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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 divisions 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
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
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
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)
