Introduction to Genetics Mr. Click 7 th Grade Life Science

Heredity is the passing of traits from parents to offspring. Heredity is the passing of traits from parents to offspring. Genetics is the study of heredity. Genetics is the study of heredity. Gregor Mendel is known as the “Father of Genetics.” Gregor Mendel is known as the “Father of Genetics.”

Who was Mendel? Mendel was a monk who lived in a monastery in Austria Mendel was a monk who lived in a monastery in Austria He spent a lot of time gardening and became interested in why plants looked the way that they did. He spent a lot of time gardening and became interested in why plants looked the way that they did. Mendel studied the characteristics of pea plants to see how traits were passed from parents to offspring. Mendel studied the characteristics of pea plants to see how traits were passed from parents to offspring.

Mendel’s Discovery Mendel noticed that some traits showed up more often than others. He called these traits: Mendel noticed that some traits showed up more often than others. He called these traits: - Dominant – they will cover up another trait that is present. - Recessive traits are the traits that get covered up. You only see recessive traits if you get one from each of your parents.

Genes are the sections of DNA that carry information about a certain trait. Genes are the sections of DNA that carry information about a certain trait. The different forms of a trait (whether it is dominant or recessive) are called alleles. The different forms of a trait (whether it is dominant or recessive) are called alleles. Dominant alleles are always shown with a capital letter. Dominant alleles are always shown with a capital letter. Recessive alleles are always shown with a lower case letter. Recessive alleles are always shown with a lower case letter.

Genes: a review Genes are the basic unit of heredity Genes are the basic unit of heredity Each chromosome contains many genes that code for different traits. Each chromosome contains many genes that code for different traits. Eye color Gene Eye color Gene Hair color Gene Hair color Gene

Alleles are represented with a genotype – a letter combination. Alleles are represented with a genotype – a letter combination. If the two letters in a genotype are the same, it is said to be homozygous Ex: HH, hh If the two letters in a genotype are the same, it is said to be homozygous Ex: HH, hh If the two letters are different (one capital, one lower case), it is said to be heterozygous. Ex. Hh If the two letters are different (one capital, one lower case), it is said to be heterozygous. Ex. Hh The phenotype is the physical appearance of a trait. The phenotype is the physical appearance of a trait.

Genes Genes are like committee members; all of the genes (the genotype) sit down together at a table and decide what the organism is going to look like (the phenotype) Genes are like committee members; all of the genes (the genotype) sit down together at a table and decide what the organism is going to look like (the phenotype)

Genotype Each gene has an opinion (an allele). Each gene has an opinion (an allele). When all of the genes are together at the table, they state what their opinion is (what allele they are). When all of the genes are together at the table, they state what their opinion is (what allele they are). Allele: Allele: Think of alleles as different Think of alleles as different flavors of genes flavors of genes

Genotype A a C b c B

Dominant Alleles Genes have different personalities Genes have different personalities Some genes are loud and bossy. They are always convinced that their ideas are the best, and they have to express them to everyone! Some genes are loud and bossy. They are always convinced that their ideas are the best, and they have to express them to everyone! We say that these genes are dominant alleles We say that these genes are dominant alleles Dominant alleles are written with capital letters. Dominant alleles are written with capital letters.

Recessive Alleles Some genes are very shy. They stare at their feet and just mumble something whenever they are asked a question. They might have some cool ideas, but they are afraid that they’ll be laughed at if they tell the dominant genes about them, so they keep quiet. Some genes are very shy. They stare at their feet and just mumble something whenever they are asked a question. They might have some cool ideas, but they are afraid that they’ll be laughed at if they tell the dominant genes about them, so they keep quiet. We say that these genes are recessive alleles We say that these genes are recessive alleles Recessive alleles are written with lower-case letters Recessive alleles are written with lower-case letters

Phenotype Phenotype- Any observable trait or characteristic of an organism Phenotype- Any observable trait or characteristic of an organism When the committee is deciding on what the animal will look like (phenotype), the genes split up into little sub-committees for each trait. When the committee is deciding on what the animal will look like (phenotype), the genes split up into little sub-committees for each trait. A subcommittee consists of only A subcommittee consists of only the copy of the gene from Mom and the copy of the gene from Dad.

