gregor mendel & basic genetic principles. who is gregor mendel? austrian monk that experimented...
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Gregor Mendel &
Basic Genetic Principles
Who is Gregor Mendel?
• Austrian Monk that experimented with pea plants.
• He discovered the basic principles of genetics.
Pea Plants
• Pollination occurs easily within the flower.
• Relatively short life cycle (2-3 weeks).
• Have 7 characteristics with contrasting forms.
Pollination
• Movement of pollen between sexual parts of flowers.
• Self Pollination – pollination that occurs within one flower.
• Cross Pollination – movement of pollen from one flower to another.
7 different traits of pea plants
• Seed shape – round/wrinkled
• Seed color – yellow/green
• Seed coat color – colored/white
• Pod shape – inflated/constricted
• Pod color – green/yellow
• Flower position – axial/terminal
• Stem length – long/short
Mendel’s 1st Experiment
• Mendel created pure–bred pea plants of each characteristic.
Ex. Tall/Short, Green seeds/Yellow seeds.
• He crossed these plants together (P1 or Parent generation).
• Offspring: ALL TALL! (F1 generation).
Mendel’s 1st LawLaw of Dominance
• When organisms with contrasting traits are crossed, only the Dominant trait appears in the offspring.
Mendel’s 2nd Experiment
• Mendel took those F1 generation plants and crossed them.
• F2 generation results: 3 TALL, 1 SHORT = 3:1 phenotypic ratio.
• 1 TT, 2 Tt, 1 tt =1:2:1 genotypic ratio
Mendel’s 2nd LawLaw of Segregation
• Factors occur in pairs and separate during gamete formation only to recombine again during fertilization.
Vocabulary
• Dominant gene – gene that prevents the expression of another. Ex. Brown hair – represented with a capital B.
• Recessive gene – gene that is not expressed, it is usually hidden by a dominant gene. Ex. Blond hair – represented with a lower case b.
• Allele – dominant and recessive forms of genes.
• Genotype – genetic makeup of an organism regarding its characteristics.(TT, Tt, tt)
• Phenotype – physical appearance of an organism. (Tall/Short)
• Heterozygous – have 2 different alleles for a particular charateristic. (Ex. Tt = a heterozygous tall plant)
• Homozygous – have the same alleles for a particular characteristic. (Ex. TT = a homozygous tall plant & tt = a homozygous short plant)
• Hybrid – Common term for heterozygous. Ex. Tt
• Monohybrid Cross – Cross between two parents that deals with only one trait.
• Dihybrid Cross – Cross between two parents dealing with two different traits.
• Incomplete dominance – Blending, when both traits express themselves.
• Sex linked traits – Involves genes that are located on the X chromosome.
Figure 10.13
Figure 10.13
figure 10-13.jpg
Mendel's law of independent assortment of alleles
• Alleles of different genes are assorted independently of one another during the formation of gametes.
• Mendel determined this law by crossing plants containing two different traits. (Ex. True breed round & yellow seeded plants (RRYY) with true breed wrinkled & green seeds (rryy)
Figure 10.7
Figure 10.7
figure 10-07.jpg