Introduction to Genetics The Work of Gregor Mendel.
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Transcript of Introduction to Genetics The Work of Gregor Mendel.
![Page 1: Introduction to Genetics The Work of Gregor Mendel.](https://reader036.fdocuments.net/reader036/viewer/2022082612/56649f215503460f94c39c20/html5/thumbnails/1.jpg)
Introduction Introduction to Geneticsto GeneticsThe Work of Gregor MendelThe Work of Gregor Mendel
![Page 2: Introduction to Genetics The Work of Gregor Mendel.](https://reader036.fdocuments.net/reader036/viewer/2022082612/56649f215503460f94c39c20/html5/thumbnails/2.jpg)
Genetics• Scientific study of heredity
• Gregor Mendel–Born in 1822 in Czech Republic
–Worked in monastery garden while teaching H.S. (math & science)
–Worked w/ true-breeding pea plants• If allowed to self-pollinate, produce offspring identical to themselves
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Genes and Dominance
• Mendel studied 7 traits–Specific characteristic that varies
from one individual to another– color, height
–Each trait had two contrasting characters – greed seeds vs. yellow
–Crossed true-breeding plants of each type to opposing character
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• True-breeding yellow seed X True-breeding green seed
• Original pair of plants = P (parental) generation
• Offspring = F1 (first filial)
• Offspring of crosses between parents w/ different traits = hybrids
Genes and Dominance
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• What did the F1 hybrids look like? Did they look like a blend of both parents? No!
• All F1 offspring only showed the character of one parent.
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Mendel’s Two Conclusions
• 1. Biological inheritance is determined by factors that are passed on from one generation to the next–Genes – chemical factors that determine traits
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• Each trait that Mendel studied was controlled by one gene that occurred in two contrasting forms–Ex: Gene for Plant Height = One form for tall one for short
• Alleles – different forms of a gene
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• 2. Principle of Dominance – some alleles are dominant and others are recessive–If there is a dominant present, that form is shown
–If there are two recessive present, the recessive is shown
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Segregation• Did the recessive alleles disappear,
or were they still present ?–To find the answer, he allowed F1
generation plants to self-pollinate to create an F2 generation
• What happened? –Traits reappeared. ¼ of the F2
plants showed the recessive allele
![Page 11: Introduction to Genetics The Work of Gregor Mendel.](https://reader036.fdocuments.net/reader036/viewer/2022082612/56649f215503460f94c39c20/html5/thumbnails/11.jpg)
Segregation, cont’d
• Law of Segregation–Two alleles separate from each other so that each gamete carries only a single copy of each gene
–Ex: Fig. 11-5
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Introduction Introduction to Geneticsto Genetics
Genetics and Genetics and ProbabilityProbability
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Genetics and Probability
• Probability–The likelihood that a particular event
will occur• Ex: tossing a quarter
–Heads = 1 in 2
–Tails = 1 in 2
–3 tails in a row ½ x ½ x ½ = 1/8
–Principles can be used to predict outcome of genetic crosses
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Genetic Vocabulary
• Character– Detectable
inheritable feature of an organism
• Trait– Variant of inheritable
character
= allele / alleles
• Dominant– Capital letter (SS)
• Recessive– Lower case (ss)
• Two alleles for each character– Mom and dad
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Genetic Vocabulary
• Genotype–The genetic makeup of an organism
–Written in letter format
–PP, pp, Pp
• Phenotype
–The physical traits of an organism
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Genetic Vocabulary
• Homozygous–Having two
identical alleles for a given trait• PP
• ss
• Heterozygous–Having two
different alleles for a given trait• Pp
• Ss
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Basic Crosses
![Page 18: Introduction to Genetics The Work of Gregor Mendel.](https://reader036.fdocuments.net/reader036/viewer/2022082612/56649f215503460f94c39c20/html5/thumbnails/18.jpg)
Recessive/Dominant
• action items required of you