punnett squares. a punnett square illustrates how the parents alleles might combine in offspring. a...
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Punnett SquaresPunnett Squares
Punnett Squares
A Punnett square illustrates how the A Punnett square illustrates how the parents’ alleles might combine in offspring. parents’ alleles might combine in offspring.
The top of the Punnett Square are one of the The top of the Punnett Square are one of the parent’s alleles, the side of the Punnett parent’s alleles, the side of the Punnett square shows the other parent’s alleles for square shows the other parent’s alleles for the trait the trait
HeterozygousHeterozygous: having dissimilar pairs of : having dissimilar pairs of alleles for any hereditary characteristicalleles for any hereditary characteristic
HomozygousHomozygous: having identical pairs of : having identical pairs of alleles for any given pair of heredity alleles for any given pair of heredity characteristicscharacteristics
Mendel’s Laws of Inheritance1. Law of Dominance: In heterozygous genotypes,
dominant alleles hide recessive alleles when both are inherited by an organism. (Hh means the dominant trait will show up in the phenotype)
Mendel’s Laws of Inheritance
1. The Law of Segregation (separation): Each organism has 2 alleles for a gene. Only one allele from each gene pair will be passed on to the offspring.
Homozygous/Heterozygous
Cross a homozygous Cross a homozygous dominant tall plant dominant tall plant with a homozygous with a homozygous recessive short plant. recessive short plant.
What letters would you use to represent this cross?
Dominant trait = tall Dominant trait = tall
Recessive trait = shortRecessive trait = short
T = tall T = tall t = short t = short
Hmzg / Htzg
What is the genotype of a homozygous What is the genotype of a homozygous dominant tall plant?dominant tall plant?
GenotypeGenotype
% % TTTT
% % TtTt
% tt% tt
TT TT
TT x ttTT x tt
What is the genotype of a homozygous What is the genotype of a homozygous recessive short plant?recessive short plant? tt tt
t t
T
T
PhenotypePhenotype
% tall% tall
% % shortshort
Tt Tt
Tt Tt
0
100
0
0
100
2. Cross a heterozygous brown haired rabbit 2. Cross a heterozygous brown haired rabbit with a homozygous recessive white haired with a homozygous recessive white haired rabbit.rabbit.
o What letters would you use to represent this cross?
Dominant trait = Dominant trait = brown hairbrown hair
Recessive trait = Recessive trait =
white hairwhite hair B = brownB = brown b = whiteb = white
What is the genotype of a heterozygous What is the genotype of a heterozygous brown haired rabbit?brown haired rabbit?
GenotypeGenotype
% % BBBB
% % BbBb
% % bbbb
Bb Bb
Bb x bbBb x bb
What is the genotype of a homozygous What is the genotype of a homozygous recessive white haired rabbit?recessive white haired rabbit? bb bb
b b
B
b
PhenotypePhenotype
% % brownbrown
% % whitewhite
bb bb
Bb Bb
0
50
50
50
50
3.. Cross a homozygous dominant 3.. Cross a homozygous dominant long haired guinea pig with a long haired guinea pig with a heterozygous long haired guinea pig.heterozygous long haired guinea pig.
o What letters would you use to represent this cross?
Dominant trait = Dominant trait = long hairlong hair
Recessive trait = Recessive trait =
short hairshort hair L = longL = long l = short l = short
What is the genotype of a homozygous What is the genotype of a homozygous dominant long haired guinea pig?dominant long haired guinea pig?
GenotypeGenotype
% % LLLL
% % LlLl
% ll% ll
LLLL
LL x LlLL x Ll
What is the genotype of a heterozygous What is the genotype of a heterozygous long haired guinea pig?long haired guinea pig? Ll Ll
L l
L
L
PhenotypePhenotype
% long% long
% % shortshort
LL Ll
LL Ll
50
50
0
0
100
4. Cross a heterozygous wrinkly 4. Cross a heterozygous wrinkly elephant with another heterozygous elephant with another heterozygous wrinkly elephant.wrinkly elephant.
What letters would you use to represent this cross?
Dominant trait = Dominant trait = wrinkly skinwrinkly skin
Recessive trait = Recessive trait =
smooth skinsmooth skin W = wrinklyW = wrinkly w = smooth w = smooth
What is the genotype of a heterozygous What is the genotype of a heterozygous wrinkly-skinned elephant?wrinkly-skinned elephant?
GenotypeGenotype
% % WWWW
% % WwWw
% % wwww
WwWw
Ww x WwWw x Ww
What is the genotype of a heterozygous What is the genotype of a heterozygous wrinkly-skinned elephant?wrinkly-skinned elephant? WwWw
W w
W
w
PhenotypePhenotype
% % wrinklywrinkly
% % smoothsmooth
Ww ww
WW Ww
25
50
25
25
75
PhenotypePhenotype
% round% round
% % wrinkledwrinkled
5. A plant that is homozygous dominant for round seeds is crossed with a heterozygous plant. What is the probability that the offspring will have
wrinkled seeds?
RR x RrRR x Rr
R r
R
R
RR Rr
RR Rr
R = round
GenotypeGenotype
% % RRRR
% Rr% Rr
% rr% rr
r = wrinkled
50
50
0
0
100