1. TEST CROSSES

2. 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 !

3. 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

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

5. 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

6. 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.

7. 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