Title: Review
1Review
- Monohybrid Dihybrid Crosses
2DOMINANT/RECESSIVE
Dominant
- _____________ allele is represented by a
____________ letter.(usually the first letter of
the trait) - ____________ allele is represented by the SAME
- _________________ letter.
- EX Tall ______
- Short ______
capital
Recessive
lower-case
T
t
NOT S for short
3HOMOZYGOUSHETEROZYGOUS
- When both alleles in the pair are the _______,
the organism is _______________ or
__________ - EX ____ or ___
- When both alleles in the pair are _____________,
the organism is - _________________ or _____________
- Ex ____
SAME
HOMOZYGOUS PURE
TT tt
DIFFERENT
HETEROZYGOUS HYBRID
Tt
4PHENOTYPE/GENOTYPE
- The ________________ of an organism is its
_____________ - The ____________of an organism is
- its _____________
genetic makeup
GENOTYPE
appearance
PHENOTYPE
5MAKING A CROSS for only a __________ trait
____________________
ONE GENE
MONOHYBRID CROSS
- A Punnett square for a MONOHYBRID CROSS looks
like this
6PUNNETT SQUARES
- are used to show possible offspring from a cross
between 2 parents
_______________ go at top and on left
side Boxes show _______________________________
Parent alleles
T T
T t
possible offspring combinations
7STEPS FOR MAKING CROSSES
Figure out parent alleles Choose
Punnett size Put in
parent gametes Fill in offspring
combinations probabilities
phenotypes
genotypes
1. ___________ what _________________ are 2.
________correct__________ square __________ 3.
______ possible_______________________ 4. ______
boxes with _____________________ 5. Determine
____________of_____________
____________
8IN PEA PLANTS
- Tall is dominant over short
- TALL ____
- SHORT ____
T
t
LETS MAKE A CROSS! PURE TALL PURE
SHORT
X
9PURE TALL parentWhat are the parent alleles?
HOMOZYGOUS
?
?
What gametes can it make?
T
T
10PURE SHORT parent What are the parent alleles?
HOMOZYGOUS
?
?
What gametes can it make?
t
t
11ALL
- _____ of the offspring
- ____
- ___/4
- will be
T t
T t
100
4
T t
T t
Tt
TALL
GENOTYPE _____ PHENOTYPE _______
12HYBRID TALL parent What are the parent alleles?
HETEROZYGOUS
?
?
What gametes can it make?
T
t
13T
t
- GENOTYPES
- ¼ _____
- ½ _____
- ¼ _____
TT
T
T t
T T
Tt
tt
T t
t t
t
75
3/4
TALL
PHENOTYPES ____ or ____ _________
____ or ____ _________
1/4
SHORT
25
14PRACTICE MAKING GAMETES for a MONOHYBRID CROSS
R
Tall ____ Round seeds ___ Short
____ Wrinkled seeds ___
T
t
r
15What are the possible gametes?
- Homozygous Tall parent
- What gametes can it produce?
T T
?
?
T
T
16What are the possible gametes?
- PURE wrinkled parent
- What gametes can it produce?
rr
?
?
r
r
17What are the possible gametes?
- Heterozygous Round parent
- What gametes can it produce?
R r
?
?
R
r
18What are the possible gametes?
- Hybrid Tall parent
- What gametes can it produce?
Tt
?
?
T
t
19DIHYBRID CROSSES
http//mac122.icu.ac.jp/BIOBK/BioBookgenintro.html
20- Mendel also asked the question?
- Does the gene that determines if a seed
- is round or wrinkled have anything to
- do with the gene for seed shape?
- Must a seed that is yellow
- also be round?
21MAKING A CROSS with ___________________________
____________
TWO gene traits
DIHYBRID CROSS
- A Punnett square for a DIHYBRID CROSS looks like
this
22Figure 11-10 Independent Assortment in Peas
Section 11-3
23LETS MAKE A DIHYBRID CROSS
HOMOZYGOUS GREEN WRINKLED
rryy
RRYY
1. ___________ what _________________ are 2.
