Mitotic Cell Division AND DNA Replication

Correctly indicate the direction of dna polymerase activity (ie the direction in which the new strand of DNA is synthesized) in a replication fork that has the 5' and 3' ends of each strand labeled.

-DNA replication begins at specific sites, called the origin of replication. DNA elongation and replication is catalyzed by DNA polymerase as nucleotides align w/ complementary bases along the template strand, they are added by DNA polymerase to growing end of DNA strand. -Replication bubble is formed by the replication fork where the leading and lagging strand join. (y shaped) -DNA polymerase synthesizes in the 5'-3' end ONLY!! Nucleotides are added along the 3' end

Explain How mitotic cell division produces two genetically identical cells

-During S phase each chromosome replicates, called sister chromatids. These identical sister chromatids are split apart during anaphase and become a chromosome in its own right. The result is two nuclei, identical to each other and to the original nucleus

Explain structural differences between a chromosome in G1 and the Same Chromosome in G2

-G1 phase: chromosomes have ½ the number of DNA than those in G2. the chromosomes uncoil. -G2 phase: the chromosome has been replicated. there is 2x as much dna in the chromosome.

List reasons cells divide

-Growth -Replication or reproduction -Repairment of dead or lost cells

Explain how the structure of DNA is important to a cell's ability to make an exact copy of chromosomes.

DNA Is double stranded, these two the complementary base pairings allow the DNA to make exact copies of itself. It's done so in a semi conservative replication. This means the dna molecule will separate during replication and each strand is used as a template for the synthesis of a new strand. The result is a new strand of DNA. (ends up w/ one original strand and one new strand.)

Explain the structural relationships among a double-stranded DNA molecule, a chromosome, a replicated chromosome, and sister chromatids.

DNA is contained within the chromosome. A chromosome is replicated which results in two identical copies, a sister chromatid. The sister chromatids are joined together by the centromere to create a chromosome with double the amount of dna.

Explain how the mechanism of DNA polymerase causes one strand of DNA to be replicated more rapidly (the leading strand) than the other (the lagging strand).

DNA polymerase can only synthesize in the 5'-3' direction. As the other strand runs antiparallel and creates a loop around the replication fork.

Describe what happens during G1, G2, S (and G0) phases of interphase and during mitosis and cytokinesis of M Phase.

G1 phase: -Chromosomes are uncoiled in the nucleus, Growth of the cell, and replication of proteins and organelles in the cell. S phase: -Synthesis of DNA; each chromosome duplicates to produce 2 sister chromatids. (The cell now has a double set of instructions/DNA for cellular activities). -The chromatids of each original chromosome are uncoiled in the S phase but are attached to each other at the centromere. G2 Phase: -Growth and preparation of the cell, enzymes are also made. Chromatids are involved in setting up machinery for mitosis. G0 phase -Period in which the cell is not dividing nor preparing to divide. Cell is in an inactive or dormant state. Ie; muscle cells, nerve cells for example do not replicate.

Describe the formation of a phosphodiester bond between 2 nucleotides.

Linkage between 3' carbon atom of one sugar molecule and the 5' carbon atom of another, (Deoxy)ribose. Strong covalent bonds form between the phosphate group and two 5-carbon ring carbohydrates (pentoses) over two ester bonds. This creates the backbone of dna and prevents it from degradation.

Identify the stage of mitosis based on the visibility and arrangement of chromosomes.

Prophase: Preparation phase. The chromosomes are most visible in this phase. The nuclear envelope disappears Metaphase: alignment phase. Chromosomes align along the metaphase plate. The centromere of each chromosome lies metaphase plate. Spindle fibers are responsible for the alignment Anaphase: separation and migration phase: spindle fibers pull the chromatids of each chromosome apart, to opposite poles. Each sister chromatid becomes a chromosome in its own right Telophase: Reconstruction phase. Chromosomes group themselves around poles. Chromosomes become longer and thinner until they appear more as chromatin. The nuclear membranes reform and nucleoli reappear. Cytokinesis also occurs during this time In plant cells a cell plate forms which separate the two new nuclei. The plate will become the cell wall separating the 2 daughter cells. -Animal cells cleavage furrow near the old metaphase plate pinches the parent cells in two, resulting in 2 new daughter cells.

Predict the effect on M phase if the function of actin microfilaments is disrupted.

The cell can't split apart because the contractile ring would not form during cytokinesis

Predict the effect on the M phase if the function of microtubules is disrupted

The chromosomes would not be able to be separated to their respective poles and mitosis could not be completed.

Explain why the two strands in a DNA molecule are antiparallel.

They allow for the formation of hydrogen bonds between the nucleotides adenine, guanine, cytosine, and thymine. If the strands were not antiparallel the non-symmetrical hydrogen bonding interactions would not be possible. Each base pair has specific pairings A-T have a double hydrogen bond while C-G have triple hydrogen bonds.