“Every aspet of an organism is determined or influenced by the genes of the organism” What genes are, what they do, how they interact with eachother and the enviroment to generate a phenotype.
Genes are segments of DNA that code for proteins or RNA molecules. These genes are the genetic material that is passed down from generation to generation in all species. The individual DNA segments each individual carries are known as their alleles or genotype. When two alleles are identical they are homozygous and when they are different they are heterozygous. These alleles are expressed physically through what is known as the phenotype. An example of a phenotype of a gene is hair color, which may be blond or brown.
In humans, a zygote starts out with a complete set of genes from its mother and father. The DNA is transcribed or copied into RNA sequences known as mRNA. These mRNA sequences are translated to make proteins. These proteins then dictate which chemical proceses will take place in the zygote’s development. The physical traits that are expressed or visibly seen are determined by which genes or alleles actually get expressed in the genome. At the beginning of life, all genes are turned on, then they are selectively silenced. The phenotype is generated throughout the life of organism. The genes carry the codes that make enzymes that carry all the molecular processes in a living organism. The proteins made then determine the phenotype. However, the phenotype is overall determined by three things, an individuals alleles or genes, their enviroment and randomn life processes.
For example, there can be incomplete dominance where there is a mix of alleles, where neither is dominant. An example, is a Red flower and a white flower that mate and make a pink flower.
Codominance is where both alleles are expressed but not blended.
Genes can be affected by enviroment and mutation. For example, height is affected by many factors like genes for growth, muscle tone, hormones and are also affected by the enviroment and nutrition available. These affects will then be seen in the physical expression of the affects on the gene.
Certain genes are dependent on other genes to be expressed.