Biology: Genetics and Pod Color Essay examples

2071 Words Apr 5th, 2011 9 Pages
BIOLOGY MIDTERM ESSAY

1. How does the biologist determine whether a thing is living or nonliving? Or what characteristics do living organisms have that non-living things do not?
They look at it under a microscope and see if it has cells. Basically, if it has cells the it's alive. If it doesn't have cells it is considered nonliving. There are smaller archaebacteria that behave like small parts of cells. These are considered living too, because they have chemical bonds of RNA, which is the singular shorter form of DNA. There is evidence that viruses change with different hosts, but they are generally considered non-living. They are much smaller chemical chains (with some form of movement and reproduction) and do not come from cells
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These were cross-pollination experiments with pea plants that differed in one trait, for example pod color.

Mendel began to wonder what would happen if he studied plants that differed in two traits. Would both traits be transmitted to the offspring together or would one trait be transmitted independently of the other? From his experiments Mendel developed the principle now known as the law of independent assortment.
Mendel's Law of Independent Assortment

Mendel performed dihybrid crosses in plants that were true-breeding for two traits. For example, a plant that had green pod color and yellow seed color was cross-pollinated with a plant that had yellow pod color and green seeds. In this cross, the traits for green pod color (GG) and yellow seed color (YY) are dominant. Yellow pod color (gg) and green seed color (yy) are recessive. The resulting offspring (Figure A) or F1 generation were all heterozygous for green pod color and yellow seeds (GgYy).
After observing the results of the dihybrid cross, Mendel allowed all of the F1 plants to self-pollinate. He referred to these offspring as the F2 generation. Mendel noticed a 9:3:3:1 ratio (Figure B). About 9 of the F2 plants had green pods and yellow seeds, 3 had green pods and green seeds, 3 had yellow pods and yellow seeds and 1 had a yellow pod and green seeds.
Mendel's Law of Independent Assortment

Mendel performed similar experiments focusing on several other traits like seed color and seed shape, pod