An organism is heterozygous at two gene loci on different chromosomes. Explain how these alleles are transmitted by the process of mitosis to daughter cells. After mitosis the parent cell's genome is dividedninto two daughter cells. In most eukaryotes, the nuclear envelope that separates the DNA from the cytoplasm disassembles. The chromosomes align themselves in a line spanning the cell. As the cell elongates, corresponding sister chromosomes are pulled toward opposite ends. A new nuclear envelope forms around the separated sister chromosomes. As mitosis completes, cytokinesis is well underway. Explain how these alleles are distributed by the process of meiosis to gametes. Meiosis I separates homologous chromosomes, producing two haploid cells. During Prophase I, synapse and crossing over occurs.
During Metaphase I, Homologous pairs move together along the metaphase plate. In Anaphase I, Kinetochore microtubules shorten, severing the recombination nodules and pulling homologous chromosomes apart. In Telophase I, The chromosomes arrive at the poles.
Explain how the behavior of these two pairs of homologous chromosomes during meoisis provides the physical basis for Mendel's two laws of inheritence. The behavior of these two pairs of homologous chromosomes during meoisis provide the physical basis for Mendel's two laws of inheritence because the Law of Segregation states that when any individual produces gametes, the copies of a gene separate, so that each gamete receives only one copy--either one allele or the other. According to this "Inheritance Law," alleles of different genes assort independently of one another during gamete formation. Mendel concluded that different traits are inherited independently of each other, so that there is no relation. Heredity
A person with Turner's Syndrome has a genotype of XO, while a person with Klinefelter's Syndrome has a genotype XXY. Explain how these two mutations come about. Scientists understand that comparatively few genes are inherited in a simple Mendelian fashion. Pleiotropy
The production by a single gene of two or more unrelated effects. Epistasis
The interaction of genes that are not alleles, in particular the suppression of the effect of one such gene by another. Gene collaboration
Polygenic inheritance is the inheritance of quantitative traits influenced by multiple genes. Complementary genes
one of a pair of genes, each from different loci, that together are required for the expression of a certain characteristic Evolution
Explain Charles darwin's theory of evolution by natural selection. Natural selection states that evolutionary change comes through the production of variation in each generation and differential survival of individuals with different combinations of these variable characters. Individuals with characteristics which increase their probability of survival will have more opportunities to reproduce and their offspring will also benefit from the heritable, advantageous character. Each of the following refers to one aspect of evolution. Explain each in terms of natural selection. convergent evolution and the similarities amoung species in a particular biome When species live in the same biome, they have similar environments, similar habitats, and similar needs. Convergent evolution can cause unrelated species to evolve similar adaptations to fit these similar needs. speciation and isolation
Isolation is necessary for speciation to occur. After many generations the isolated population has accumulated so many differences that the two populations can no longer interbreed, even if they are in the same area. heterozygote advantage
Heterozygote advantage is when the heterozygotes have a better chance of surviving than either the homozygous dominant or homozygous recessive individuals. Sickle cell is an example of this. Immune System