12. Explain the following terms used in genetics: (i) Heredity (ii) Gene (iii) Chromosome - Leaving Cert Biology - Question 12 - 2021

A gene is a segment of DNA that encodes information for the synthesis of a protein or functionally important RNA molecule. It acts as a unit of heredity and plays a crucial role in determining specific traits.

A chromosome is a long, continuous thread of DNA that contains numerous genes along with regulatory elements. It is, essentially, a condensed structure that compacts the DNA for cell division.

A molecule of DNA consists of two strands that are arranged in a double helix formation.

'Junk DNA' refers to regions of DNA that do not code for proteins. These segments may have no known function or purpose, although some are believed to play roles in gene regulation and maintaining chromosome structure.

A complementary base pair in DNA consists of Adenine (A) pairing with Thymine (T), and Guanine (G) pairing with Cytosine (C).

Before replication begins, the two strands of DNA separate at certain points, allowing each strand to serve as a template for the synthesis of a new complementary strand.

The complementary structure to DNA involved in protein synthesis is RNA, specifically messenger RNA (mRNA).

RNA differs from DNA in that it is typically single-stranded, while DNA is double-stranded. Additionally, RNA contains ribose sugar instead of deoxyribose and uses uracil (U) in place of thymine (T).

Amino acids are the smaller molecules that are linked together through peptide bonds to form a protein molecule.

A codon is a sequence of three nucleotides in DNA or RNA that encodes for a specific amino acid in the process of protein synthesis.

The further step required is for the amino acid chains to undergo folding and post-translational modifications to achieve their functional three-dimensional structure.

Cancer is characterized by uncontrolled cell division, which leads to the formation of tumors and potentially spreads throughout the body.

Two causes of cancer include 1) cigarette smoking and 2) exposure to radiation or harmful chemicals such as asbestos.

The two types of cell division are Mitosis and Meiosis. One difference is that Mitosis results in two genetically identical cells, while Meiosis results in four genetically different cells.

Mitosis and Interphase can be illustrated together showing Interphase as the preparatory phase where cells grow and duplicate their DNA, followed by Mitosis where the cell divides.