Chapter 3: Genetics and Heredity, Principles of Hereditary Transmission

Chapter 3: Genetics and Heredity, Principles of Hereditary Transmission

1. Genotype: Total endowment inherited by an individual

   • Phenotype: Set of traits a person actually displays, resulting from a combination of the person’s genotype (potential) and life experiences that modify that potentia
   • A person's characteristics are created by their genotype and their individual experiences

2. Gregor Mendel

   • Hereditary characteristics are determined by pairs of particles called factors
     • Factors later was termed genes
       • Genes: the specialized sequences of molecules that form the genotype
         • Genes are made up of nucleotides
           • Nucleotides: Repeating basic building block of DNA consisting of nitrogen-based molecules of adenine, thymine, cytosine, and guanine
             • The nucleotides pair together to create DNA
               • DNA, deoxyribonucleic acid: Blueprint for genetic inheritance
       • Information provided by genes are not always the same
         • Alleles: Alternate form of a specific gene, provides a genetic basis for many individual differences
   • Genes are transmitted from parents to children by gametes or sex cells
     • Gametes: Sperm cell in males, egg cell in females
   • Chromosomes were discovered around the same time Mendel research was published
     • Chromosomes: Threadlike structure of DNA, located in the nucleus of cells, which forms a collection of genes
       • A karyotype: the pictorial representation of an individual's chromosomes
         • Looking at a karyotype one can see the autosomes and the X & Y chromosomes (sex cells)
           • Autosomes: One of twenty-two pairs of homologous chromosomes
           • X chromosomes: Larger of the two chromosomes, normally females have two and males only one
           • Y chromosomes: Smaller of the two chromosomes, males have one and females have none
     • Watson and Crick proposed the way genes duplicate and documented the 46 chromosomes in the human body which led to the mapping of human genome
       • Human genome: Entire inventory of nucleotide base pairs that compose the genes and chromosomes of humans

3. Cell division and Chromosome Duplication

   • We were created by the uniting of the sperm cell (23 chromosomes) and the egg (23 chromosomes) to create the zygote
     • Zygote: fertilized egg cell
     • From then on the cells begin to divide through mitosis and meiosis
       • Mitosis: Process of cell division that takes place in most cells of the human body and results in a full complement of identical material in the 46 chromosomes in each cell
       • Meiosis: Process of cell division that forms the gametes; normally results in 23 chromosomes in each human egg and sperm cell rather than the full complement of 46

4. Gene Expression

   • If both parents give the child the same gene its homozygous but if both are different then they are heterozygous or both could be observed leading it to be codominance
     • Homozygous: Genotype in which two alleles of a gene are identical, have the same effect of a trait
     • Heterozygous: Genotype in which two alleles of a gene are different
     • Codominance: Condition in which individual, unblended characteristics of two alleles are reflected in the phenotype.
     • Some genes can affect others leading it to be different than detected
       • Polygenic: Phenotypic characteristic influenced by two or more genes
   • Genomic imprinting:Instances of genetic transmission in which the expression of a gene is determined by whether the particular allelic form has been inherited from the mother or the father