Lecture 3 - Lecture III The chromosomal basis of inheritance Lecture Takehome messages Chromosome theory of inheritance eukaryotic chromosomes are

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Lecture III: The chromosomal basis of inheritance Lecture III: The chromosomal basis of inheritance Takehome messages: Chromosome theory of inheritance: eukaryotic chromosomes are transmitted during cell division by mitosis and during reproduction by meiosis meiosis explains Mendel’s Laws Non-disjunction elucidates the modes of sex determination (X:autosome balance vs. Y) in flies and humans, respectively Sex-linkage of traits support the chromosomal theory of inheritance and show sex chromosomes carry genes not related to sex.
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Key terms to know Key terms to know aneuploidy autosomes Barr body crisscross inheritance dosage compensation environmental sex determination genotypic sex determination hemizygous hermaphroditic heterogametic sex holandric trait homogametic sex karyotype Klinefelter syndrome Lyon hypothesis nondisjunction primary nondisjunction secondary nondisjunction sex chromosomes sex linked Turner syndrome X chromosome– autosome balance system X-linked recessive trait Y chromosome mechanism of sex determination
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Chromosomes and Chromosomes and Cellular Reproduction Cellular Reproduction Most sexually reproducing organisms Most sexually reproducing organisms are diploid (2n); some simple are diploid (2n); some simple organisms spend most of their time as organisms spend most of their time as haploids (e.g. fungi, mosses) haploids (e.g. fungi, mosses) At the turn of the 20 At the turn of the 20 th th century, much century, much was known about the movement of was known about the movement of chromosomes in mitosis and meiosis, chromosomes in mitosis and meiosis, and that different organisms had their and that different organisms had their own complement, yet there was own complement, yet there was essentially no understanding of their essentially no understanding of their role in inheritance. role in inheritance. Two years after the rediscovery of Two years after the rediscovery of Mendel’s work, Sutton and Boveri Mendel’s work, Sutton and Boveri (1902) independently realized the (1902) independently realized the parallel between Mendelian inheritance parallel between Mendelian inheritance and chromosome transmission, and and chromosome transmission, and proposed the proposed the chromosome theory of chromosome theory of inheritance inheritance Pea: 14 Pea: 14
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Eukaryotic Chromosomes Eukaryotic Chromosomes Chromosome pairs in diploid organisms are homologous chromosomes. One member of each pair (homolog) is inherited from each parent. Chromosomes that have different genes and do not pair are non-homologous chromosomes . Animals and some plants have male and female
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Lecture 3 - Lecture III The chromosomal basis of inheritance Lecture Takehome messages Chromosome theory of inheritance eukaryotic chromosomes are

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