3. Heredity and Evolution
Genetics - The study of gene structure and action and the pattern of transmission of traits from parent to offspring
Nucleus - A organelle found in all eukaryotic cells - contains chromosomes (nuclear DNA)
Deoxyribonucleic acid (DNA) - The double-stranded molecule that contains the genetic code - main component of chromosomes
Ribonucleic acid (RNA) - A molecule similar in structure to DNA - three different single-stranded forms of RNA are essential to protein synthesis
Cytoplasm - Consists of a semi-fluid material and contains numerous structures involved in cell function
Cells - the basic units of life in all living things
Multicellular forms - plants, insects, birds, and mammals - composed of billions of cells
Prokaryotes - single-celled organisms ex. bacteria
Eukaryotic cells - structurally more complex cells that are found in multicellular organisms
Proteins - Three-dimensional molecules that serve a wide variety of functions through their ability to bind to other molecules
Protein synthesis - The assembly of chains of amino acids into functional protein molecules - the process is directed by DNA
Two types of cells - somatic cells and gametes
Somatic cells - cellular components of body tissues, such as muscle, bone, skin, nerves, heart, and brain
Gametes - Reproductive cells (eggs and sperm in animals) developed from precursor cells in ovaries and testes
Zygote - A cell formed by the union of an egg and a sperm cell - contains the full complement 46 chromosomes - can turn into an organism
Molecule - A structure made up of two or more atoms - can combine with others to make up more complex structures
Nucleotides - Basic units of the DNA molecule, composed of a sugar, a phosphate unit and one of four DNA bases
Enzymes - Specialized proteins that initiate and direct chemical reactions in the body
Complementary - Referring to the fact that DNA bases form base pairs in a precise manner. Ex, adenine - thymine
Hemoglobin - A protein molecule that occurs in red blood cells and binds to oxygen molecules
Hormones - Substances (usually proteins) that are produced by specialized cells and travel to other parts of the body, where they influence chemical reactions and regulate various cellular functions
Proteins are made up of chains of smaller molecules - amino acids
Amino Acids - 20 different acids which make up proteins
Gene - A sequence of DNA bases that specifies the order of amino acids in an entire protein, a portion of a protein, or any functional product
Mutation - A change in DNA - bases or chromosome numbers
Regulatory genes - Genes that code for the production of proteins that can influence the action of other genes - active only during certain stages of development
Homeobox (Hox) genes - An evolutionarily ancient family of regulatory genes. They direct the segmentation and patterning of the overall body plan during embryonic development
Chromosomes - Structures, composed of DNA and protein, found only in the nuclei of cells
Centromere - The constricted portion of a chromosome - after replication, the two strands of a double-stranded chromosome are joined at the centromere
Autosomes - All chromosomes except the sex chromosomes
Sex chromosomes - The X and Y chromosomes - The Y chromosome determines if it’s a male or not
Mitosis - Simple cell division -the process by which somatic cells divide to produce two identical daughter cells
Meiosis - Cell division in specialized cells in ovaries and testes - meiosis involves two divi- sions and results in four daughter cells, each containing only half the original number of chromosomes
Recombination - The exchange of DNA between paired chromosomes during meiosis - also called crossing over
Clones - A clone is an organism that is genetically identical to another organism - the term may also be used to refer to genetically identical DNA segments and molecules
Principle of segregation - Genes (alleles) occur in pairs because chromosomes occur in pairs - Ex. During gamete production, the members of each gene pair separate
Recessive - Describing a trait that is not expressed in heterozygotes; also refers to the allele that governs the trait (homozygous)
Dominant - Describing a trait governed by an allele that can be expressed in the presence of another, different allele (heterozygous)
Locus (.pl., loci) - The position on a chromosome where a given gene occurs
Alleles - Alternate forms of a gene
Homozygous - Having the same allele at the same locus on both members of a chromosome pair
Heterozygous - Having different alleles at a particular locus on the members of a chromosome pair
Genotype - The genetic makeup of an individual
Phenotypes - The observable or detectable physical characteristics of an organism
Principle of independent assortment - The distribution of one pair of alleles into gametes does not influence the distribution of another pair - The genes controlling different traits are inherited independently of one another
Mendelian traits - Characteristics that are influenced by alleles at only one genetic locus - Ex. blood types, genetic disorders - sickle-cell anemia etc
Antigens - Large molecules found on the surface of cells - toxic foreign substances that attack blood cells
Codominance - The expression of both alleles in heterozygotes - neither allele is dominant or recessive - both influence the phenotype
Human Genome Project - An international effort that has mapped the entire human genome
Variation - Inherited differences among individuals - the basis of all evolutionary change
Evolution - A change in the frequency of alleles from one generation to the next
Allele frequency - In a population, the percentage of all the alleles at a locus accounted for by one specific allele
Population - Within a species - a community of individuals where mates are usually found
Microevolution - Small changes occurring within species -a change in allele frequencies
Macroevolution - Changes produced only after many generations - such as the appearance of a new species
Gene flow - Exchange of genes between populations
Gene pool - The total complement of genes shared by the reproductive members of a population
Genetic drift - Evolutionary changes - changes in allele frequencies-produced by random factors - result of population size
Founder effect - A type of genetic drift in which allele frequencies are altered in small populations that are taken from, or are remnants of, larger populations
Directional change - The nonrandom change in allele frequencies caused by natural selection - change is directional - frequencies of alleles consistently increase or decrease (they change in one direction)