Traits/Variations/Mendel Unit 4 Part 2

How do we look the way we do? Proteins control our traits What is a trait? a specific characteristic, for example, eye color or height that varies from one individual to another. The differences among these traits are called variations? the differences that an organism can inherit for a trait

Who discovered all this? Gregor Mendel Father of Genetics First person to describe how traits are passed on from each generation. Austrian monk in the early1800’s Discovered the principles of genetics Studied 7 characteristics of pea plants

Why peas? Mendel studied peas for several reasons They have distinct male and female parts There are 7 basic characteristics of pea plants They can self-pollinate and cross-pollinate.

Terms to Know: Cross combining gametes from parents with different traits Self-Pollinate pollination that occurs from the joining of pollen and ovary of the same flower Cross-Pollination pollination that occurs from the joining of pollen and ovary of different flowers Allele different forms of the same gene, the genes you inherit from your parents. Gene located on chromosomes, they control how an organism develops Fertilization the uniting of male and female gametes

Green pea pods x green pea pods Mendel’s experiment Cross pollinated Green pea pods x green pea pods = All green pods Self pollinated Green pods x green pods = ¾ green pods ¼ yellow pods Mendel took two pea plants and crossed them. What did he find? He discovered different laws and rules that explain factors affecting heredity.

Mendel’s Laws/Rules Law of Dominance Law of Segregation The trait that is observed in the offspring is the dominant trait (Use uppercase letters to describe) The trait that disappears in the offspring is the recessive trait (use lowercase letters to describe) The two alleles for a trait must separate when gametes are formed A parent randomly passes only one allele for each trait to each offspring

More Terms to Know Dominant The trait that is observed or expressed Use a capital letter (T) Recessive The trait that is covered up or not expressed Use a lowercase letter (t) Heterozygous If the alleles for the inherited trait are different; one dominant and one recessive Use a capital & lowercase letter (Tt) Homozygous If the alleles for the inherited trait are the same; both dominant or both recessive Use two capital letters or two lowercase letters (TT, tt) Genotype The gene combination of an organism TT, Tt, tt Phenotype The way that an organism looks Tall/short

Dominant vs. Recessive

Genotypes vs. Phenotypes HH or Hh (black hair) hh (brown hair) Phenotypes Black (black hair) Brown (brown hair)