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Title: Review


1
Review
  • Monohybrid Dihybrid Crosses

2
DOMINANT/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
3
HOMOZYGOUSHETEROZYGOUS
  • 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
4
PHENOTYPE/GENOTYPE
  • The ________________ of an organism is its
    _____________
  • The ____________of an organism is
  • its _____________

genetic makeup
GENOTYPE
appearance
PHENOTYPE
5
MAKING A CROSS for only a __________ trait
____________________
ONE GENE
MONOHYBRID CROSS
  • A Punnett square for a MONOHYBRID CROSS looks
    like this

6
PUNNETT 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
7
STEPS 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_____________
____________
8
IN PEA PLANTS
  • Tall is dominant over short
  • TALL ____
  • SHORT ____

T
t
LETS MAKE A CROSS! PURE TALL PURE
SHORT
X
9
PURE TALL parentWhat are the parent alleles?
  • T T _________

HOMOZYGOUS
?
?
What gametes can it make?
T
T
10
PURE SHORT parent What are the parent alleles?
  • t t _________

HOMOZYGOUS
?
?
What gametes can it make?
t
t
11
ALL
  • _____ of the offspring
  • ____
  • ___/4
  • will be

T t
T t
100
4
T t
T t
Tt
TALL
GENOTYPE _____ PHENOTYPE _______
12
HYBRID TALL parent What are the parent alleles?
  • T t _________

HETEROZYGOUS
?
?
What gametes can it make?
T
t
13
T
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
14
PRACTICE MAKING GAMETES for a MONOHYBRID CROSS
R
Tall ____ Round seeds ___ Short
____ Wrinkled seeds ___
T
t
r
15
What are the possible gametes?
  • Homozygous Tall parent
  • What gametes can it produce?

T T
?
?
T
T
16
What are the possible gametes?
  • PURE wrinkled parent
  • What gametes can it produce?

rr
?
?
r
r
17
What are the possible gametes?
  • Heterozygous Round parent
  • What gametes can it produce?

R r
?
?
R
r
18
What are the possible gametes?
  • Hybrid Tall parent
  • What gametes can it produce?

Tt
?
?
T
t
19
DIHYBRID CROSSES
  • (2 traits)


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?

21
MAKING A CROSS with ___________________________
____________
TWO gene traits
DIHYBRID CROSS
  • A Punnett square for a DIHYBRID CROSS looks like
    this

22
Figure 11-10 Independent Assortment in Peas
Section 11-3
23
LETS MAKE A DIHYBRID CROSS
  • HOMOZYGOUS
  • YELLOW ROUND

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
25
PRACTICE 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
___________ ____________ _____________
_____________
26
PRACTICE 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
___________ ____________ _____________
_____________
27
PRACTICE 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
___________ ____________ _____________
_____________
28
RrYy RrYy RrYy RrYy RrYy RrYy RrYy
RrYy RrYy RrYy RrYy RrYy RrYy
RrYy RrYy RrYy
RrYy
100 of offspring _______ genotype
_______________________ phenotype
ROUND YELLOW
29
MAKE ANOTHER CROSS
HETEROZYGOUSROUND YELLOW
HETEROZYGOUSROUND YELLOW
X
R r Y y
R r Y y
30
POSSIBLE 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
32
9
____ ____________ 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

33
PRACTICE MAKING GAMETESfor DIHYBRID CROSSES
http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
BioBookTOC.html
34
What 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
35
What 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
36
What 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
37
What 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
38
The 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.
39
MENDEL'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
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