Ap Biology Exercise 2

Chromosome pairs line up across the equator of the spindle at metaphase I (5). In anaphase I the chromosomes separate and travel to opposite ends of the spindle. The chromosomes migrate to the equators of two new spindles for metaphase 2 (7). Next the chromatids are pulled apart in anaphase 2 to form four clusters of chromosomes in telophase 2. The nuclear envelopes reform around four haploid nuclei that will give rise gamete

According to the data table, prophase is the longest stage of mitosis. Even though there were more tallies in the interphase section, interphase is not considered a stage of the mitotic cycle; it is more or less considered a stage in the cell cycle. Telophase is the shortest stage because there were very few cells that showed evidence of them actually being in this stage. Metaphase and anaphase are intermediate stages, with metaphase being longer than anaphase.

These bivalents line up along the equator during metaphase I, the arrangement of the bivalent is completely random and relative to the orientation of the other bivalents, this is known as the independent assortment of chromosomes. This is followed by anaphase I where the homologous chromosomes separate and move to the opposite poles of the cell. At telophase I the cell divides into two, each cell contains one chromosome from each homologous pair. The second stage of meiosis is similar to mitosis.

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

Hypophosphatemia (vitamin D-resistant rickets) is inherited as an sex-linked dominant trait. The relevant gene is found on the X chromosome

2. In which phases of mitosis are sister chromatids visible, and attached to each other at the centromere?

Although mitosis is just a fraction of time compared to interphase it can be divided into four distinct subphases. If we start viewing a cell under a brightfield microscope right at the end of interphase subphase G2 we would see that throughout the interphase process (fig 1) the cell has grown considerably in size due to production of extra mitochondria and endoplasmic reticulum. The cell has also gone through the labor of duplicating all of its chromosomes, a process known as DNA synthesis. Now that the cell has made all of these preparations it's time to start prophase (fig 2), the first stage of the mitotic phase. This stage is visibly identified by the chromatin becoming the tightly formed chromosomes. During the lab we were able to view these newly formed chromosomes best on the onion root tip

C. A chromatid is a chromosome that has been replicated but has not yet separated from its sister chromatid.

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

Then multiply this fraction by the total time (720 minutes) needed to complete one mitotic division. In other words, the time for a specific phase is equal to:

19) The phase of mitosis during which the nuclear envelope fragments and the nucleoli disappear is called

cell will look just like any other 'normal' cell although this is far from the

It is expected that the most common phase of mitosis seen will be interphase as the cell spends around ninety percent of its time in this phase. This is because interphase is the period between cell division in which the cells grows, DNA replicates and centrioles divide. It is such a long phase that it is even split into three sub-phases; G1 phase in which a cell grows, S phase or synthesis, in which a cell copies its chromosome and G2 phase in which the cell grows further and prepares for division.

There are four stages of mitosis. The first stage is the prophase. In this stage the chromosomes become

The two alleles, one contributed by the male and the one by the female gamete remain distinct; alleles do not blend with one another or become altered in any other way