Bio311Dreview - Chapter 13 pg 248 261 Inheritance(heredity...

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Chapter 13. pg. 248 – 261 Inheritance (heredity) – transmission of traits from one generation to the next Variation: offspring differ in appearance from parents and siblings Genetics: scientific study of heredity and hereditary variation Genes: hereditary units parents endow their offspring with that contains coded information Tens of thousands of genes constitute our genome Gametes – animal and plant reproductive cells that transmit genes from one generation to the next Locus – a gene’s specific location along the length of a chromosome (plural, loci) Asexual reproduction – a single individual is the sole parent and passes copies of all its genes to its offspring Ex1. Single celled eukaryotic organism by mitotic cell division (DNA is copied and allocated equally to two daughter cells) Ex2. Hydra (related to jellyfish) by budding. Clone – an individual that reproduces asexually gives rise to a clone; group of genetically identical individuals. Sexual Reproduction – two parents give rise to offspring that have unique characteristics of genes inherited from the two parents Somatic cell – any cell other than a gamete has 46 chromosomes Karyotype – display of chromosomes ordered in pairs Homologous chromosomes (homologues) – have same length, centromere position, and staining pattern XX – female XY – male Only small parts of the X and Y are homologous XY called sex chromosomes; all others called autosomes We inherit one chromosome of each pair form each parent Thus, we have two sets of 23 chromosomes in Diploid cell – cell with two chromosome sets and has diploid number of chromosomes 2n (for humans 2n = 46) Non sister chromatids – any two chromatids in a pair of homologous chromosomes that are not sister chromatids Fertilization – fusion of the nuclei between a haploid ovum from the mother and a haploid sperm cell from the father Zygote – resulting fertilized egg is a diploid because it contains two haploid sets of chromosomes Gametes – only cells of the human body that are not produced by mitosis which develop in the gonads; hapoid cells (n=23) so that our chromosome numbers are not constantly increasing (fixed through meiosis) Meiosis occurs during the production of gametes, which undergo no further cell division prior to fertilization. The diploid zygote divides by mitosis, producing a multicellular organism that is diploid.
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Alternation of generations – some plant and algae experience a life cycle that includes both diploid and haploid multicellular stages Sporophyte – multicellular diploid stage; meiosis in this stage produces haploid cells called spores; spores give rise to multicellular individuals without fusing with another cell by dividing mitotically to generate a multicellular haploid stage called the gametophyte.
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