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“Traits & Genes ”

“Traits & Genes ”. KEY CONCEPT Genes encode proteins that produce a diverse range of traits. 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.

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“Traits & Genes ”

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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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