Concise Genetics and Cell Function Notes

Genetic Control of Cell Function

Genetic information stored in DNA directs cell function, appearance, response to the environment, and inheritance.
Completion of the Human Genome Project in 2003 and subsequent innovations have expanded the understanding of genetics in disease.
DNA's stable structure allows it to survive cell division, gamete formation, fertilization, and mitotic divisions.
RNA is involved in the synthesis of cellular proteins using information transcribed from DNA.
Proteins, encoded by genes, constitute cellular structures and perform biological functions and are targets for many drugs.

DNA is a double-stranded, helical structure composed of nucleotides.
Nucleotides consist of phosphoric acid, deoxyribose (a five-carbon sugar), and a nitrogenous base (adenine, guanine, cytosine, or thymine).
Base pairing rules: Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).
DNA replicates semiconservatively, with each new DNA molecule consisting of one old strand and one new strand.
DNA is packaged into chromosomes with the help of proteins like histones, forming a tightly coiled structure called chromatin.
Chromatin remodeling, such as acetylation (gene activation) and methylation (gene inactivation), affects gene accessibility.

Mutations are errors in DNA replication, which can occur spontaneously or due to environmental factors.
DNA repair mechanisms, involving enzymes like endonucleases and DNA polymerase, correct most defects.
Variations in gene sequence (0.01%) account for individual differences; these variations are called polymorphisms.

RNA assembles amino acids into proteins through translation.
RNA differs from DNA by being single-stranded, containing ribose instead of deoxyribose, and using uracil (U) instead of thymine (T).
Three types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
mRNA carries instructions for protein synthesis from DNA.
rRNA is part of the ribosome and translates instructions for protein synthesis.
tRNA delivers appropriate amino acids to the ribosome.

Transcription: RNA is synthesized from a DNA template in the nucleus, using RNA polymerase.
The promoter region, including the TATA box, is crucial for transcription initiation.
Splicing: Introns (non-coding regions) are removed, and exons (coding regions) are retained in mRNA.
Translation: mRNA is used to synthesize a protein in the cytoplasm.
tRNA delivers amino acids to the ribosome according to the mRNA codon sequence.

Gene expression is the degree to which a gene is actively transcribed.
Induction increases gene expression, while repression reduces it.
Transcription factors regulate gene transcription by binding to specific DNA regions.

DNA is organized into chromosomes. Human somatic cells have 23 pairs.
22 pairs are autosomes, and the 23rd pair are sex chromosomes (XX for females, XY for males).
Mitosis duplicates somatic cells, each with 46 chromosomes (23 pairs).
Meiosis replicates germ cells, resulting in gametes with 23 single chromosomes.
A karyotype is a photographic arrangement of chromosomes.

Chromosomes are classified based on centromere position: metacentric, submetacentric, or acrocentric.
Chromosome arms are designated as p (short arm) and q (long arm).
Banding patterns are used to describe gene positions on a chromosome.

Genotype is the genetic information, while phenotype is the observable trait.
Alleles are alternate forms of a gene at the same locus.
Single-gene traits follow Mendelian laws.
Polygenic inheritance involves multiple genes.
Multifactorial inheritance includes both multiple genes and environmental factors.
Genetic imprinting: parental genomes do not contribute equally, affecting offspring development.

Family linkage studies: Genes close together on the same chromosome are likely to be inherited together.
Hybridization Studies: Somatic cell hybridization fuses cells from different species to map genes to specific chromosomes; In situ hybridization uses tagged DNA or RNA probes to detect gene locations.

The International HapMap Project developed a haplotype map of DNA sequence variations.
Single nucleotide polymorphisms (SNPs) are sites where people differ at a single DNA base.
A haplotype consists of closely linked SNPs passed as a block from one generation to another.

Recombinant DNA combines DNA molecules not found together in nature.
Restriction enzymes cut DNA at specific sequences for gene cloning.
Gene isolation and cloning produce copies of modified DNA.
DNA fingerprinting uses recombinant DNA technology for forensic analysis.
Gene therapy: Transferred genes can replace defective genes or inhibit deleterious genes; CRISPR-Cas9 technology edits genes by cutting out and replacing sections of the genome.

RNA interference (RNAi) suppresses gene expression by using small interfering RNA.
RNAi is used to target genes for therapeutic purposes.
Reverse genomics infers genes function through silencing its expression using RNAi.

Geriatric: Single-gene mutations influence aging; telomere shortening contributes to aging.
Pediatric: Chromosomal anomalies cause cognitive impairment and birth defects; newborn screening is used for inborn errors of metabolism; family pedigrees identify genetic disorders.