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Genes and Traits in Genetics

Explore how genes encode proteins to produce various traits, including alleles, genotypes, and phenotypes. Learn about Mendel's observed traits, dominance rules, and genetic influences on development phenomena.

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Genes and Traits in Genetics

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  1. “Traits & Genes”

  2. KEY CONCEPT Genes encode proteins that produce a diverse range of traits

  3. A gene is a piece of DNA that tells a cell to make a certain protein. • Each gene has a locus, a specific position on a pair of homologous chromosomes

  4. An allele is an alternative form of a gene • -Each parent donates one allele for every gene • For shape, there is a wrinkled allele and a round allele. They receive one allele from each parent.

  5. Genotype • Homozygous (pure) • when both letters are the same • ex: TT, tt • Heterozygous (hybrid) • when letters are different • always write the big letter first • ex: Tt , Xx , Bb • Dominant Alleles are always upper case and recessive alleles are always lower case.

  6. E. Mendel’s observed traits • Rule of Dominance: When a dominant trait is present the recessive trait is hidden

  7. Genes influence the development of traits. • All of an organism’s genetic material is called the genome. • A genotype refers to the actual genes. • A phenotype is the physical expression of a trait.

  8. C. Genotype: 1. The gene combination of an organism • It consists of 2 alleles • For example: • PP • Pp • pp

  9. Phenotype :The appearance. • The genotype determines the phenotype.

  10. Probability: The likelihood of an event. • A probability is expressed as a percentage or a fraction. • Genotypic Ratio: The ratio of genotypes that will appear. • Phenotypic Ratio: The ratio of phenotypes that will appear. • We can find the probability of a certain genotype or phenotype by constructing a Punnett Square.

  11. When a dominant allele always gets its way (the dominant phenotype is present no matter its partner) it is called COMPLETE DOMINANCE. • Example: • Pp = Purple Flower • PP = Purple Flower • Some times dominant traits don’t completely get their way……the alleles compromise. This results in a phenotype that is a mix of both parents. This is called INCOMPLETE DOMINANCE. • Example • Pp = light purple flower

  12. In a few instances both alleles need to be expressed. This is called Codominance. • Example • A mom chicken is black and dad chicken is white, but the baby chick comes out black and white.

  13. Most traits occur in a range and do not follow simple dominant-recessive patterns

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