G Chapter 2 - Chapter2 ,yourhair,eyeandskincolor...

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Chapter 2 Genes are the basic units of biological information Genes are passed from one generation to the next underlying the formation of every heritable trait Traits – the tendency to lose hair as you age, your hair, eye and skin color Heredity is the way genes transmit physiological, anatomical & behavioral traits from parents to offspring We start with a single fertilized egg cell that develops by division and differentiation into a   mature adult  Gregor Mendel examined alternative traits in pea plants (purple vs white flowers or yellow vs green seeds) This allowed him to make predictions about which traits would appear, disappear and then  reappear and in which generations  Genes are considered today as a region of DNA that encodes a specific protein or a particular type of RNA  Four Themes from Mendel’s Work 1. Variation, as expressed in alternative forms of a trait is widespread in nature Genetic diversity provides raw material for the continuously evolving variety of life we  see around us 2. Observational Variation is used to follow genes from one generation to the next  3. Variation inherited to genetic laws  4. Heredity applies to sexually reproducing organisms from protozoans to peas to people  2.1 Background: The Historical Puzzle of Inheritance  Artificial Selection Was the First Applied Genetic Technique  Artificial Selection – purposeful control over mating by choice of parents for the next generation  Ex: the domestic dog slowly arose from ancestral wolves  Farmers carried out artificial selection of plants by storing seeds for the next planting obtaining  strains that grew better as well as produced more. Weedlike plants turned into rice, wheat, and barley in Asia.  In America, plants turned into corn, squash, and tomatoes.  Plant breeders were then able to recognize male and female organs in plants.  Desirable Traits Sometimes Disappear and Reappear  Using strains, breeders could produce plants or animals with desired characteristics for food and  fiber however; they could not predict why a trait would sometimes disappear and then reappear.  Mendel Devised a New Experimental Approach  Mendel chose a garden pea as his experimental organism. Peas with male and female organs were able to  self fertilize (both eggs and pollen come from the same plant). The peas were cross fertilized instead of self fertilized. Cross fertilization is the ability for two individuals to brush pollen from one plant onto a female  organ of another plant. Mendel obtained a large number of individuals within a short growing season for  each successful generation.  Secondly, Mendel examined the inheritance of particular traits (purple vs. white flowers or yellow vs. green
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