Chapter 4 - BB (1)

Recessive in allele females females genotype

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Unformatted text preview: gene Allele B behaves as dominant in males, but recessive in Allele females females Genotype Phenotype Phenotype Phenotype Phenotype in Females in Males in BB BB bald bald Bb Non bald bald bb Non bald Non bald Pattern baldness - to the level of male sex hormones In females, a rare tumor of the adrenal gland can cause the In secretion of large amounts of male sex hormones secretion Sex limited Traits Sex Traits that occur in only one of the two sexes humans – Breast development is normally limited to females – Beard growth is normally limited to males Beard Feather plumage in chicken The pattern of hen-feathering - production of sex The hormones hormones single ovary is surgically removed from a newly hatched single hh female hh – cockerel-feathering , indistinguishable from a male Genotype Phenotype Phenotype in Females in Phenotype Phenotype in Males hh hh hen-feathered cockerel-feathered Hh hen-feathered hen-feathered HH hen-feathered hen-feathered Lethal Alleles Lethal Essential genes are those that are absolutely required for Essential survival survival Nonessential genes are those not absolutely required for survival survival A lethal allele is one that has the potential to cause the death lethal of an organism Many lethal alleles prevent cell division Some lethal allele exert their effect later in life – Huntington disease Conditional lethal alleles - Temperature-sensitive (ts) lethals Temperature-sensitive Semi lethal alleles – kill some individuals not all Semi kill Semi lethal alleles – Kill some individuals in a population, not all – Environmental factors and other genes - prevent the Environmental detrimental effects of semilethal genes A lethal allele may produce ratios - deviate from Mendelian lethal ratios ratios Non-Manx – Carries a dominant mutation that affects the spine – This mutation shortens the tail Pleiotropic eff...
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