Question

A group of transposable elements described as retroelements encompass

• A. P elements in Drosophila; LINES but not SINES in humans
• B. Copia elements in Drosophila; SINES but not LINES in humans
• C. Copia element in Drosophila; LINES as well as SINES in humans
• D. P elements in Drosophila; LINES as well as SINES in humans

Hint:

Remember the key distinction: Retroelements use an RNA intermediate and reverse transcriptase ('retro' = backwards from RNA to DNA). DNA transposons move directly as DNA. Key examples are Copia/LINES/SINES for retroelements and P elements for DNA transposons.

Answer 1

The Correct Option is C

Step 1: Introduction to Transposable Elements:
Transposable elements (TEs) are DNA sequences that move within a genome. They are divided into two main classes. The task is to find examples of retroelements.
Class I TEs (Retroelements or Retrotransposons): These elements use a "copy-and-paste" method. They are transcribed into RNA, then reverse-transcribed back into DNA by reverse transcriptase. This new DNA copy inserts into a new genome location. Class II TEs (DNA Transposons): These use a "cut-and-paste" mechanism. The DNA element is removed and inserted elsewhere, a process done by transposase. Step 2: Element Classification:
Let's classify the options:
P elements in Drosophila are Class II DNA transposons, using "cut-and-paste". Copia elements in Drosophila are LTR-retrotransposons, a type of Class I retroelement. LINES (Long Interspersed Nuclear Elements) in humans are non-LTR retrotransposons, a major Class I retroelement. SINES (Short Interspersed Nuclear Elements) in humans are also non-LTR retrotransposons (Class I). They are "non-autonomous" and rely on other elements like LINES for movement. Option analysis:
(A) is wrong because P elements are DNA transposons, not retroelements. (B) is wrong because both SINES and LINES are retroelements in humans. (C) is correct. It correctly identifies Copia as a retroelement in Drosophila, and both LINES and SINES as retroelements in humans. (D) is wrong because P elements are DNA transposons. Step 3: Conclusion:
The retroelements are Copia in Drosophila, and LINES and SINES in humans.