 Living organisms are distinguished by their ability to reproduce their own kind - oaks make oaks - elephants make more elephants  Heredity – transmission of traits from one generation to the next  Genetics – the study of heredity or how traits are passed and the variation that occurs

 Genes – hereditary units with coded information of traits passed from the parents - program the specific traits that emerge as we develop from fertilized eggs to adults *locus – specific location of a gene along the length of a chromosome  Gametes – reproductive or sex cells that are the vehicles that transmit genes from one generation to the next

 Asexual reproduction – single individual is the sole parent and passes exact copies of its genes to offspring - utilize mitotic cell division - genetically identical to parent or clone of genes  Sexual reproduction – two parents contribute unique combinations of genes to the offspring - meiosis - random variation of traits blended from each parent

 Life cycle – generation to generation sequence of stages in reproductive history of an organism  Somatic cells or normal body cells have 46 chromosomes -23 pairs or 22 pairs of autosomes and 1 pair of sex chromosomes  Karyotype – ordered display of chromosomes pairs from longest to shortest

 Homologous or homologues – two chromosomes of same length, centromere position, & staining pattern of genes  Diploid cells – two chromosome sets - 23 pairs or 46 chromosomes - somatic cells  Haploid cells – one chromosome set - 23 chromosomes - gametes

 Fertilization – union of haploid sperm cell with haploid ovum to produce diploid offspring zygote – fertilized egg that contains 2 sets of chromosomes with genes contributed from each parent  Meiosis – gametic cell division that reduces the number of chromosome sets from two to one  In animals, fertilization and meiosis alternate in sexual life cycles offsetting each other’s effects on chromosome number

 All sexually reproducing organisms alternate between fertilization and meiosis, but timing of the events can vary  Alternation of generations – life cycle that includes both diploid and haploid multicellular stages -Plants,fungi, protists, and some algae undergo mitosis after meiosis to produce a haploid individual. -haploid cell uses mitosis to produce haploid gametes that fuse in fertilization for diploid offspring