Genetic Material

• Ligase (A): Ligase is an enzyme that joins two open ends of DNA, typically during replication or repair, by forming phosphodiester bonds. Hence, (III).
• Helicase (B): Helicase unwinds the DNA double helix, separating the strands to facilitate replication or transcription. Hence, (IV).
• Gyrase (C): Gyrase is a type of topoisomerase that reduces topological strain in DNA caused by unwinding during replication. Hence, (I).
• Kinase (D): Kinase is an enzyme that adds phosphate groups to molecules, often modifying proteins or other substrates. Hence, (II).

1. A single subunit protein can form secondary structures like alpha helices and beta sheets, and it can also fold into a tertiary structure.
2. Quaternary structure involves interactions between multiple polypeptide chains, which a single subunit protein cannot achieve.

All the given statements correctly describe the characteristics and genetic basis of Sickle cell anemia, Red blood cells of people and Sickle cell trait.

• (A): In sickle cell anemia, the substitution of valine for glutamic acid occurs in the beta chain of hemoglobin at position 6, leading to abnormal hemoglobin (HbS) formation.
• (B): Individuals homozygous for the sickle cell allele (HbS/HbS) have red blood cells that collapse into a sickled shape under low oxygen conditions, causing blockages in blood vessels and reduced oxygen delivery.
• (C): Heterozygous individuals (HbA/HbS) are said to have the sickle cell trait. They generally do not exhibit severe symptoms but can experience mild symptoms under extreme conditions.

1. Turner's syndrome is a chromosomal abnormality caused by the absence of one X chromosome in females (45, XO).
2. Other conditions listed, such as emphysema and Lyme disease, are not related to chromosomal abnormalities.