Transcript Notes #11: Mendel's Conclusion

Mendel’s Conclusion
Notes #11
Mendel’s Conclusion
1. Inheritance Patterns: Determined by genes
that are passed on from parent to offspring
2. Law of Dominance: When two genes are
involved, there is one that is more dominant
over the recessive
3. Laws of Segregation: 2 copies of the gene
separate from each other to form gamete
cells.
Ex. Trait: Eye Color (Brown vs blue)
Homozygous
Brown eye male
BB
B
x
Homozygous
blue eye female
bb
Segregation
of genes
B
b
b
Mendel’s Conclusion Cont’d
4. Law of Independent Assortment (Involves 2 Different traits):
- Genes separate randomly and independently from each other.
Ex. Characteristics
Eye Color
Wing color
Traits
Red dominant to White
Allele (Symbol)
R=Red; r=white
Black dominate to White B=Black; b=white
a. What is the genotype of a heterozygous Red Eyed &
Black Winged Fly?
ANS: RrBb
b. What gene combination will result in the gamete
cells from the heterozygous fly?
ANS:
RrBb
RB
Rb
rB
rb
c. Which law does this show?
ANS: Law of Segregation
TWO FACTOR (DIHYBRID) CROSSES
In fruit flies, wings are dominant over no wings. Red eyes are
dominant over yellow eyes. Two flies which are heterozygous
for both traits are mated together. What are the phenotypic
and genotypic ratios for this cross?
x
?
STEP 1: Assign symbol for the traits
Wings: N
No wings: n
Red eyes: R Yellow eyes: r
STEP 2: Determine Genotype of organism
Both are heterozygous for both traits (Wings w/red eyes)
RrNn
x
RrNn
STEP 3: Determine genotype of gamete cells
RrNn
RN
Rn
rN
rn
Gamete Cells
STEP 4: Make a Punnett Square for the cross
RN
Rn
rN
rn
RN
RRNN
RRNn
RrNN
RrNn
Rn
RRNn
RRnn
RrNn
Rrnn
rN
RrNN
RrNn
rrNN
rrNn
rn
RrNn
Rrnn
rrNn
rrnn
STEP 5: Determine the Genotypic and Phenotypic Ratios
Phenotypes
#
___9__
Red Eyes & With Wings:
Red Eyes & No Wings:
__3___
Yellow Eyes & With Wings:
Yellow Eyes & With Wings:
__3___
___1__
We’re going to count off into 4’s
#1s: Tally up the # of Yellow Eyes & With Wings
#2s: Tally up the # of Red Eyes & No Wings
#3s & 4s: Tally up the # of Red Eyes & With Wings
Break off into your lab groups, once you get your #’s
call Ms. Ng over to check and stamp your work.
Ex. Ms. Ng’s Job
Tally up # of Yellow Eyes & No Wings: 1
•
Phenotype Ratio
•
9Red Eyes/Normal Wings
•
3 Red Eyes/No wings
•
3 Yellow Eyes/ Normal Wings
•
1 Yellow Eyes/ No wings