Genetics

• Allele


  Alternative form of a gene
• Autosome


  Chromosome that does not contain a sex determining gene
• Centromere


  Constricted area on the chromosome where the spindle attaches
• Chromatin


  DNA wrapped around proteins that is NOT condensed; uncondensed
• Chromosome


  A structure, consisting of DNA wrapped around histone proteins that carries genes
• Diploid


  Having two sets of chromosomes in the cell, or a species that contains two copies of each chromosome
• Expressed


  If a gene is copied and made into an mRNA and protein
• Gene


  A DNA sequence with a known function (encoding a protein or regulator)
• Genome


  The complete set of genetic instructions (DNA) characteristic of an organism = 3.2 billion base pairs
• Genotype


  The actual gene makeup of an individual for a trait, i.e. AA or Aa or aa
• Haploid


  Having only one set of the genome in the cell
• Homologous chromosomes (homologs)


  Have the same appearance and carry the same genes (one from mom and one, dad)
• Locus


  The spot on a chromosome where a gene resides
• mRNA


  A complimentary copy of a section of DNA (template strand), carries a codon used to make a protein
• Multifactorial


  A trait determined by one or more genes and the environment
• Mutation


  A change in the base sequence of a gene
• Phenotype


  The physical appearance or observable characteristic for a trait, i.e. freckles
• Polymorphism


  A variation in the DNA sequence that is present in at least 1 percent of the population
• Sister chromatids


  Two identical chromatids joined at the centromere
• SNP (Single Nucleotide polymorphism)


  A single base site that varies among individuals in a population, often related to diseases
• Telomeres


  Segments of DNA at the ends of chromosomes
• Somatic cell


  A body cell; is diploid; contains 2 sets of chromosomes
• Reproductive cells


  Gametes = sperm and egg; haploid- have only one set of chromosomes or only one chromosome of each homologous pairs
• Prokaryotic cells


  DNA is in nucleoid region, DNA is single, circular chromosome; cell wall surrounds plasma membrane
• Eukaryotic cells


  Had a nucleus, organelles, compartmentalization
• The Human Genome Project has identified approximately 22,000 genes that encode for proteins
• Mitosis


  Cell division with normal somatic cells and in development of embryo; one division; 2 daughter 2n cells
• Meiosis


  Cell division-produce reproductive cells (sperm and egg) reductional; two divisions, 4 daughter cells (n)
• Tetrad


  4 chromatids linked together in prophase – metaphase of Meiosis I
• Stages of cell division


  • Interphase (G1, G2, S)
  • Mitosis (Prophase, Prometaphase, Metaphase, Anaphase, Telophase)
  • Cytokinesis
• AABB


  Homozygous dominant for two traits
• Homozygous


  Condition when both alleles for a gene are the same
• Heterozygous


  Condition when the alleles for a gene are different
• Dominant


  An allele that is fully expressed if present
• Recessive


  An allele that is only expressed if there are no other alleles present
• Sex-linked


  Genes carried on the X and Y chromosomes
• Incomplete dominance


  Heterozygote produces a phenotype intermediate to homozygotes; 1:2:1 Phenotypic
• Codominance


  Both alleles are expressed in the heterozygote, so there is a 1:2:1 phenotypic ratio
• Epistasis


  One gene masks the effects of another gene (Labrador retriever) usually produces 9:3;4 ratio
• Pleiotropy


  One gene has several phenotypic effects