1. 23 pairs of chromosomes are present.
2. Chromosomes are paired according to size, banding pattern, and centromere position. The homologous chromosomes are arranged in descending order by size, with the sex chromosomes placed at the end. This allows for easy identification of any abnormalities or variations.
3. Since the sex chromosomes are different (one X and one Y), the individual is male.
4. The diploid number is 46. The haploid number is 23.
5. 23 pairs of chromosomes are present.
6. Chromosome 21 has the abnormality.
7. Down syndrome is caused by an extra copy of chromosome 21 (trisomy 21). This results from nondisjunction during meiosis, where chromosome 21 fails to separate properly, leading to a gamete with two copies instead of one. When this gamete combines with a normal gamete, the resulting zygote has three copies of chromosome 21. This extra genetic material disrupts normal development, causing the characteristic physical features and intellectual disabilities associated with Down syndrome.
Parent Tip: Review the logic above to help your child master the concept of karyotypes worksheet.
