Gregor Mendel: An Austrian monk who studied traits in pea plants. He is considered the father of genetics. 1850’s
Allele: One of a number of different forms of a gene.
Trait: A specific characteristic of an individual. Segregation: Se
Principle of Dominance: States that some alleles are Dominant and others are recessive. Gene (Character)
Allele (Trait)
Symbol
Purple
P
White
p
Dominant trait Upper case = _____________________________
Parental P = ___________________
Recessive trait Lower case = _____________________________
Filial F1 = ___________________
Punnett Square 1
Flower color
Round
R
p
r I
Constricted
i
p Pp
eggs
Offspring 1
sperm
i
I
II
Ii
Ii
ii
eggs
Pp
Pod shape
I
P F1
Pp
P Inflated
sperm
Ii Ii ________ x ________
F1
P Wrinkled
Punnett Square 2
pp PP x ________ ________ P
Pea shape
The separation of alleles.
Pp
i
Name ___________________________________
Notes: Mendelian Genetics Gametes:
Period _______ Date ____________ Seat _____
Fertilization:
Sex cells; egg and sperm
The process in sexual reproduction in
which male and female reproductive cells join to form a new cell.
Homozygous: Having two identical alleles for a particular gene. Probability: The likelihood that a particular event will occur
Heterozygous:
Having different alleles for a particular gene.
Calculate the probability for each event below: ii Write the alleles for a homozygous constricted pod________ Rr Write the alleles for a heterozygous round pea ________ No Can you have a white heterozygous flower? ________
Rolling the number 2 on a six-sided die
1/6 ________
In the space below, draw a Punnett square for a cross between two plants that are heterozygous for round peas.
Rolling an even number on a die Rolling a 2 and a 6 with two dice
________ 1/2 ________ 1/36
For the Punnett square on the left, what is the probability that you will have offspring that:
Rr x ________ Rr ________ R
P
sperm
r
have round peas
F1
R
RR
have wrinkled peas is homozygous recessive
Rr
eggs
r
Rr
1/2 Coming up heads with one flip of the coin ________ 1/16 Coming up heads four times in a row ________
rr
is homozygous dominant is heterozyous 2
3/4 or 75% ________ 1/4 or 25% ________ ________ 1/4 or 25% 1/4 or 25% ________ 1/2 or 50% ________
Name ___________________________________
Notes: Mendelian Genetics
Period _______ Date ____________ Seat _____
Phenotype:
Genotype: The genetic makeup of an organism.
The physical characteristics of an organism.
What are the possible genotypes for a plant with…
Draw and label the phenotype for a pea pod that is Ii.
Inflated pod Draw and label the phenotype for a pea seed that is rr. ________
purple flowers
Pp or PP
wrinkled peas
rr
inflated pods
Ii or II
Draw all the possible gametes that can come from plants with the following traits: Constricted pods
Wrinkled seed
One kind of gamete
i
i i
Draw and label the phenotype for a pea plant that is Pp. ________
Heterozyous for round seeds
Two kinds of gametes
R
r
Rr Homozygous for purple flowers
P
Purple flower 3
PP
One kind of gamete
Name ___________________________________
Notes: Mendelian Genetics
Period _______ Date ____________ Seat _____ One-Factor Cross: Flower Color
One-Factor Cross: A genetic cross involving only one gene . For example, the character of flower color.
Pp Pp Genotype ________ x ________ Purple Purple ____________ x ___________ Phenotype P
Independent Assortment: States that genes for different traits can segregate independently when gametes are made.
Two-Factor Cross: A genetic cross involving two genes . For example, the character of flower color and the character of seed shape.
PR
Pr
PR
Pr
PPRR
PPRr
PPRr
PPrr
pR
pr
PpRR
PpRr
PpRr
Pprr
ppRR
ppRr
ppRr
pprr
Offspring Phenotype Purple flower, round seed Purple flower, wrinkled seed White flower, round seed White flower, wrinkled seed
Probability 9 : 16 3 : 16 3 : 16 1 : 16
pR
pr 4
PpRR
PPRr
PpRr
Pprr
Name ___________________________________
Notes: Mendelian Genetics True-Breeding:
Period _______ Date ____________ Seat _____
Organisms that make offspring
Test Cross: A cross between an organism whose genotype for a certain trait is unknown and an organism that is homozygous recessive for that trait so that the unknown genotype can be determined.
identical to themselves.
Mendel had a pea plant that produced inflated pods and round seeds. He wanted to find out if the plant was true-breeding (homozygous) for those traits. To find out, he used Punnett squares to design two test crosses. The probabilities from these Punnett squares would then be compared to actual results from a field test he would conduct in his garden. Inflated Pod Trait If Homozygous
If Heterozygous
If Homozygous
If Heterozygous
ii II ________ x ________
Ii ii ________ x ________
rr RR x ________ ________
rr Rr x ________ ________
i
P
sperm
i
i
Ii
Ii
I
Ii
i
sperm
r
Ii
R
Ii ii
R
sperm
r
F1
Rr
Rr
eggs
ii
r
P
F1
eggs
Ii
r
P
F1
eggs
I
sperm
i
P
F1
I
Round Seed Trait
R
Rr
Rr
rr
rr
eggs
Rr
rr
r
Mendel used his garden to conduct his field study. Mendel crossed the inflated pod, round-seeded plant with a plant that was homozygous recessive for both traits (constricted pods and wrinkled seeds). When the field study was complete, he tallied up the results. His numbers are shown below for the results of the test crosses.
Inflated pods 16
Results of Field Study Test Cross Constricted pods Round seeds 0 43
Wrinkled seeds 41
According to the results of his field study, what was the genotype of his inflated-pod, round-seeded plant? 5
