Genetics

DNA, Genes, Chromosomes

Genetics Genetics ~ the study of heredity, how traits are passed from parents to offspring Gene ~ a section of DNA that produces a particular polypeptide chain of amino acids (a protein or section of a protein) that causes a particular trait. Characteristic potentials are determined by the genes, but the extent to which they are expressed depends on the behavior and environment of the individual.

DNA molecule = Sentence Genes = Words Nucleotides (with different bases) = Letters

Mechanism of Genetic Inheritance Chromosomes ~ long strands of DNA and the proteins associated with them. Histones ~ proteins with the DNA: Help support and protect the DNA strands Aid in replication and transcription In a nondividing cell, the chromosomes look like a tangled mass in the nucleus, which is referred to as chromatin material.

The shape of a chromosome that is most familiar is one that is already duplicated and ready for cell division. Chromatid (sister chromatids) ~ each DNA duplicate produced through the process of replication, that are joined at the centromere. Centromere ~ constricted area in the center of duplicated chromosomes.

The number of chromosomes is determined by the species The number of chromosomes is determined by the species. Most humans have 46 chromosomes, or 23 pairs. The number of chromosomes is not determined by the size of the organism.

Karyotype ~ a picture or illustration of the chromosomes of a cell that are arranged according to their size. The chromosomes occur in pairs, and are numbered, starting with the largest.

Homologous pairs of chromosomes ~ two chromosomes that have variations of the same genes in the same order. Homologue ~ each member in a homologous pair. Diploid ~ cells that have homologous pairs of chromosomes. Abbreviated 2n. For humans the diploid number is 46 (2n = 46) Haploid ~ only one chromosome from every pair for that species. Humans 23 (n = 23)

Replication Replication is simply copying of the DNA. It must be done before a cell can divide.

Transcription and Translation These processes are how you get from DNA sequence which contains genes to proteins which result in different characteristics. The sequence of bases in the DNA is unique for each person, which leads to different proteins being produced, which gives each person unique characteristics. The base sequence in DNA determines the base sequence in RNA (transcription), and the RNA sequence determines the amino acid sequence which makes up the protein (translation).