Human Genome and Nucleic Acids Quiz

Study Notes

Approximately 30,000 genes are present in the human genome.
About 20% of the genome includes introns, untranslated regions, and pseudogenes.
Extragenic regions make up around 75% of the human genome.
Repeated sequences constitute 55% of the genome.
Repetitive sequences primarily consist of transposons, which can insert multiple copies in scattered locations.

Nucleic acids are carriers of genetic information, composed of two types: DNA and RNA.
DNA (Deoxyribonucleic Acid) contains deoxyribose, while RNA (Ribonucleic Acid) contains ribose.
Both nucleic acids feature a sugar-phosphate backbone and nitrogenous bases.

Nitrogenous bases include:
- Pyrimidines: Thymine (T) and Cytosine (C).
- Purines: Adenine (A) and Guanine (G).
RNA contains uracil (U) instead of thymine (T).
Base pairing is complementary: A:T and G:C, with G:C bonds being more stable due to three hydrogen bonds compared to two in A:T.

DNA forms a double helix with two anti-parallel strands (5’ to 3’ and 3’ to 5’).
DNA replication occurs during the S phase of the cell cycle, facilitated by DNA polymerase.
Leading strand synthesized continuously (5’ to 3’ toward replication fork); lagging strand synthesized discontinuously in fragments (5’ to 3’ away from replication fork).
RNA primers are necessary for initiating DNA synthesis.

Genes include exons (protein-coding regions), introns (noncoding regions involved in regulation), and flanking sequences (5’ and 3’ ends controlling gene expression).
Around 30,000 protein-coding genes exist, along with several thousand RNA genes, including ribosomal RNA (727 genes) and transfer RNA (131 genes).
RNA molecules are crucial for gene expression regulation, inclusive of microRNAs and small RNAs derived from introns.

Missense mutations substitute one amino acid, while nonsense mutations create stop codons, truncating proteins.
Single-Nucleotide Polymorphisms (SNPs) can affect gene expression; those in regulatory regions or introns may alter regulatory binding or splicing.
SNPs in noncoding regions can influence post-transcriptional regulation.

Secondary structures of proteins, such as α-helices and β-sheets, arise primarily from hydrogen bonding.
The tertiary structure refers to the three-dimensional arrangement, which may include domains.
Glycosylation (adding carbohydrates) is a common post-translational modification (PTM) in eukaryotic proteins, especially extracellular ones.
Other PTMs like carboxylation and hydroxylation influence protein function through calcium ion binding.

Pharmacogenomics integrates DNA sequence data to predict drug responses based on phenotypes.
Phenotype determines observable traits, influenced by genotype and environmental factors.
Phenotype frequency is the ratio of affected individuals to the total in the population, for example, a 3% prevalence of atorvastatin-induced myopathy.
Simple phenotypes may be either dominant (expressed with one allele) or recessive (expressed only in homozygous form).
Complex traits arise from multiple genetic and environmental factors, exemplified by conditions like diabetes.