Bellringer 11/5/13 What is the relationship between DNA and the way you look? What is the relationship between DNA and the way you look?

Topic: Introduction into genetics EQ: What is genetics?

The nucleus of a cell contains genetic material The nucleus of a cell contains genetic material DNA  chromosomes  genes -> Alleles Genetic Material

Who was Gregor Mendel and what is genetics? Gregor Mendel was an Austrian monk in the mid-nineteenth century. Gregor Mendel was an Austrian monk in the mid-nineteenth century. He carried out the first important studies of heredity by using pea plants. He carried out the first important studies of heredity by using pea plants. Genetics is the branch of biology that studies heredity. Genetics is the branch of biology that studies heredity.

Inheritance Occurs when traits are passed down from parent to child. Occurs when traits are passed down from parent to child.

Traits The different versions of a characteristic The different versions of a characteristic Example: blue, green, and brown eyes Example: blue, green, and brown eyes

What is heredity? Heredity is the passing on of characteristics from parents to offspring. Heredity is the passing on of characteristics from parents to offspring. The characteristics that are passed down are called traits. The characteristics that are passed down are called traits.

Gregor Mendel’s Monohybrid Cross (p.156 in science book) 1 st Generation= Tall Peas X short Peas 2 nd Generation= All tall Peas 3 rd Generation= ¾ produced tall peas (75%), ¼ produced short peas (25%) A monohybrid cross is when you cross two plants that differ only by one trait.

The Rule of Unit Factors After seeing what happened Mendel concluded that there are two factors that control each trait. After seeing what happened Mendel concluded that there are two factors that control each trait. We now know that these factors are called genes. We now know that these factors are called genes. Each gene has different forms that are called alleles. One allele is inherited from each of the parents. Each gene has different forms that are called alleles. One allele is inherited from each of the parents.

Genes and Alleles Each chromosome has information about thousands of traits Each chromosome has information about thousands of traits Gene- section on chromosome that has information for one trait Gene- section on chromosome that has information for one trait See page 174

Genes Genes are short sections of chromosomes Genes are short sections of chromosomes

What are Genes? Factors that are passed from one generation to the next… Genes come in different forms called alleles: ex: tall and short Some are seen and some are not

Genes come in pairs Since chromosomes come in pairs (one from mom, one from dad) Since chromosomes come in pairs (one from mom, one from dad) Genes come in pairs Genes come in pairs karyotype_male.gif

The Rule of Dominance When the offspring inherit two different alleles for one trait, the trait that is expressed is said to be dominant while the other is recessive. When the offspring inherit two different alleles for one trait, the trait that is expressed is said to be dominant while the other is recessive. In Mendel’s pea plants that had one allele for tall and one allele for short, the peas were tall because tall is the dominant trait. In Mendel’s pea plants that had one allele for tall and one allele for short, the peas were tall because tall is the dominant trait. Recessive Dominant

Genes Dominant: those traits that are seen Dominant: those traits that are seen Recessive: those traits that are not seen Recessive: those traits that are not seen Thus came the principle of dominance: some are dominant and others are recessive Thus came the principle of dominance: some are dominant and others are recessive Recessive allele

Talk about dominant genes!!! Martin Sheen Charlie Sheen Emilio Estevez Kirk Douglas Michael Kirk

Activity Cut out figure 3 pg. 166 Cut out figure 3 pg. 166 Answer the Visual Check #7. Be sure to use the terms dominant and recessive in your answer. Answer the Visual Check #7. Be sure to use the terms dominant and recessive in your answer.

Genotypes and Phenotypes A Genotype is a specific combination of alleles. A Phenotype is the visual trait that is expressed. Possible Generation= TT Tt Tt tt Possible Genotypes= TT Tt Tt tt Possible Phenotypes= Tall, Tall, Tall, short Tall Allele short Allele

Homozygous and Heterozygous An organism is homozygous dominant for a trait if both of the alleles carry the dominant gene. An organism is homozygous dominant for a trait if both of the alleles carry the dominant gene. An organism is said to be homozygous recessive for a trait if the alleles both carry the recessive gene. An organism is said to be homozygous recessive for a trait if the alleles both carry the recessive gene. An organism is heterozygous for a trait if the two alleles are different. An organism is heterozygous for a trait if the two alleles are different. rr = Homozygous recessive (pure) RR = Homozygous dominant (pure) Rr = Heterozygous (Hybrid)

1 st Generation= Tt X Tt TTTt Tttt T t T t 2 nd Generation= TT, Tt, Tt, tt Genotype Ratio = 25% homozygous tall, 50% heterozygous tall, 25% homozygous short Phenotype Ratio = 3 Tall, 1 short

Using Alleles in Mendel’s Experiment Using Alleles in Mendel’s Experiment TtTt TtTt P1 Generation= TT X tt Punnett Square – a tool used to visualize all the possible combinations of alleles from the parents t T T Tall Allele Short Allele Genotype Ratio = 100% Tt (heterozygous Tall) Phenotype Ratio = 100% Tall 0% short

Pea Plant Traits