# Why do we look similar to but different than our biological siblings?

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Why do we look similar to but different than our biological siblings?
Mendelian Genetics Why do we look similar to but different than our biological siblings?

Possible Results of Crosses
OR OR How is this possible? Can we accurately predict the outcome of crosses?

Heredity Vocabulary Homozygous = when an organism has two identical alleles for a particular gene Ex: GG (both dominant) or gg (both recessive) Heterozygous = when an organism has different alleles for the same gene Ex: Gg (one dominant and one recessive)

Heredity Vocabulary Genotype = genetic makeup (the combination alleles) Phenotypes = physical traits For each plant below, list all possible phenotypes and genotypes: Phenotypes: Yellow Green Genotypes: gg GG or Gg

Probability Mendel kept getting consistent results for particular crosses 64 green 48 green and 16 yellow

Probability Principles of probability can be used to predict the outcomes of genetic crosses Probability= likelihood that a particular event will occur What is the probability of the coin landing heads up?

Using Segregation to Predict Outcomes
G = green allele (dominant) g = yellow allele (recessive) Gg Gg Meiosis occurs G g G g Sex cells are produced with one allele each

Using Segregation to Predict Outcomes
Fertilization occurs There are four possible outcomes: GG (green leaves) Gg (green leaves) gg (yellow leaves) GG Gg Gg gg

Using Segregation to Predict Outcomes
What is the probability that the offspring will have yellow leaves? What is the probability that the offspring will have green leaves? gg GG, Gg, Gg

Punnett Squares A simple diagram used to predict the outcomes of a genetic cross How to make a Punnett Square: Write the genotypes of the parents Determine the alleles of all possible gametes that each parent could produce Draw a table with enough squares for each gamete of each parent Fill the table by combining the gametes’ genotypes Determine the genotype and phenotype of the offspring.

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