chromosome 1 being the largest.
- Autosomes (Chromosomes 1-22): These chromosomes are not involved in determining the sex of an individual. They carry genes that are essential for various bodily functions, including development, immune function, and metabolism. Each person inherits one chromosome of each pair from their mother and one from their father.
- Sex Chromosomes (Pair 23): These chromosomes determine the biological sex of an individual. Females typically have two X chromosomes (XX), and males have one X and one Y chromosome (XY). The X chromosome is much larger than the Y chromosome and carries many more genes. The presence of a Y chromosome triggers the development of male characteristics, while the absence of a Y chromosome results in the development of female characteristics.
Karyotype and Genetic Disorders:
A karyotype is a laboratory procedure that examines the number and structure of chromosomes. A normal karyotype shows 46 chromosomes in total (23 pairs). However, abnormalities in chromosome number or structure can lead to genetic disorders. For example:
- Down syndrome (Trisomy 21) occurs when there is an extra copy of chromosome 21, resulting in 47 chromosomes.
- Turner syndrome occurs when there is only one X chromosome in females (45 chromosomes in total).
In conclusion, a normal human karyotype consists of 46 chromosomes, which are essential for proper genetic function and inheritance.