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Chapter 2 Genetics Outline and Review

Chapter 2 Genetics Outline and Review - Chapter 2 Genetics...

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Chapter 2: Genetics 1. Mendel’s Genetics Experiments 1. Pea plants o From 1856 to 1863, Mendel conducted a series of experiments with the common pea. o He chose two variants to study: color and texture. 2. Experiment results o An organism’s phenotype (observed characteristics) is determined jointly by particles inherited from the mother and the father. o Each particle is equally likely to be passed on to the next generation (independent assortment). o Mendel published his results in 1866, but they were dismissed by leading botanists of the time. o By the end of the nineteenth century, other botanists were repeating Mendel’s experiments with other plant species. 2. Cells and Chromosomes 1. Mitosis and meiosis o The division of cells and their nuclei is called mitosis. o During mitosis, chromosomes can be seen. o Diploid organisms, like primates, have chromosomes in homologous pairs. o Meiosis is the cell division that produces gametes, or the eggs and sperm. o Haploid cells, like sex cells, contain only one copy of each chromosome. o Reproduction joins a haploid sperm and a haploid egg to create a diploid zygote. 2. Genes o Genes are particles carried on chromosomes. Collectively, all of the genes on a chromosome are known as the genome. o Alleles are variants of genes. o Individuals with two of the same allele are homozygous, while individuals with two different alleles are heterozygous. o The set of genes that an individual carries is the genotype, while the outward expression of those genes is the phenotype. o When only one copy of an allele is necessary to create a change in an organism’s phenotype, the allele is called dominant. If two copies are needed, it is said to be recessive. o A Punnet square can be constructed to predict the genotypes of offspring (Figure 2.10).
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Chapter 2: Genetics 3. Linkage and recombination o New traits are produced during “shuffling” of the genetic code, a process called recombination. o Crossing over creates chromosomes in an offspring that have gene combinations not present in the parent. 3. Molecular Genetics 1. How DNA works o Watson and Crick discovered the structure of DNA in 1953. o DNA is composed of sequences of phosphate and sugar molecules with one of four bases attached: adenine, guanine, cytosine, thymine. o Copying of DNA is accomplished by unzipping the double-helix strands, adding complementary bases, and proofreading the result. 2. DNA encoding o Protein-coding genes specify the structure of proteins such as enzymes, which regulate the biomechanics of an organism. o Regulatory genes determine when the message in the DNA will be expressed. o Some DNA codes for RNA molecules. 3. Protein encoding o Examples of proteins include keratin (hair) and collagen (bone). o Proteins are composed of strings of amino acids.
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