a. Genotype/Phenotype. The genotype is the actual genetic makeup of an individual. The phenotype is the physical and functional makeup of an individual as determined both by the genotype and the environment.
b. Dominant/Recessive. Consider a gene in one set of chromo-somes and the corresponding gene in the other set. If one of the genes alone can produce a characteristic of the phenotype, the gene is said to be dominant. If both genes must be the same to produce a characteristic of the phenotype, then the genes are recessive. In a situation where one of the pair is dominant and the other is recessive, the dominant gene determines the ultimate characteristic.
c. Homozygous/Heterozygous. Again, consider a gene in one set of chromosomes and the corresponding gene in the other set. If the two genes are the same, we say that the individual is homozygous for that trait. If the two genes are different, we say that the individual is heterozygous for that trait.
d. Fraternal/Identical. In multiple births, two or more of the newborn may or may not resemble each other closely. They may resemble each other in sex (gender) and other physical and functional traits.
(1) If two of the individuals are different, they are called fraternal twins.
(2) If they closely resemble each other, they are called identical twins. Identical twins are believed to originate in a common zygote, which separates into two entities at a very early stage. Thus, identical twins have the same genetic makeup. However, one is often right-oriented and the other left-oriented.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.