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Mendelian genetics Unit 5 LT 8.10.1. Intro to genetics. Traits. Hook - Before we begin…. ..think about this…

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Mendelian genetics Unit 5 LT 8.10.1

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Mendelian geneticsUnit 5LT 8.10.1

Intro to genetics




Hook - Before we begin…

..think about this…

  • What are some traits you have that make you look like your mom or dad? If you don’t know what your mom or dad looks like, what are some qualities that make you look unique from the rest of your family? Or do you look more like one parent than another?

  • Why do you think this is???

JTPS - What color will be…

.. The puppy of these two dogs?

J-TPS (Justify –Think Pair Share)





  • What genetic principles account for the transmission of traits from parents to offspring?

  • One possible explanation of heredity is a “blending” hypothesis - The idea that genetic material contributed by two parents mixes in a manner analogous to the way blue and yellow paints blend to make green

  • An alternative to the blending model is the “particulate” hypothesis of inheritance: the gene idea - Parents pass on discrete heritable units, genes


  • Austrian Monk that did research in the field of genetics during the mid 19th century

  • Genetics is the study of biological inheritance patterns and variation

  • Between 1856 and 1863 Mendel grew and tested over 28,000 pea plants

Mendel studied peas for 8 years. Why peas?

Mendel’s Peas

  • Easy to grow

  • Easily identifiable traits

  • Can work with large numbers of samples

Mendel’s research showed that genes are inherited as units called alleles.

  • Genes may be the same but the alleles (or units) may be different.

Genes for eye color

Dominant and recessive


  • Mendel crossed (mated) two pure breed parents (Parental “P” generation) to produce the (First offspring “F1” generation)


Pure breed Purple flower


Pure breed white flower


What did he obtain?

  • Mendel noticed that all of the F1 generation had purple flowers

  • He concluded that the dominant allele was expressed

  • What disappeared in the 1st generation?

  • What reappeared in the 2nd generation?

  • Mendel allowed the F1 generation cross pollinate (mate with each other.)

  • The F2 generation showed some purple and some with white flowers.

Ratio of


  • What disappeared in the 1st generation?

  • The trait for white

  • What reappeared in the 2nd generation?

  • The trait for white



  • Traits (visible characteristics) are inherited as discrete (separate and unconnected) units called alleles

Male gamete


Female gamete


Homozygous alleles

  • Both chromosomes and alleles are the same

Heterozygous Alleles

  • Both chromosomes are the same, but the alleles are different

Law of Segregation:

  • Organisms inherit two copies of each gene, one from each parent (the two alleles segregate/separate during gamete formation).

  • Parents donate only one copy of each gene in their gametes

Law of Segregation











  • Character: a heritable feature, such as flower color

  • Trait: a variant of a character, such as purple or white flowers

  • Each trait carries two copies of a unit of inheritance, one inherited from the mother and the other from the father

  • Alternative forms of traits are called alleles

Phenotype vs Genotype

Genetics song

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