Show Menu

AP Bio Unit 5 Cheat Sheet by

AP Bio Unit 5 Cheat Sheet

5.1 Meiosis

Meiosis - a type of cell division that results in four daughter cells each with half the number of chromo­somes of the parent cell. During the process of meiosis, each sex cell only contains n amounts of chromo­somes, so that the resulting gamete would be 2n, or a diploid cell. Meiosis consists of two steps: Meiosis l and Meiosis ll.
Meiosis l Prophase l - the first phase in meiosis l where chromo­somes condense, homologous chromo­somes pair up to form tetrads, and crossing over occurs. Metaphase l - homologous (pairs of mother and father chromo­somes) align at the equator of the cell. Anaphase l - homologous chromo­somes seperate and move towards opposite poles of the cell. Telophase l - divided genetic material gathers at both poles forming two new cells.
Meiosis ll Prophase ll - chromo­somes condense and become visible while spindle fibers form and attach to these chromo­somes. Metaphase ll - chromo­somes align at the equator of the cell before they are pulled apart. Anaphase II - the sister chroma­tids, now individual chromo­somes, separate and move towards opposite poles of the cell. Telophase ll - the final phase in meiosis where nuclear membranes form around each set of chromo­somes, which decondense back into chromatin. The cytoplasm then divides resulting in four haploid daughter cells.

5.2 Meiosis and Genetic Diversity

Crossing over - a process that occurs during meiosis where two chromo­somes pair up and exchange segments of their genetic material.
Indepe­ndent Assortment - a principle stating that genes for different traits can segregate indepe­ndently during the formation of gametes.
Random Fertil­ization - each sperm and egg combin­ation is unique due to indepe­ndent assortment and crossing over during meiosis
Nondis­jun­ction - occurs when chromo­somes fail to separate properly during meiosis, resulting in gametes with an abnormal number of chromo­somes.

5.3 Mendelian Genetics

Gregor Mendel - 19th century scientist and Augustan friar who is best known for his experi­ments with pea plants that laid the foundation for the source of genetics.
Law of Segreg­ation - states that the two alleles from each parent are segregated during gamete formation. each gamete gets only one of the two copies of the gene.
Law of Indepe­ndent Assortment - states that the two alleles get split up without regard to how other alleles get split up.
Punnet Squares - a diagram used by biologists to predict the outcome of a genetic cross. shows all possible combin­ations of alleles that can result from a genetic cross.
Sex-linked traits - genes that are located on the sex chromo­somes (X and Y in humans). their expression can result in traits that differ between sexes.

5.4 Non-Me­ndelian Genetics

Multiple alleles - occur when there are three or more variations of a particular gene present within a popula­tion.
Incomplete dominance - a form of interm­ediate inheri­tance in which one allele for a specific trait is not completely expressed over its paired allele. this results in a third phenotype, where the expressed physical trait is a combin­ation of the phenotypes of both alleles.
Co-dom­inance - both alleles are equally dominant (WW, RR)

5.5 Enviro­nmental Effects on Phenotype

Enviro­nmental conditions - all external factors influe­ncing the life and develo­pment of an organism.
Selective pressure - an enviro­nmental factor that causes certain traits to be more or less advant­ageous, leading to changes in the frequency of those traits over genera­tions.
Phenotypic plasticity - the ability of an organism to change its phenotype in response to changes in the enviro­nment.

5.6 Chromo­somal Inheri­tance

Chromo­somes are inherited from both parents following the rules of genetics. There is an equal chance that either version of a gene may be inherited in offspring due to the law of indepe­ndent assort­ment. random fertil­ization allows for even more variation in that it is simply by chance that a certain egg and a certain sperm combine to form a zygote.
Crossing over in the first stages of meiosis leads to number of different chromo­somal combin­ations that increase the amount of variety in a popula­tion.

Punnet Square

Meiosis l

Meiosis ll

Indepe­ndent Assortment




No comments yet. Add yours below!

Add a Comment

Your Comment

Please enter your name.

    Please enter your email address

      Please enter your Comment.

          Related Cheat Sheets

          Properties of water Cheat Sheet