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The three areas of Genetics

1. Classical Genetics

2. Molecular Genetics

3. Evolutionary Genetics

Be sure you know the meaning/significance of the following already-familiar terms:

The Genome - the organism's basic complement of DNA
Most organisms have TWO COPIES of the genome, one from each parent, and are thus DIPLOID.
When one considers genes, it is most usually at the level of a single locus at a time. With respect to a single gene locus, be sure to recall the terms:

In eukaryotes, the genome is borne on a chromosomes, the number and conformation of which is species specific.

ONE SET OF CHROMOSOMES carries ONE COPY OF THE GENOME.
Hence, diploid organisms have TWO SETS OF CHROMOSOMES, each set carrying the same gene loci, though not necessarily the same alleles at each locus.

Two chromosomes (each from one of the two sets; one from mom, and one from dad) that have exactly the same array of gene loci are HOMOLOGOUS.

When a cell divides during MEIOSIS, the two homologs separate, and each daughter cell (destined to become a gamete) receives only one of each homologous pair.

Let's have a look at a picture to refresh our memory.

Recall The Central Dogma:

DNA is transcribed into RNA
RNA is translated into protein

  • Recall the difference between structural and enzymatic proteins

  • Recall the meaning of primary, secondary, tertiary and quaternary structure of proteins

    Obviously, much has been learned about how genetic information is transferred from generation to generation since Mendel's time. Methods of Study in Genetics (from coarse-grained to fine-grained):

    The genes are known to be located on a large, complex helix-shaped molecule known as DeoxyriboNucleic Acid - DNA.

    The information encoded on the DNA is in the form of an "alphabet" of nucleotide bases, Adenine, Guanine, Cytosine and Thymine.

    A diploid cell contains TWO COPIES of the organism's GENOME (entire complement of DNA); a haploid cell contains only one copy.

    The genome itself is assembled into a structure called a CHROMOSOME.

    And while we're on the subject, we are going to hear more about the words "primitive" and "derived". So let's define them now...

    Be sure you know and understand these terms!

    The Central Dogma: DNA is transcribed into RNA (RiboNucleic Acid) and translated into protein. (As we'll see later, the Central Dogma isn't all that hard and fast any more.)

    A protein is a chain of amino acids, and is also called a POLYPEPTIDE.

    Genetics touches every aspect of your life, and all of human existence. Control of genes is a major goal of many humans--for good or ill. The practice of applying genetic technology to commercial use is known as BIOTECHNOLOGY.

    Since humans became an agricultural species, we have sought to improve our domestic crops and livestock via selective breeding or ARTIFICIAL SELECTION. When a particularly desirable individual or strain is selected, the farmer may plant a crop that consists of these desirable individuals, and all are nearly genetically identical. This is a MONOCULTURE.

    While monocultures can be advantageous and productive, they also introduce pitfalls of which we must be aware:

    LOSS OF GENETIC DIVERSITY CAN LEAD TO RUIN.

    Humans seek to manipulate genes in an effort to improve quality of human life:

  • MOLECULAR GENETIC ENGINEERING - The manipulation of microbe DNA to produce bacteria which synthesize products useful to humans (such as insulin, hormones, etc.)
  • A TRANSGENIC cell is one which has permanently acquired foreign DNA that allows it to synthesize products it could not otherwise synthesize.
    Genetics are also put to use in crime-solving: DNA "fingerprinting" is the process of comparing DNA at a crime scene with that of a suspect. It can't positively identify a suspect, but it can give a statistical likelihood that a particular suspect shares the DNA of a crime scene.
    Genetics and medicine go hand in hand.
    With the data rolling in from the Human Genome Project (the participating labs have until the early years of this century to finish!), faulty genes can be identified that are responsible for heritable disorders such as muscular dystrophy, Huntington's disease, cystic fibrosis, etc.

    The study of DNA cannot be done without MODEL ORGANISMS: non-human species that can be used to study genes and gene expression in the hopes that they might be similar enough to human genes and gene expression to allow extrapolation. Such species include mice, fruit flies (Drosophila melanogaster, yeast and other easy-to-handle organisms that have relatively short generation times.

    In your text, review the meanings and significance of

    We now know that there are tremendous differences in the ways that prokaryotic and eukaryotic DNA is transcribed and translated. For example, eukaryotic cells have INTRONS--portion of transcribed DNA which are removed from the mRNA transcript before translation.
    Until relatively recently, most study was done on nuclear DNA. We now know that chloroplasts and mitochondria also have DNA, separate and different from the nucleus. Mitochondria are maternally inherited in almost all species. Plastid DNA's (mtDNA and cpDNA) can have a profound influence on an organism's phenotype and function.