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 If you get some deaf puppies, you know parent genotype was Dd NOT DD.

DRAGONS FF Ff Firebreathing (F) in dragon is a dominant trait http://www.webweaver.nu/clipart/dragons3.shtml Firebreathing (F) in dragon is a dominant trait NON-firebreathing (f) is recessive. A firebreathing dragon could have 2 possible GENOTYPES ______ ______ How do we tell which one it is? FF Ff

TESTCROSS FIREBREATHING PARENT WITH NON-FIREBREATHER F F F f f Fire Fire Fire Fire Fire NO Fire NO f If you get some NON-fire breathing dragons you know parent genotype was Ff NOT FF.