ATR 250
Chapter 3: Genetics- Reproducing life and Producing Variation

amino acids    Organic molecules combined in a specific sequence to form a protein.
antibodies    Molecules that form as part of the primary immune response to the presence of foreign substances; they attach to the foreign antigens.
antigens    Substances, such as bacteria, foreign blood cells, and enzymes, that stimulate the immune system's antibody production.
autosomes   All chromosomes, except the sex chromosomes, that occur in pairs in all somatic cells (not the gametes).
coding DNA    Sequences of a gene's DNA (also known as exons) that are coded to produce a specific protein and are transcribed and translated during protein synthesis.
 codominance   Refers to two different alleles that are equally dominant; both are fully expressed in a heterozygote's phenotype.
 codons    The sequences of three nitrogen bases carried by mRNA that are coded to produce specific amino acids in protein synthesis.
complementary bases    The predictable pairing of nitrogen bases in the structure of DNA and RNA, such that adenine and thymine always pair together (adenine and uracil in RNA) and cytosine and guanine
pair together.
cross-over    The process by which homologous chromosomes partially wrap around each other and exchange 
genetic information during meiosis.
cytoplasm    The jellylike substance inside the cell membrane that surrounds the nucleus and in which the organelles are suspended.
eukaryotes   Multicelled organisms that have a membrane-bound nucleus containing both the genetic material and specialized organelles.
gametes    Sexual reproductive cells, ova and sperm, that have a haploid number of chromosomes and that can unite with a gamete of the opposite sex to form a new organism.
genome   The complete set of chromosomes for an organism or species that represents all the inheritable traits.
heterozygous    Refers to the condition in which a pair of alleles at a single locus on homologous chromosomes are different.
homeotic (Hox) genes Also known as homeobox genes, they are responsible for differentiating the specific segments of the body, such as the head, tail, and limbs, during embryological development.
homologous    Refers to each set of paired chromosomes in the genome.
homozygous    Refers to the condition in which a pair of alleles at a single locus on homologous chromosomes are the same.
karyotype    The characteristics of the chromosomes for an individual organism or a species, such as number, size, and type.
linkage    Refers to the inheritance, as a unit, of individual genes closely located on a chromosome; an exception to the Law of Independent Assortment.
locus    The location of an allele, or gene, on a chromosome.
meiosis    The production of gametes through one DNA replication and two cell (and nuclear) divisions, creating four haploid gametic cells.
mitochondria    Energy-producing (ATP) organelles in eukaryotic cells; they possess their own independent DNA.
mitosis    The process of cellular and nuclear division that creates two identical diploid daughter cells.
nondisjuncdons Refers to the failure of the chromosomes to properly segregate during meiosis, creating some gametes with abnormal numbers of chromosomes.
nucleotide   The building block of DNA and RNA, comprised of a sugar, a phosphate group, and one of four nitrogen bases.
nucleus A membrane-bound structure in eukaryotic cells that contains  the genetic material.
peptide bond Chemical bond that joins amino acids into a protein chain.
pleiotropy    Refers to one gene that affects more than one phenotypic trait.
polygenic    Refers to one phenotypic trait that is affected by two or more genes.
polymorphism    Refers to the presence of two or more separate pheno-types for a certain gene in the population.
polypeptide   Also known as a protein, a chain of amino acids held together by multiple peptide bonds.
prokaryotes    Single-celled organisms with no  nuclear membranes  or organelles and with their genetic material as a single strand in the cytoplasm.
recombination    The exchange of genetic material between homologous chromosomes, resulting from a cross-over event.
regulatory genes    Genes that determine when other genes are turned on and off for protein synthesis.
replication    The process of copying nuclear DNA prior to cell division, so that each new daughter cell receives a complete complement of DNA.
 ribonucleic acid (RNA)    A single-stranded molecule involved in protein synthesis, consisting of a phosphate, ribose sugar, and one of four nitrogen bases.
ribosomes   The organelles attached to the surface of endoplasmic reticulum, located in the cytoplasm of a cell; they are the site of protein synthesis.
sex chromosomes The pair of chromosomes that determine an organism's biological sex.
single nucleotide polymorphisms (SNPs) Variations in the DNA sequence due to the change of a single nitrogen base; also known as point mutations.
somatic cells  Diploid cells that form the organs, tissues, and other parts of an organism's body.
structural genes Genes coded to produce particular products, such as an enzyme or hormone, rather than for regulatory proteins.
transcription    The first step of protein synthesis, involving the creation of mRNA based on the DNA template.
translation    The second step of protein synthesis, involving the transfer of amino acids by tRNA to the ribosomes, which are then added to the protein chain.
triplets    Sequences of three nitrogen bases each in DNA, known as codons in mRNA.
trisomy    Refers to the condition in which an additional chromosome exists with the homologous pair.
zygote    The cell that results from a sperm's fertilization of an ovum.