Phenotype These two genes might discover that they are identical and they both agree that the exact same thing should be done. These two genes might discover that they are identical and they both agree that the exact same thing should be done. This means the two alleles are homozygous This means the two alleles are homozygous aa We will express a AA We will express A

Phenotype These two genes might discover that they are different alleles. Each gene has a different idea about how the trait should turn out. These two genes might discover that they are different alleles. Each gene has a different idea about how the trait should turn out. This means the two alleles are heterozygous This means the two alleles are heterozygous In this case: In this case: When the decisions are made When the decisions are made about what the animal will look like, you see only the dominant gene's ideas. A a We will express A

Practice: Assume the following: Assume the following: C: Straight hair C: Straight hair c: Curly hair c: Curly hair A person who has curly hair has what genotype? A person who has curly hair has what genotype? A person who has a genotype of Cc has what phenotype? A person who has a genotype of Cc has what phenotype?

Practice For each genotype below, indicate whether it is heterozygous (He) or homozygous (Ho) For each genotype below, indicate whether it is heterozygous (He) or homozygous (Ho) AA _____ Ee ____ Ii _____ Mm _____ Bb _____ ff ____ Jj _____ nn _____ Cc _____ Gg ____ kk _____ oo _____ DD _____ HH ____ LL _____ Pp _____

Practice For each of the genotypes below determine what phenotypes would be possible. For each of the genotypes below determine what phenotypes would be possible. Purple flowers are dominant to white flowers. Purple flowers are dominant to white flowers. PP___________________ PP___________________ Pp___________________ Pp___________________ pp___________________ pp___________________

Bobtails in cats are recessive. Bobtails in cats are recessive. TT _________________ TT _________________ Tt _________________ Tt _________________ tt________________ tt________________ Brown eyes are dominant to blue eyes Brown eyes are dominant to blue eyes BB_________________ BB_________________ Bb________________ Bb________________ bb________________ bb________________

For each phenotype below, list the genotypes (remember to use the letter of the dominant trait) For each phenotype below, list the genotypes (remember to use the letter of the dominant trait) Straight hair is dominant to curly. Straight hair is dominant to curly. _____ straight _____ straight _____ curly _____ curly Pointed heads are dominant to round heads. Pointed heads are dominant to round heads. _____ pointed _____ pointed _____ round _____ round

Helpful Video from Khan Academy For help with Punnett Squares go to: For help with Punnett Squares go to: mcxM mcxM

Punnett Squares Set up the Punnet squares for each of the crosses listed below. Set up the Punnet squares for each of the crosses listed below. Normal height plants are dominant to dwarf plants. Normal height plants are dominant to dwarf plants. RR x rr RR x rr What percentage of the offspring will be normal height?_________________ What percentage of the offspring will be normal height?_________________

Punnett Squares Set up the Punnet squares for each of the crosses listed below. Set up the Punnet squares for each of the crosses listed below. Normal height plants are dominant to dwarf plants. Normal height plants are dominant to dwarf plants. Rr x Rr Rr x Rr What percentage of the offspring will be normal height?_________________ What percentage of the offspring will be normal height?_________________

Punnett Squares Set up the Punnet squares for each of the crosses listed below. Set up the Punnet squares for each of the crosses listed below. Normal height plants are dominant to dwarf plants. Normal height plants are dominant to dwarf plants. Rr x rr Rr x rr What percentage of the offspring will be normal height?_________________ What percentage of the offspring will be normal height?_________________

Punnett Squares Set up the Punnet squares for each of the crosses listed below. Set up the Punnet squares for each of the crosses listed below. Normal height plants are dominant to dwarf plants. Normal height plants are dominant to dwarf plants. RR x Rr RR x Rr What percentage of the offspring will be normal height?_________________ What percentage of the offspring will be normal height?_________________

A TT (tall) plant is crossed with a tt (short plant). A TT (tall) plant is crossed with a tt (short plant). What percentage of the offspring will be tall? ___________ What percentage of the offspring will be tall? ___________ A Tt plant is crossed with a Tt plant. A Tt plant is crossed with a Tt plant. What percentage of the offspring will be short? ______ What percentage of the offspring will be short? ______ A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR). A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR). What percentage of the offspring will be homozygous (RR)? __________ What percentage of the offspring will be homozygous (RR)? __________

Note 44) Mendel’s Laws of Genetics Mendel’s Law of Segregation states that because of meiosis, each gamete that is made only only receives 1 copy of each gene. Mendel’s Law of Segregation states that because of meiosis, each gamete that is made only only receives 1 copy of each gene. Mendel’s Law of Independent Assortment states that the alleles of different genes sort independently of each other during meiosis. In other words, inheriting one trait cannot influence another trait. Mendel’s Law of Independent Assortment states that the alleles of different genes sort independently of each other during meiosis. In other words, inheriting one trait cannot influence another trait.

Mendel’s Law of Dominance states that if you have a heterozygous organism, you will only see the dominant trait and the recessive will be hidden. Mendel’s Law of Dominance states that if you have a heterozygous organism, you will only see the dominant trait and the recessive will be hidden.