Genes, Heredity, & Gregor Mendel

Your unique combination of your characteristics are known as traits. Inherited traits: from your parents Acquired traits: developed during your life (ex: riding a bike, ability to read and write, interaction with the environment)

Genes Gene: a unit of heredity that occupies a specific location on a chromosome and codes for a particular trait. Heredity: the passing of genes from parents to offspring

Alleles Different form of the same gene 2 alleles for each gene, 1 on each chromosome Get 1 allele from each parent, because you get one set of chromosomes from each parent

Alleles So… Genes tell us the type of trait Hair color, eye color, etc. Alleles tell us the SPECIFIC trait Different forms of the same gene Blonde hair, blue eyes

DO NOW Homework out on your desk Notebooks open to continue notes on Heredity Answer this question: what is the difference between a GENE and an ALLELE?

Traits Phenotype Genotype The way an organism looks on the outside. Physical appearance Red hair, green eyes, etc. Genotype The combination of your genes Always listed as two letters, because two alleles Ex/ AA, Aa, aa

Genotype Homozygous Heterozygous Each allele is the same Ex/ each allele says brown eyes. Heterozygous Each allele is different Ex/ One allele says brown eyes, the other says blue eyes

Genotype: What Happens if I’m heterozygous? Some alleles are DOMINANT to others. Recessive allele: Represented by a LOWER CASE letter Must be homozygous recessive to display the phenotype of a recessive allele Dominant allele: Represented by an UPPER CASE letter Determines the phenotype Dominates the recessive allele in a heterozygous organism

Genetic first started when an Austrian monk, named Gregor Mendel, performed a series of experiments on garden peas. Mendel observed qualitative information about the traits of the pea plants. He then tried to quantify how those traits were passed from one generation to another. Mendel developed purebred lines of pea plants. He recorded the results of his experiments and made statistical notes about how the traits were passed down. The results of Mendel’s studies were so important that he is considered: Father of Genetics

WHY PEAS? Structure of the pea flowers Presence of distinctive traits Rapid reproduction cycle Grow quickly Produce large number of offspring Cheap and easy to grow and maintain Pea plants normally self-pollinate but can cross-pollinate if the anthers (the male parts) are removed when the flower is young

The Pea Plant Experiment Mendel studied characteristics in the parents and offspring of pea plants. The plants displayed several easily-observed characters in one of two contrasting traits or forms

The Pea Plant Experiment Studied and tracked one trait at a time over multiple generations.

Mendel observed that there were two different types of pea plants plants that, when self-pollinated, produce the same form of a trait in all offspring Example: white flower plants that produce offspring with white flowers Purebred Plants plants that, when self pollinated, produce more than one form of a trait in their offspring Example: Purple flower plants that produce some purple and some white flowered offspring Hybrid Plants

Mendel Concluded… Parent transmits information about traits to their offspring Gamete production and fertilization Each parent must contribute a form of a gene to the offspring Homozygous vs. heterozygous Symbols can be used to represent alleles Dominant vs. recessive Genetic make-up and observed characteristics are not always the same Genotype vs. phenotype

Law of Independent Assortment Law of Segregation As a result of his many years of careful study, Mendel’s work was summarized into three main laws. Law of Dominance Law of Independent Assortment Law of Segregation

Example: Green pod color is seen in plants with the genotype Gg Law of Dominance States that if two alleles in a gene pair are different, then one allele can control the trait and the other one can be hidden. Example: Green pod color is seen in plants with the genotype Gg

Law of Independent Assortment States that gene pairs segregate into gametes randomly and independently of each other. At what stage of meiosis does this occur? Metaphase I and Anaphase I of meiosis: homologous chromosomes randomly lineup and separate

Law of Segregation States that each pair of genes segregates, or separates, during meiosis and each gamete contains one gene from each gene pair. What is the chance that a gamete will end up with a maternal homolog at any one chromosome pair? ½ or 50% The chance that all 23 homologs from one parent will end up in a single gamete is 1 in 8 million (1/2)23

DO NOW: In your notebooks… Heterozygous or Homozygous? AA _______________ Bb _______________ ff _______________ Jj _______________ OO _______________ Ll _______________

Determine the Phenotype Purple flowers are dominant to white 1. PP ________________ 2. Pp ________________ 3. pp ________________

Determine the Phenotype Wrinkled seeds are recessive to round seeds 1. RR ________________ 2. Rr ________________ 3. rr ________________

Determine the Genotype Straight hair is dominant to curly hair 1. Straight _____________ 2. Straight _____________ 3. Curly _____________

Determine the Genotype Blue eyes are recessive to brown eyes 1. Brown _____________ 2. Brown _____________ 3. Blue _____________

Applying the Laws Knowing the genotype and phenotypes of the parents allows us to predict the POSSIBLE genotypes and phenotypes of the offspring… Use a Punnett Square P = Purple, dominant p = white, recessive

Applying the Laws: Punnett Squares Used to predict the outcome of genetic variation that results from sexual reproduction. Uses the genotypes of the parents to predict the genotypes (and thereby phenotypes) of the offspring Gives POSSIBLE outcomes IF the two parents were to mate

Punnett Squares Genotype of parent Individual Alleles are separated Represents the separating of chromosomes into gametes after meiosis Tt Tt tt tt Genotype of offspring

Punnett Square Practice Round seeds are dominant to wrinkled seeds A heterozygous parent is mated with a homozygous recessive parent. What percentage of the offspring will be round? ________ x ________