New Core Curriculum Classical Genetics Foundations of Scientific Process

1) DNA encodes RNA 2) RNA encodes Proteins 3) Proteins encode shape/function  Genetic information (the MEANING) is encoded in the SEQUENCE of basis along the DNA strand;  DNA is not a direct template for protein synthesis; The Central Dogma of Molecular Biology: DNA  RNA  Protein

The History of Classical Genetics NATURE|Vol 441|25 May 2006

Establishing Basic Terminology and Definitions: Gene = is a stretch of DNA that contains the instructions for making a protein; Allele = alternative forms of genes for a certain characteristics (ex. alleles for flower color or earlobe shape); Homozygous (EE, ee) & Heteorzygous (Ee); Genotype = genetic makeup of an organism; Phenotype = observed characteristics of organism; The phenotype is produced by the interaction of genes and the environment.

It has been long known that offspring resemble parents. Animals and plants selectively bred for many centuries. Gregor Mendel was the first to explain the principles of heredity in the mid-nineteenth century. He investigated heredity in pea plants Garden pea grow easily, produce large numbers of seeds quickly, and self-fertilize. Pea Plants have distinctive characters: Purple OR White flowers

Mendel isolated true-breeding strains Traits were selected because they had two distinct phenotypes Scientific Process of discovery….establishing Classical Genetics

Mendel crossbred plants with different alleles Gamete is a cell that is involved in sexual reproduction. A male and female gamete unite to produce a zygote that will develop into offspring.

Interpretation of Mendel’s Results  Laws of Heredity: Law of dominance: When an organism has 2 alleles for a given trait, the allele that is expressed (overshadows the expression of the other allele) is the dominant allele. The overshadowed allele is called recessive allele. notation convention: Y - dominant allele (ex. purple) y - recessive allele (ex. white) YY - homozygous dominant Yy - heterozygous yy - homozygous recessive

Deleterious recessive alleles persist in the population because heterozygous individuals carry the allele without developing the phenotype, and are not at a selective disadvantage. If both parents are homozygous for the recessive trait, all their progeny will usually also have the trait. Recessive traits are usually the result of a mutation causing loss or modification of gene product. ex. Albinism: characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin You could construct a family tree of either your family or friend’s family by using character for ear lobe type (recessive vs. dominant) non-attached is dominant

Interpretation of Mendel’s Results  Laws of Heredity: Law of dominance: When an organism has 2 alleles for a given trait, the allele that is expressed (overshadows the expression of the other allele) is the dominant allele. The overshadowed allele is called recessive allele. Law of segregation: Parental alleles of a gene separate in process called meiosis into gametes (reproductive cells). In the process of gametes formation, the alleles that control a trait separate form one another retaining their individuality. Law of independent assortment: If two different genes are found on separate chromosomes, where the one allele goes is not influenced by where the other goes.

parental alleles of a gene separate in process called meiosis into gametes semi-conservative replication of DNA

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