Biology First Midterm I
Terms
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- Principle of Independent Assortment
- Alleles of different genes are transmitted independently of each other.
- Principle of Segregation
- Alleles separate into different gamete cells during gamete formation Each gamete contains one allele of each gene.
- Incomplete Dominance
- heterozygotes have an intermediate phenotype. Four-O'clocks F1 generation consist of an intermediate phenotype
- Codominance
- Heterozygotes have the phenotype associated with both alleles present.
- Multiple Allelism
- The existance of more than two alleles of the same gene. Eg. human blood. has i, iA, iB to code for O, A, B, and AB
- Polymorphic
- When different combination of alleles produce more than two distinct phenotypes. A, B, O, phenotypes are produced by alleles i, iA, and ib
- Pleiotropic
- When a gene that influences many traits, rather than just one trait. Marfan syndrom (one gene causes distortion in height, limbs.. etc.
- Epistasis
- When types of gene interactions occur, the phenotype produced by an allele depends on the action of alleles of other genes. (occurs** when one gene affects the action of another gene) Colors of Bell peppers.
- Polygenic Inheritance
- Each gene adds a small amount to the value of the phenotype.
- Evolutionary Forces
- Natural Selection, Mutation, Genetic Flow, Genetic Drift.
- Natural Selection
- Increases the frequency of alleles that contribute to improved reproductive success. COntains (Directional selection, Stabilizing Selection, Disruptive Selection, Sexual Selection.)
- Genetic Drift
- Causes allele frequencies to change randomly Can cause deleterious alleles to become higher in frequency. Random with respect to fitness, most pronounced in small population, can lead to random loss or fixation of alleles. DECREASED GENETIC VARIATION WITHIN POPULATIONS AND INCREASED GENETIC DIFFERENCES BETWEEN POPULATIONS.
- Gene Flow
- Equalizes allele frequencies between the source population and the recipient population. When alleles move from one population to another, the population become more alike.
- Mutation
- Any change to the hereditary material of an organism. Produces new alleles. Increases Genetic Variation by new alleles. Random with respect to fitness.