1. The genome of an organism is inscribed in DNA, or in some viruses RNA. The portion of the genome that codes for a protein or an RNA is referred to as a gene. Those genes that code for proteins are composed of tri-nucleotide units called codons, each coding for a single amino acid.
2. Mechanisms of gene regulation include: Regulating the rate of transcription. This is the most economical method of regulation. Regulating the processing of RNA molecules, including alternative splicing to produce more than one protein product from a single gene.
Think of mitochondria as batteries that give a power boost to their host cell. without mitochondria modern cell would die for lack of an adequate energy supply.
Birds have a hard time in cold weather, because their body temperatures are higher than those of humans They provide warmth and insulation against colder temperatures. Many birds grow extra feathers in the months leading up to colder weather, so that they'll stay warmer when temperatures drop.
