SECTION
6,5
TRAITS AND PROBABILITY
Study Guide
KEY CONCEPT
The inheritance of traits
follows the rules of
probabilÍty.
monohybrid
of ind e pendent
assortment
testc ross
nnett square
cross
di
cr0ss
robability
MAIN IDEA: Punnett squares illustrate
genetic crosses.
Identify what each of the numbered parts represents in the Punnett square below. Then draw
lines from each of the parents' alleles to the corresponding alleles in the offspring.
Aa
A AA Aa
f '.,'pnænfg,allele+,
:,
oenotvoe
a.
3.
a
Aa
possible genotypes of
aa
Why does each parent contribute only one allele to the offspring?
>
c
o
o
E
o
Q
C
E
c
o
MAIN IDEA: A monohybrid cross involves one trait.
5. You know a ratio is a comparison that tells how two or more things
relate. What is a
genotypic rutio? a phenotypic ratio?
ro)
f
-o
o
tells the propoñion of offspring that have a particular phenotype
.ts
J
õo)
f
o
ô
6.
What is the genotypic ratio of the offspring in Figure 6.15?
C)
o
E
.9
o
1'2.1
7. What is the phenotypic ratio of the offspring in Figure 6,15?
o
O
Unit 3 Resource Book
McDougal Liltell Biology
Study
Guide 17
Name
Period
Date
STUDY GUIDE, CONTINUED
MAIN IDEA: A dihybrid cross involves two traits.
8. What is a dihybrid cross?
9.
,:
n
'
',
,
Why does eaoh parent organism in the F¡ géneration have four alleles listed in Figure
6.t7?
akes
10. 3"lllferigsrÊ[ili".åi
from this allele
f
had the'genotype AABb. what two types ôf gametes could resutt
combination?
iì
1. lVhat is the phenotypic ratio that results from
a dihybrid cross between two organisms
6 . I 7 for help .
that are heterozygous for both traits? See Figure
MAIN IDEA: Heredity patterns can be calbutated rúitt p"onlbility.
fZ. probäbilitypredictsthe' o,rorag",,
numberôfoccurrences,notthe
:numberofb-ccurrenceó:
13.
To caloulate the probability that two independerrt events
multiply
the proþability
14. In Figure 6.18, the probability of getting
tails up
-o,f
1'"
will happen together,
each individual event,
one coin that is heads up and one eoin that is
*
c
6
is one-for,rrth
ct
E
o
O
:
.s
E
Vocabulary Chêck
co
15. What is a testcross?
cE)
=
o
I
l6¡
18
oenotvoe.
What ís independent in the law
study Guide
=o
F
2
assortment?
Unit
3
Besource Book
McDougal
Littell Biology