First Mr. Finley checked our homework on the meiosis worksheet, and the notes about crossing over. Then we discussed crossing over. Crossing over is when homologous pairs excange parts of their chromotids, or DNA so each haploid cell can become different. When the homologous pairs meet, it is called tetra. If homologous pairs cannot cross over, all sperm cells would be exactly the same. That is what the picture is about. The reason why you do not look exactly like your siblings is because the sperm cell that fertilized the egg with you was different then the sperm cell that fertilized the egg with your brother. These sperm cells were probably similar which is why you probably look similar to your brother. We also learned that identical twins are two sperm cells in one egg. The two sperm cells would be so similar, and the two new babies would both take the traits of that one egg. Furturnile twins are two sperm cells and two egg cells meeting. This forms two zygotes which means two babies that look very similar, but not identicle. So a very general reason for looking similar to someone would be different, but a similar zygote, (from the same parents). Also we talked about how meiosis creates haploid cells. haploid cells have fifty percent chromosomes, so when these cells mix with the opposite gender's reproductive cell which also has fifty percent chromosomes, merge and make one hundred percent chromosomes. With fifty percent chromosomes from the female and fifty percent chromosomes from the male.

Jordan Price