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Mendel and His In-Gene-ius Idea…
Big Idea 3: Living systems store, retrieve, transmit, and respond to info essential to life processes.
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Essential Knowledge 3A3: The chromosomal basis of inheritance provides an understanding of the pattern of passage of genes from parent to offspring.
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… “particulate” hypothesis is the idea that parents pass on discrete heritable units (genes)…
Gregor Mendel
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Mendel’s Peas… Planned experiments using characters (flower color) and traits (purple/white)
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He Experiments… Mendel mated 2 contrasting, true-breeding varieties hybridization True-breeding parents = P generation Hybrid offspring of P generation = F1 generation When F1 individuals self-pollinate = F2 generation is produced
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Purple = dominant White = recessive 3:1 Ratio
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Mendel’s heritable factor = gene Alternate versions =alleles
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IA Video
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Law of Segregation and I.A. apply to genes on diff. chromosomes.
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Genes near each other on same chromosome tend to move as a unit
Probability of segregation is a fxn of the distance b/t them.
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Dominant vs Recessive Use Punnett Squares to predict heredity outcomes. Dominant alleles: Use upper case. Ex: S Recessive alleles: Use lower case. Ex: s
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Homozygous: alleles for a trait are same
Homozygous: alleles for a trait are same. Ex: SS or ss or TT (true breeding) Heterozygous: alleles for a trait are different. Ex: Ss or Tt
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Ratios Receive 2 types of info: genotype and phenotype.
Genotype: genetic trait that you cannot see (genes) Phenotype: trait or behavior you can see physically.
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Genotype Phenotype Use probability to analyze passage of single gene traits from parent to offspring
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Punnett Squares!!
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One Factor Punnett Square
One trait = monohybrid cross. Ex: Cross a tall dominant homozygous pea plant (TT) w/ short recessive homozygous pea plant (tt).
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Monohybrid Cross TT is a parent who is Tall
tt is a parent who is Short Both are homozygous that make heterozygous offspring.
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Ratios to Know TT x tt = 100% Dominant, but heterozygous
Tt x Tt = 75% Dominant, 25% Recessive, 3:1
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Two factor Punnett Square
Cross 2 traits = dihybrid cross. Example: Cross a dominant green, smooth pea plant (GGSS) with a recessive yellow, wrinkled pea plant (ggss)
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Ratios to Know SsTt x SsTt = 9:3:3:1 9 dominant in both traits
3 dominant in one trait or the other trait 1 recessive for both traits
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Human Genetic Disorders
Can be received by inheriting a single gene trait or specific chromosomal change Ex: Tay-Sachs Disease: Mutation on Chrom causing deterioration of nerve cells.
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What’s This??
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Punnett Square Sample Probs
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