Ap Biology Practice Questions

     The process, during which the germ cells are generated is called meiosis. It represents nature's solution to the problem of chromosome doubling that would occur, if two diploid cells, i.e. two cells with a double set of chromosomes would fuse. Accordingly does meiosis produce haploid germ cells, with maternal and paternal germ cell fusing at fertilization and thus generating a

Later on a male and female haploid cell will join to form a diploid cell with the right number of chromosomes.

21) As sperm are produced, they go through several stages. Which stage develops directly into mature motile sperm?

A) Meiosis consists of two cell divisions and is broken up into Meiosis I and Meiosis II. At the beginning of the Cell Cycle, in this case there are four chromatids each from the homologous pairs being A, a, B, b. This is the Diploid number (4) meaning it is 2 times the haploid number that will be seen at the end of meiosis II. During the S phase of interphase, the chromatids replicate and reach the end of G2 phase. Now starting meiosis, during the first stage of prophase I the chromosomes condense and pair up through synapsis with their sister chromatids creating AA, aa, BB, bb. After they pair up they go through a process called crossing over, where the homologous chromosomes share a piece of their genetic material with each other. Crossing over allows for the genetic diversity of chromosomes. Now there are four homologous chromosomes Aa, Aa, Bb, Bb, each containing heterozygous alleles because the sister chromatids exchanged genetic information with their homologous pair. During late prophase I, spindle fibers being to form where they will later attach to a homologous chromosomes centromere. The next stage is Metaphase I. During metaphase I, the homologous pairs line up at the metaphase plate, also known to be the center of the cell. The homologous pairs form a tetrad which is considered a group of four homologous chromosomes. These homologous chromosomes orient themselves randomly, which is know as the process of independent

Fertilization in animals is similar to that in plants because its first cellcell change occurs after gamete fusion rises in the cytoplasmic Ca2+ levels as it does in animal gamete fusion. Also, the plants make a block to polyspermy, which is the fertilization of an egg by more than one sperm cell, as do the animal’s cell’s eggs.

Anaphase – the chromosomes are divided into single from pair and the chromosomes move to opposite poles

The structure formed by centrioles made up of microtubules that splits chromosomes during anaphase and pulls them toward opposite poles of the cell. During anaphase, it also helps to elongate the cell, in preparation for telophase.

[1] "Development of the embryo begins at Stage 1 when a sperm fertilizes an oocyte and together they form a zygote."

In the year 1882 a man by the name of Walter Flemmings found out the process of mitosis in greater depth. A German zoologist Otto Bütschli might have discovered a process known as "mitosis", nevertheless he wasn't able to explain the topic in understandable vocabulary. Originally mitosis was discovered in frog, rabbit, and cat cornea cells and described briefly by the Polish histologist Wacław Mayzel in 1875. Flemmings got the fame because of his explanation. Now most of you might not know what this is since it is fairly new. This is a process where body cells or somatic cells are produced concluding the end product to be identical to one another. This an asexual process of cell division. In other words mitosis is a part of the cell cycle

The proper division of cells is fundamental for growth and reproduction of organisms. Chromosomes must divide evenly and accurately between the two new cells so that harmful mutations are prevented from occurring. Cohesin is an important protein mediator in these precise divisive events. While preparing for mitosis, cohesin forms a ring around DNA to hold sister chromatids together in an organized fashion. Cohesin is comprised of 2 intramolecular coiled coil proteins, Smc1 and Smc3, which dimerize to form a circular protein. The dimerization domain of these proteins, also known as the hinge, keeps these proteins bound together. At the other end of cohesin, the ATPase head domains of Smc1 and Smc3 are held together by Scc1, a kleisin protein essential to the unloading of cohesin during anaphase. Scc1 is cleaved by separase once all chromosomes are attached to microtubules correctly and tension is sensed by the cell. Cleavage of Scc1 allows release of DNA from cohesin and separation of sister chromatids to opposite ends of the cell. The removal of cohesin from DNA is well studied and understood, but there is still controversy regarding the mechanisms of cohesin loading onto DNA.

fertilisation of the ovum takes place, however this happens as the expanded end, opening into the

Although fusion between two different chromosomes will not occur, following DNA replication but the loss of a single telomere can result in fusion of sister chromatids (Sabatier et al., 2005). This type of chromosome rearrangement is more difficult to monitor than ring or dicentric chromosomes, because sister chromatid fusions are not detectable by routine cytogenetic analysis. As first described by McClintock, sister chromatid fusion can result in prolonged CIN involving breakage/fusion/bridge (B/F/B) cycles. B/F/B cycles occur when the fused sister chromatids form a bridge during anaphase and then break when the sister chromatids are pulled toward the daughter cells during cytokinesis (John P. Murnane,

During a cell division, it is believed that genomic instability is minimized by four major mechanisms, which include chromosome segregation in

mitotic division and the daughter cells are pushed towards to surface so they can provide

The totipotent cells then turn into a blastocyst by many types of cell division, which forms a lot of cells in side.