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Karyotyping BSC 2010L
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Humans Haploid # of chromosomes: 23 Diploid #: 46 Remember:
Have 23 pairs 1 of each pair came from mom 1 of each pair came from dad Note that we have 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes
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Dominant vs. Recessive Traits
Each pair of chromosomes is referred to as HOMOLOGOUS CHROMOSOMES Have the same genes For each gene there can be 2 alleles (different forms) Look at picture below: B = brown eyes b = blue eyes Brown is dominant so this person’s phenotype would be brown eyes
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Dominant vs. Recessive Traits
Incomplete Dominance Form of inheritance where heterozygous alleles are both expressed, combined phenotype Example: a plant with white flowers and plant with red flowers has offspring with pink flowers Codominant Both alleles are expressed Example: Blood types in humans If a person has the A allele and the B allele, then both A and B are expressed on the surface of the red blood cell
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Sex-linked Genes Genes located on the sex chromosomes (23rd pair in humans) Examples: Color-blindness Hemophilia Males only need 1 gene on X chromosome to have trait – look at boy on far right
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