The following is a diagram of nucleotides - HSC - SSCE Biology - Question 34 - 2010 - Paper 1

Component Z represents a nitrogenous base. In DNA, the bases are adenine (A), thymine (T), cytosine (C), and guanine (G). In RNA, the bases are adenine (A), uracil (U), cytosine (C), and guanine (G). Thus, the key difference is that thymine is present in DNA, while uracil replaces it in RNA.

Highly variable genes, often referred to as Variable Number Tandem Repeats (VNTRs) or Short Tandem Repeats (STRs), are used in DNA fingerprinting to identify individuals based on their unique genetic profiles. These regions of DNA vary greatly among individuals and can be analyzed through methods such as PCR and gel electrophoresis, making them invaluable in forensic science and paternity testing.

Germ line mutations occur in the reproductive cells and can be passed on to future generations. These mutations can lead to genetic diversity within a population, which may enhance adaptability to environmental changes. However, some mutations can also lead to hereditary diseases, which may diminish the fitness of the species over time.

Transposable genetic elements, often referred to as 'jumping genes', can move within and between genomes. Their movement can cause mutations, create genetic diversity, and influence gene expression by inserting into or disrupting coding regions or regulatory elements. This dynamic can drive evolution and adaptation, but it can also contribute to genetic disorders.