Transcript white wolf
Monohybrid Test Cross Human Genetic Traits Monohybrid Test Cross monohybrid cross: focuses on one inherited trait test cross: used to determine the genotype of a dominant phenotype Example: White fur is dominant over gray in wolves. Determine whether a white wolf is a purebred or a hybrid. Monohybrid Test Cross Let W = white phenotype w= gray genotypes white WW homozygous dominant purebred white white Ww heterozygous hybrid gray ww homozygous recessive purebred gray Monohybrid Test Cross w w Case 2 Ww x ww white white W W W gray gray Case 1 WW x ww w w w Monohybrid Test Cross gray 100% white W W w Ww Ww w Ww Ww Case 2 Ww x ww white 50% white W 50% gray gray Case 1 WW x ww white w w Ww ww w Ww ww Conclusion: To find out the genotype of a dominant phenotype: 1. Cross it with a homozygous recessive genotype 2. If any recessive phenotypes are produced, the parent must be heterozygous Human Genetics most genetic disorders are associated with a mutant recessive allele fortunately to show symptoms of the disorder a person must inherit a mutant allele from each parent i.e. must have 2 mutant alleles: recessive i.e. genotype: homozygous ________________ most people carry about 30 - 40 mutant alleles, but have only one allele for each trait, so it is covered up by the other normal dominant allele family members have high probability of carrying the same mutant alleles marrying a close relative increases the chance of an offspring getting 2 mutant alleles, i.e. (have the abnormal phenotype) Human Genetics Example: Thalassemia is a blood disorder that affects hemoglobin. It is caused by a mutant recessive allele. Let: H – normal hemoglobin h – abnormal hemoglobin Possible Genotypes Possible Phenotypes HH homozygous dominant normal Hh heterozygous normal (carrier) hh homozygous recessive thalassemia Mendelian Genetics heterozygous Practice: If two carriers have a child, what is the probability that their child will have Thalassemia? Hh x H H h Hh h Genotypes? Phenotypes? Mendelian Genetics heterozygous Practice: If two carriers have a child, what is the probability that their child will have Thalassemia? Hh x Hh Genotypes: H h 25 % homozygous dominant 50 % heterozygous H h H H H h H h 25 % homozygous recessive h h Phenotypes: 25 % have disorder 75% normal Homework Textbook Problems • Page 139 # 1-5