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Understanding Genetics: Mendel's Pea Plant Experiments

Explore Gregor Mendel's groundbreaking pea plant experiments that revolutionized the field of genetics. Learn about dominant and recessive traits, alleles, and Punnett squares.

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Understanding Genetics: Mendel's Pea Plant Experiments

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  1. GeneticsThe study of heredity http://cc040.k12.sd.us/PPTS/Intro%20to%20Genetics%20(2003).ppt#266,11,Mendel’s second cross

  2. Gregor Mendel • Born in 1822 in Czechoslovakia. • Became a monk at a monastery in 1843. • Taught biology and had interests in statistics. • Also studied at the University of Vienna. http://kentsimmons.uwinnipeg.ca/cm1504/mendel.htm

  3. Mendel (continued) • Upon return to the monastery, he continued to teach and work in the garden. • Between 1856 – 1863 he grew and tested over 28,000 pea plants. http://www.dnalc.org/view/16160-Gallery-2-Gregor-Mendel-s-Garden-Plot.html

  4. Mendel’s Peas Trait Dominant Recessive • Easy to grow. • Easily identifiable traits. • Can work with large numbers of samples. http://www.anselm.edu/homepage/jpitocch/genbio/geneticsnot.html

  5. Mendel’s Experiments • He first created “pure” generations. • Trait = a characteristic • Mendel studied 7 traits. • He crossed plants of contrasting traits • Ex: Green pea plants + Yellow pea plants • The offspring (new plants) were called the F1 generation. +

  6. What happens when pure yellow peas are crossed with pure green peas • All of the offspring were yellow. • Hybrids = the offspring from crossing parents with contrasting traits. Observations Pure Yellow Pure Green + Y Y y y Y y Y y Y y Y y P Generation All offspring are yellow hybrids (Yy) F1 Generation

  7. What did Mendel Find? A. Inheritance is determined by factors passed on from one generation to another. • Mendel knew nothing about chromosomes, genes, or DNA. Why? • These terms hadn’t been defined yet ---or seen!!

  8. What were Mendel’s “factors?” B. The “factors” are now called GENES. C. Each gene has different forms called ALLELES. 1. With the gene coding for pea color, yellow is one form or allele of the gene – and green is another allele of the gene. 2. Some alleles are DOMINANT and others are RECESSIVE. a. In the case of the peas, which color is Dominant & which is Recessive???

  9. Another way to show the breeding of a pea plant with yellow seeds and a pea plant with green seeds y y Y Yy Yy Y Yy Yy PUNNETT SQUARE Green seed color is a recessive allele, represented with a ‘y’ Green Pea ‘mother’ Yellow Pea ‘father’ In all possible combos of alleles, the offspring will be yellow hybrids (Yy) Yellow seed color is a dominant allele, represented with a ‘Y’

  10. Observations Hybrid Yellow Hybrid Yellow + Y y Y y Y Y Y y y Y y y F1 Generation F2 Generation Mendel’s 2nd Cross He allowed the F1 generation to self-pollinate (breed with each other) to produce the F2 generation. Results: ¾ chance of having yellow offspring, ¼ chance of having green offspring Also, ¼ chance purebred Yellow, ½ chance Hybrid Yellow, ¼ chance purebred Green

  11. Another way to show the 2nd crossing F1 Hybrid ‘mother’ F2 Generation: Y Y = purebred yellow Y y = hybrid yellow y y = purebred green - OR - 75% yellow 25% green Y y Y y F1 Hybrid ‘father’ Purebred = HOMOZYGOUS; Hybrid = HETEROZYGOUS

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