Transcript TEST CROSSES TESTCROSS used to tell what genes an organism has Example: The genes of a TALL PARENT are UNKNOWN - COULD HAVE _____ TT Tt -

TEST CROSSES
TESTCROSS
used to tell what genes an organism has
Example: The genes of a TALL
PARENT are UNKNOWN
- COULD HAVE _____
TT
Tt
- COULD HAVE _____
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
____________________________
HOMOZYGOUS RECESSIVE
and see results
Offspring give a clue about the
unknown parent’s genes
TESTCROSS
T
T
t
t Tt
Tt
t Tt
tt
Tt
t
Tt
t
tt
T
All offspring will
be TALL
Tt
50% will be TALL
50% will be SHORT
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
Dd
DD
______
______
How do we tell which one it is?
TESTCROSS
HEARING PARENT WITH DEAF PARENT
D
D
d
Hear
Hear
d
d
Hear
Hear
d
D
d
Hear
Deaf
Hear
Deaf
If you get some deaf puppies, you know
parent genotype was Dd NOT DD.
http://www.webweaver.nu/clipart/dragons3.shtml
DRAGONS
Firebreathing (F) in dragon
is a dominant trait
NON-firebreathing (f) is recessive.
A firebreathing dragon could have 2
possible GENOTYPES
FF
Ff
______
______
How do we tell which one it is?
TESTCROSS
FIREBREATHING PARENT WITH NON-FIREBREATHER
F
F
f
Fire
Fire
f
f
Fire
Fire
f
F
f
Fire
NO
Fire
NO
If you get some NON-fire breathing dragons
you know parent genotype was Ff NOT FF.