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Published byClemence Underwood Modified over 9 years ago
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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
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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
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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
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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
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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
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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
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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
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