What are the characteristics of Down's syndrome and how is complementary DNA and mRNA synthesized from a given DNA strand?

Down's syndrome is a genetic condition caused by an extra copy of chromosome 21.

a) Characteristics of an individual with Down's syndrome include:

• Intellectual disability (ranging from mild to moderate).
• Distinctive facial features such as a flattened facial profile, upward slanting eyes, and a small nose.
• Short stature and a short neck.
• Poor muscle tone (hypotonia).
• A single deep crease across the palm of the hand.

The given DNA strand sequence is G-C-C-T-A-G-A-T-C-A-C.

b) (i) The complimentary DNA strand.
In DNA, Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).
Given strand: G-C-C-T-A-G-A-T-C-A-C
Complementary DNA strand: C-G-G-A-T-C-T-A-G-T-G

The complimentary DNA strand is: $\boxed{\text{C-G-G-A-T-C-T-A-G-T-G}}$

b) (ii) The M-RNA strand copied from this DNA portion.
During transcription, DNA is used as a template to synthesize mRNA. In RNA, Uracil (U) replaces Thymine (T). So, A pairs with U, and G pairs with C.
Given DNA template strand: G-C-C-T-A-G-A-T-C-A-C
mRNA strand: C-G-G-A-U-C-U-A-G-U-G

The M-RNA strand is: $\boxed{\text{C-G-G-A-U-C-U-A-G-U-G}}$

Phenotypic characteristics selected for modern agricultural purposes aim to improve productivity, resilience, and quality.

18. Phenotypic characteristics selected for modern agricultural purposes include:

• High yield (increased production of crops or livestock products).
• Disease resistance (ability to withstand common plant or animal diseases).
• Pest resistance (resistance to insect pests).
• Drought resistance or tolerance to other adverse environmental conditions (e.g., salinity).
• Faster growth rate or shorter maturity period.
• Improved nutritional content (e.g., higher protein, vitamin, or mineral levels).