TEST CROSSES

TESTCROSS used to tell what genes an organism has Example: The genes of a TALL PARENT are UNKNOWN - COULD HAVE _____ TT Tt BOTH LOOK ALIKE ! http://mac122.icu.ac.jp/BIOBK/BioBookgenintro.html

TESTCROSS used to tell what genes an organism has Cross an UNKNOWN parent with a ____________________________ and see results Offspring give a clue about the unknown parent’s genes HOMOZYGOUS RECESSIVE

TESTCROSS Tt tt t Tt Tt 50% will be TALL All offspring will 50% will be SHORT All offspring will be TALL

DEAF DOGS Deafness in dogs is caused by a recessive allele. Deaf dogs have the genotype dd. A HEARING dog could have 2 possible GENOTYPES ______ ______ How do we tell which one it is? Dd DD

TESTCROSS HEARING PARENT WITH DEAF PARENT D D D d d Hear Hear Hear Deaf Hear Deaf d deaf If you get some _______ puppies, you know parent genotype was Dd NOT DD.

d Hear Hear What if ALL the puppies can HEAR? BOTH COULD MAKE D D D d d Hear Hear Hear Hear d Hear Deaf What if ALL the puppies can HEAR? BOTH ________Dd and DD parents ________________ Hearing dogs CAN’T tell genotype of unknown parent; NEED TO DO ANOTHER _________________ COULD MAKE TESTCROSS