Heredity and Genetics

I wonder… is square dominant over round for sponge shape???

HEREDITY The inheritance of traits from parents to offspring The inheritance of traits from parents to offspring

GENETICS the study of heredity

TRAIT A characteristic that distinguishes one individual from another.

Today’s Objectives Review about Gregor Mendel- the “father of genetics”Review about Gregor Mendel- the “father of genetics” Review dominant and recessive allelesReview dominant and recessive alleles Review genotype, phenotype, homozygous, heterozygousReview genotype, phenotype, homozygous, heterozygous Review Punnett SquaresReview Punnett Squares Practice heredity with Spongebob!Practice heredity with Spongebob!

Gregor Mendel Considered the “father of genetics”Considered the “father of genetics” An Austrian monk with a love of scienceAn Austrian monk with a love of science Experimented with garden peas- studying traits such as plant height, pea color, pea shape, flower colorExperimented with garden peas- studying traits such as plant height, pea color, pea shape, flower color Began his experiments in 1856Began his experiments in 1856 Experimented for 8 years on thousands of plantsExperimented for 8 years on thousands of plants His work was forgotten until other scientists confirmedHis work was forgotten until other scientists confirmed his findings in 1900 his findings in 1900

Alleles The different forms of a trait that a gene may haveThe different forms of a trait that a gene may have Examples in pea plants include: Short or tall plantShort or tall plant Red or white flowersRed or white flowers Green or yellow peasGreen or yellow peas

GENE is a part of a chromosome that determines a trait.GENE ALLELES are different forms of a gene.ALLELES CHROMOSOME ALLELE

Alleles Alleles can be DOMINANT: meaning they cover up (dominate) other alleles; or they can be recessive: meaning they can be covered up or seem to disappearAlleles can be DOMINANT: meaning they cover up (dominate) other alleles; or they can be recessive: meaning they can be covered up or seem to disappear The different alleles are shown by CAPITAL (DOMINANT) or lowercase (recessive) lettersThe different alleles are shown by CAPITAL (DOMINANT) or lowercase (recessive) letters

Alleles How do you determine which allele is dominant to begin with???How do you determine which allele is dominant to begin with??? For the recessive allele or form of a trait to be seen, the genotype MUST be a pure (homozygous) recessive (tt)For the recessive allele or form of a trait to be seen, the genotype MUST be a pure (homozygous) recessive (tt) The dominant form will show in either pure (homozygous) dominantOR heterozygous (mixed) (TT or Tt)The dominant form will show in either pure (homozygous) dominant OR heterozygous (mixed) (TT or Tt)

Alleles For example: If you cross two tall pea plants and get 75% tall and 25% short offspring you have to assume the cross (and genotypes) look like this…For example: If you cross two tall pea plants and get 75% tall and 25% short offspring you have to assume the cross (and genotypes) look like this… Punnett SquarePunnett Square TTTTTTTT TtTtTtTt TtTtTtTt tttttttt T t Tt

Alleles If the alleles are the same they are called homozygous. (also known as purebred)If the alleles are the same they are called homozygous. (also known as purebred) Example: TT or ttExample: TT or tt If the alleles are different they are called heterozygous. (also known as hybrid )If the alleles are different they are called heterozygous. (also known as hybrid ) Example: TtExample: Tt

Punnett Squares A simple chart for predicting the results of a crossA simple chart for predicting the results of a cross It shows the genotype: the genetic makeup of an organism (Tt)It shows the genotype: the genetic makeup of an organism (Tt) And the phenotype: the way the organism looks and behaves (photograph)And the phenotype: the way the organism looks and behaves (photograph)

Punnett Squares You cross a tall pea plant with a short pea plant. The offspring are 50% tall and 50% short…You cross a tall pea plant with a short pea plant. The offspring are 50% tall and 50% short… Tt tt T t tt

Today’s Challenge ! Spongebob Squarepants is square. He marries Spongesue Roundpants and they have four children. All four children are square.Spongebob Squarepants is square. He marries Spongesue Roundpants and they have four children. All four children are square. What is the genotype for these children?What is the genotype for these children? Show the Punnett square for this cross.Show the Punnett square for this cross. Which allele is dominant- square or round? How do you know?Which allele is dominant- square or round? How do you know? 5/16/2015