Cell cycle and reproductionParts of the cell cycleThe cell cycle is made up of four main parts, G1, the G used to stand for gap, but now it stands for growth thanks to scientific discovery of what occurs in the cell during G phases, S, for DNA synthesis, G2, and M, for mitosis. In G1, the cell grows, and produces protein. In S, DNA is duplicated, in G2, the cell continues to grow and produce protein, the cell will not begin to split until it has enough protein. M is the most complicated phase, it is made up of tinier phases.
Prophase, where the membrane dissolves around the nucleus, and dna can survive in the cell naturally. Metaphase is when the chromatids, still paired up, line up in the center of the cell. Anaphase, when the chromatids split up into singular chromatids. Telophase, where the chromatids go to opposite sides of the cell and cytokinesis when the cells part from each other, and reform the nuclear membrane. During meiosis the cell goes through all of the phases again, except the chromatids can exchange parts, and there are four daughter cells with only one of each chromosome instead of two.How does the cell advance to the next stage When a cell completes a phase in the cell cycle, it does a form of check, to see if it is ready to duplicate. After G1 the cell checks if the DNA is stable, it checks if there are enough resources and protein to reproduce, and if the environment is safe.
G2 checks if the DNA was replicated correctly, and if all proteins are ready, there is no S checkpoint, and when the cells finishes S, it moves immediately to G2. The last checkpoint occurs after metaphase, and it checks to see if each sister chromatid has a spindle, which separates the two sister chromatids, a sister chromatid is two chromatids combined.Mitosis vs. Meiosis Mitosis and Meiosis are what differentiate sex cells and somatic cells.
Mitosis produces diploid, somatic daughter cells while meiosis produces haploid, sex daughter cells, and includes crossing over. During the second M phase, chromosomes swap genes, and go through the steps of Mitosis twice, except the steps happen a little differently. During meiosis, in the second phase of mitosis, the chromatids reform into sister chromatids, swapping parts and then they proceed to line up, and split, except with twenty three chromosomes in each daughter cell.HeredityHow does the cell receive its genes?Parents combine their sex cells to create a zygote, this zygote gets one of each chromosome, and they come together to make a somatic child cell. The cells in the parents are directly from their parents, so your genetics, actually come from your grandparents. The cell then undergoes mitosis, where the genetic information is doubled, then divided in two, over and over until a baby is formed, and can become a part of the world. An example of a mendelian gene passed on in animalsCystic fibrosis is an example of A mendelian gene, one that has a dominant and recessive trait.
Cystic fibrosis is recessive, and autosomal, meaning that it is not on the twenty third chromosome. Cystic fibrosis is a gene that causes bad salt regulation, and causes your sweat to be extremely sticky, as well as various internal organs such as the lungs, people with cystic fibrosis are prone to lung infections due to a warm moist environment being provided in the lungs in the form of mucus.Example of Incomplete dominance Horses are an example of incomplete dominance, when a white and black horse breed, they create a brown horse. Incomplete dominance occurs when two genes are incomplete, and mix with each other. Incomplete dominance is commonly seen in hair or skin color of many animals, human skin and hair is polygenic.Example of Codominance Cows are an example of Codominance when a white and red cow are bred, they create a roan cow, which has both types of fur colors. A codominant trait is where two traits both appear instead of dominant and recessive.
Codominance is also commonly seen in skin color, in spotted, or multi-color animals.Example of Multiple alleleHuman blood type is an example of a multiple allelic trait and codominance. Multiple allelic traits are when there are more than two alleles for a trait. There are three alleles for blood type, A, B, and O. The codominance part comes from A and B both showing up in AB types.
Other examples of multiple allelic traits would be texture of hair, and eye color in humans and cats.Example of Polygenic traitsHuman height is an example of a polygenic trait and incomplete dominance. Polygenic traits are when multiple genes exist that affect a trait. Height has three genes, similar to skin color, and each one mixes, three tall and three short traits would create a child equal to the average heightTypes of mutations, and how they happenWhen a gene is changed or passed down incorrectly, the person with the mutated gene will create incorrect proteins, and certain cells will not be able to function properly, unless the mutation is silent, a silent mutation still codes for the same amino acid when being translated. There are four main types of mutations, insertion is where one or more base pairs are added, a base pair refers to one bond of adenine and thymine or cytosine and guanine.
Deletion is when one or more base pairs are removed. Both of these mutations cause a frameshift, which means that protein pairs will all be messed up. The fourth type of mutation is replacement, when base pairs are replaced, this can still be just as bad, or have much less effect than a frameshift. Nondisjunction is when chromatids fail to separate and cause an uneven distribution among sex cells, this can lead to three or one chromosome,which can cause diseases such as down syndrome.