Which of the following is considered a direct ancestor of modern humans (Homo sapiens)? MCQ with Answer and Explanation

Explanation:
DNA (deoxyribonucleic acid) is characterized by the presence of the pentose sugar deoxyribose in its nucleotide backbone. RNA (ribonucleic acid) contains the pentose sugar ribose. DNA is typically a double-stranded helical molecule, providing stability for long-term genetic storage. RNA is generally single-stranded, allowing it to fold into complex shapes and perform various functional roles like mRNA, tRNA, and rRNA. Thus, statements 1 and 2 are correct.

Explanation:
During DNA replication, the lagging strand is synthesized discontinuously in short segments called Okazaki fragments. After the RNA primers are removed and replaced with DNA by DNA polymerase I, the fragments remain separated by nicks in the sugar-phosphate backbone. DNA ligase is the enzyme that catalyzes the formation of phosphodiester bonds between these fragments, sealing the nicks and creating a continuous DNA strand.

Explanation:
The limbic system is a group of brain structures located on both sides of the thalamus, supporting emotion, behavior, motivation, long-term memory, and olfaction. The amygdala is an almond-shaped collection of nuclei located deep within the medial temporal lobes. It is a crucial component of the limbic system primarily associated with processing emotions, particularly fear, anxiety, and aggression. It plays a key role in the 'fight or flight' response and in attaching emotional significance to memories. The hippocampus is primarily for forming new declarative memories.