The functional part of the human genome is often referred to as the "coding DNA" or "exome." It consists of the regions that provide the instructions for making proteins. Proteins are the building blocks and functional molecules of cells and are essential for various biological processes.

The percentage of functional DNA in the human genome varies based on different estimates and definitions. Here's a general breakdown:

1. Protein-Coding DNA: This includes the DNA sequences that directly encode the instructions for creating proteins. Protein-coding DNA makes up approximately 1-2% of the total human genome.

2. Regulatory DNA: This includes DNA sequences involved in regulating when, where, and how protein-coding genes are expressed. Regulatory regions include promoters, enhancers, silencers, and other regulatory elements. Regulatory DNA is estimated to encompass around 10-20% of the human genome.

3. Non-Coding RNA (ncRNA): Non-coding RNA molecules, such as transfer RNA (tRNA), ribosomal RNA (rRNA), microRNA (miRNA), and long non-coding RNA (lncRNA), play important roles in various cellular processes. They make up approximately 1-5% of the human genome.

4. Functional Non-Coding DNA: There are DNA regions that don't directly code for proteins or ncRNAs but still have important functions. These include regions involved in chromosome structure, telomere maintenance, centromere function, DNA replication origins, and gene imprinting. The percentage of functional non-coding DNA is estimated to be around 5-10% of the genome.

5. Interspersed Repetitive Elements: These are repeated sequences (such as transposable elements or "jumping genes") that are interspersed throughout the genome. They make up a significant portion of the human genome (around 45-50%) but are largely non-functional in terms of protein-coding or regulatory functions.

In summary, while a small portion of our DNA (1-2%) directly encodes proteins, a larger portion (10-20%) is involved in gene regulation. Non-coding RNA and functional non-coding DNA contribute to cellular functions, and interspersed repetitive elements make up a substantial but non-functional part of the genome. Therefore, the functional DNA in the human genome is generally estimated to be around 20-30%, with the majority of the genome consisting of non-coding or repetitive sequences.