Psych 3 Reading

Psych 3 Reading - Psych 3 Reading after Midterm p 19-26...

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Psych 3 Reading. ( after Midterm) p. 19-26 Mendelian genetics : -studied inheritance in pea plants. Dichotomous traits are traits that occur in one form or the other, not normally in combination. Ex) seed color, either brown or white seeds. True breeding lines are lines in which interbred members always produce offspring with same strait like brown seeds generation after generation. -mendel crossbred offspring of pea plants that had brown seeds with those that had white seeds. The offspring of this cross all had brown seeds, Then he bred the 1 st generation offspring with one another and ¾ had brown seeds and ¼ had white seeds. Each time he repeated the experiment he got the same results. - an organisms observable traits are its phenotype -the traits that it passes on to its offspring through genetic material is its genotype -Mendels four ideas: 1. there are 2 kinds of inherited factors for each dichotomous traits, for ex- that a brown seed and a white seed factor control seed color. 2. each organism possesses 2 genes for each of its dichotomous traits, for ex each pea plant has either two brown seeded genes, two white seeded genes or one of each. 3. one of the two kinds of genes for each dichotomous trait dominates the other in heterozygous organisms 4. for each trait each organism randomly inherits one of its fathers two factors and one of its mothers two factors. Chromosomes and Reproduction - genes are located on chromosomes, threadlike structures in the nucleus of each cell. - Chromosomes occur in pairs, each species has a characteristic number of pairs in each of its body cells, humans have 23 pairs. - Process of cell division that produces gametes ( egg and sperm cells) is called meiosis. - In meiosis the chromosomes divide, and one chromosome of each pair goes to each of the two gametes that result from the division, and as a result, each gamete has only half the usual number of chromosomes; and when a sperm and egg cell combine during fertilization, a zygote with the full complement of chromosomes is produced. - All other cell division in the body occurs by mitosis. Just prior to
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mitotic division, the number of chromosomes doubles so that when the division occurs both daughter cells end up with the full complement of chromosomes. - Sperm and egg cells are created by meiotic division, the zygote grows with mitotic devision., mitotic division ovvurs over and over until an adult organism is created. - Meiosis accounts for much of the genetic diversity within each species. In humans, each meiotic division produces two gametes; each gamete contains one chromosome from each of the 23 pairs contained in each body cell. Because each of the 23 pairs is randomly sorted into the two gametes each human can produce gametes with 2^23 different combinations of chromosomes. Sex Chromosomes and Sex-linked traits
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Psych 3 Reading - Psych 3 Reading after Midterm p 19-26...

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