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Child Development - Sara Carlson Psych107 Written...

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Sara Carlson Psych107 Written Assignment: Producing New Life Childbirth is a very complex phenomenon. The process begins with fertilization, and from the moment the sperm reaches the egg, growth and change are happening at a rapid pace. We all start out as a tiny ball of cells, formed by the compilation of our parents’ DNA. But how does this happen? How is it that one sperm and one egg form a completely unique individual? To answer this we need to study the genetic foundations, prenatal development, childbirth and the first phase in the human child’s life. Our genetic material is made up of deoxyribonucleic acid (DNA), which is stored as compact chromosomes in the nuclei of each one of our cells. The human genome is made up of 23 pairs of chromosomes and each of these chromosomes contains several genes. Our genes give us our unique characteristics and traits, which depend on allele dominance. We obtain one allele from each of our parents, and the set of two alleles is called the genotype. In dominant-recessive inheritance, dominant alleles are always shown in the phenotype of an individual, and recessive alleles are shown when the individual is homozygous recessive. If an individual is heterozygous they have a dominant allele and a recessive allele, and the dominant allele determines the phenotype but they are “carriers” of the recessive allele. There are also different modes of inheritance such as codominance, in which both the recessive trait and the dominant trait are displayed equally. An example of this is sickle cell trait which affects carriers of the recessive sickle cell anemia allele. In many cases, one gene does not code for one trait. Polygenic traits involve multiple genes that together form a phenotype. The phenotype of an individual is an observable characteristic, and it is dependent on the genotype. Our genetic material has the ability to replicate itself during the process of mitosis. During mitosis the DNA is replicated and then the cell divides so that there is exactly one copy
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of each chromosome in each daughter cell. Sex cells, called gametes, go through a different process. Gametes are haploid cells, meaning they have only 23 chromosomes, and they are the result of meiosis. During meiosis the DNA is replicated but the cell undergoes division twice. In the first division a process called crossing over increases variance in the combinations of alleles given to each daughter cell. Meiosis produces four daughter sperm cells in males, but in females one egg is produced that includes all of the cellular organelles, and the other three daughter cells are barr bodies. The sex cells contain 23 chromosomes, including one sex chromosome. Each of these cells has half of the parent cell DNA, and when the egg is fertilized by a sperm it forms a zygote with 46 chromosomes. Females have two X chromosomes and males have an X and a Y
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