#50 using a punnett square. homozygous: genotype with identical alleles, same letters (rr =...
DESCRIPTION
What is a PUNNETT SQUARE? A tool to predict the probability of certain traits in offspring that shows the different ways the alleles of each genotype can combine A way to show possible phenotypes & genotypesTRANSCRIPT
#50 Using a Punnett #50 Using a Punnett SquareSquare
Homozygous: Genotype with Identical alleles, same
letters (RR = dominant, rr = recessive)
HeterozygousGenotype with different alleles, but
dominant one shows up (Bb always has the dominant phenotype).
Vocabulary
What is a PUNNETT SQUARE?
• A tool to predict the probability of certain traits in offspring that shows the different ways the alleles of each genotype can combine
• A way to show possible phenotypes & genotypes
What is a PUNNETT SQUARE?• Letters stand for dominant and
recessive alleles– An uppercase letter stands for a
dominant allele – Lowercase letters stand for recessive
alleles
Using a PUNNETT SQUARETo set up a Punnett square, draw a
large square, and then divide it into 4 equal sections (also squares). It should look something like this:
Using a PUNNETT SQUARENow you need two parents to mate,
ones with a known genotype
For example, a red flower (genotype Rr) and a white flower (genotype rr). Rr x rr
Using a PUNNETT SQUAREPlace one of the parents on top, and
one on the left. You should get a something similar to this:
Using a PUNNETT SQUAREFinally, take each letter in each column and
combine it with each letter from each row in the corresponding square. You should now have a picture close to this:
Using a PUNNETT SQUARE• The two-letter combinations are the
possible genotypes of offspring• They are: Rr, Rr, rr, and rr genotypes
• From this it is possible to determine the probability (chance) that a flower will have a red phenotype (2/4 or 50%) or a white phenotype (2/4 or 50%)
1. Cross a homozygous dominant tall plant with a homozygous 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
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
0100
0
0100
#2. Cross a heterozygous brown haired #2. Cross a heterozygous brown haired rabbit with a homozygous recessive white rabbit with a homozygous recessive white haired rabbit.haired rabbit.
o What letters would you use to represent this cross?
Dominant trait = Dominant trait = brown hairbrown hair
Recessive trait = white hairRecessive trait = white 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 long 3. Cross a homozygous dominant long haired guinea pig with a 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
0100
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 = smooth skinRecessive trait = smooth 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