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b3 (chromosomes, genes = heritable factor that consists of a sequence of
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b3
chromosomes
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homologous = paired chromosomes inherited from
both parents, genes are at the same loci but alleles may differ
sex determination
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23rd pair are sex chromosomes (females XX, males XY), as Y makes male characteristics depends on if sperm is carrying x or y
karyotypes identify the number and types of chromosomes in a cell, performed pre-natally to identify the sex of offspring or diagnose potential chromosome abnormalities
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meiosis = reduction division of a diploid cell to produce four haploid cells (gametes) that are genetically distinct
meiosis 1 separates homologous chromosomes, meiosis 2 separates sister chromatids
crossing over
- via synapsis in prophase 1 - homologous chromosomes form bivalents - at chiasmata, genetic info is exchanged between homologous pair - non-sister chromatids which have exchanged DNA = recombitants
random assortment = e homologous pairs orient randomly in Metaphase I = equal chance of a resulting gamete
containing either the maternal or paternal chromosome
nondisjunction = chromosomes failing to separate,
resulting in gametes with extra or missing chromosomes
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