________correct__________ square __________ 3.
______ possible_______________________ 4. ______
boxes with _____________________ 5. Determine
____________of_____________
____________
Figure out parent alleles Choose
Punnett size Put in
parent gametes Fill in offspring
combinations probabilities
phenotypes
genotypes
24- LAW OF __________________________
- the factors are distributed to gametes
independently of other factors
INDEPENDENT ASSORTMENT
Image modified from http//anthro.palomar.edu/me
ndel/mendel_1.htm
25PRACTICE MAKING GAMETES
WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN
MAKE?
HOMOZYGOUS ROUND YELLOW
Each gamete shouldget one of each kindof gene
R R Y Y
R Y
R Y
R Y
R Y
___________ ____________ _____________
_____________
26PRACTICE MAKING GAMETES
WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN
MAKE?
Each gamete shouldget one of each kindof gene
HOMOZYGOUS WRINKLED GREEN
r r y y
r y
r y
r y
r y
___________ ____________ _____________
_____________
27PRACTICE MAKING GAMETES
WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN
MAKE?
HETEROZYGOUSROUND YELLOW
Each gamete shouldget one of each kindof gene
R r Y y
R Y
r y
r Y
R y
___________ ____________ _____________
_____________
28RrYy RrYy RrYy RrYy RrYy RrYy RrYy
RrYy RrYy RrYy RrYy RrYy RrYy
RrYy RrYy RrYy
RrYy
100 of offspring _______ genotype
_______________________ phenotype
ROUND YELLOW
29MAKE ANOTHER CROSS
HETEROZYGOUSROUND YELLOW
HETEROZYGOUSROUND YELLOW
X
R r Y y
R r Y y
30POSSIBLE PARENT GAMETES?
RY
Ry
ry
ry
31____ Round Yellow ____ Round
green ____ Wrinkled
yellow ____ wrinkled green
9
RRYY RRYy RrYY RrYy RRYy RRyy RrYy
RryyRrYY RrYy rrYY rrYy RrYy Rryy
rrYy rryy
3
3
1
heterozygous dihybrid
Sign of a ______________________ cross is
a _____________ ratio in offspring.
9331
329
____ ____________ TRAIT 1 ____________ TRAIT
2 ____ ____________ TRAIT 1
_____________ TRAIT 2 ____ ____________ TRAIT
1 _____________ TRAIT 2 ____ ____________
TRAIT 1 _____________ TRAIT 2
dominant dominant
3
dominant recessive
3
recessive dominant
1
recessive recessive
__________ratio is a clue that its a
____________________________cross
9331
HETEROZYGOUS TWO gene
33PRACTICE MAKING GAMETESfor DIHYBRID CROSSES
http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
BioBookTOC.html
34What are the possible gametes?
R R T T
- pure round pure tall __________
-
- ____ ____ _____ ______
- What gametes can it produce?
?
?
?
?
R T
R T
R T
R T
35What are the possible gametes?
T t R R
- Heterozygous Tall __________
- pure round
-
- ____ ____ _____ ______
- What gametes can it produce?
?
?
?
?
T R
T R
t R
t R
36What are the possible gametes?
T t r r
- Hybrid tall __________
- pure wrinkled
-
- ____ ____ _____ ______
- What gametes can it produce?
?
?
?
?
T r
T r
t r
t r
37What are the possible gametes?
T t R r
- Heterozygous tall __________
- hybrid round
-
- ____ ____ _____ ______
- What gametes can it produce?
?
?
?
?
T R
T r
t r
t R
38The Law of Dominance In a cross of parents that
are pure for contrasting traits, only one form of
the trait will appear in the next generation.
Offspring that are hybrid for a trait will have
only the dominant trait in the phenotype. The
Law of Segregation During the formation of
gametes (eggs or sperm), the two alleles
responsible for a trait separate from each
other. Alleles for a trait are then "recombined"
at fertilization, producing the genotype for the
traits of the offspring. The Law of Independent
Assortment Alleles for different traits are
distributed to sex cells ( offspring)
independently of one another.
39MENDEL'S GENETIC LAWS Summary
LAW PARENT CROSS OFFSPRING
DOMINANCE TT x tt tall x short 100 Tt tall
SEGREGATION Tt x Tt tall x tall 75 tall 25 short
INDEPENDENT ASSORTMENT RrGg x RrGg round green x round green 9/16 round seeds green pods 3/16 round seeds yellow pods 3/16 wrinkled seeds green pods 1/16 wrinkled seeds yellow pods