IB Biology Topic D3.2.17 Punnett Grids for Predicting Genotypic and Phenotypic Ratios in Dihybrid Crosses Revision Notes (HL)

IB Biology Topic D3.2.17 Punnett Grids for Predicting Genotypic and Phenotypic Ratios in Dihybrid Crosses Revision Notes (HL) | RevisionDojo

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A Dihybrid Cross Tracks Two Traits and Gives a 9:3:3:1 Ratio

Mendel's pea experiments showed that traits are inherited independently when controlled by unlinked genes.
A dihybrid cross follows two traits at once, and the principle of independent assortment produces a distinctive phenotypic ratio in the offspring.

Building the 4×4 Punnett Grid in Five Steps

Step 1: Determine parental genotypes
1. Here both parents are heterozygous ($RrYy$).
Step 2: Identify the gametes
1. Each parent makes four gamete types using the FOIL method: First ($RY$), Outer ($Ry$), Inner ($rY$), Last ($ry$).

Tip

Write the gametes clearly along the top and side of the grid to avoid confusion.

Step 3: Draw the Grid

Construct a 4×4 grid, one parent's gametes across the top and the other down the side.

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Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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A Dihybrid Cross Tracks Two Traits and Gives a 9:3:3:1 Ratio

Mendel's pea experiments showed that traits are inherited independently when controlled by unlinked genes.
A dihybrid cross follows two traits at once, and the principle of independent assortment produces a distinctive phenotypic ratio in the offspring.

Building the 4×4 Punnett Grid in Five Steps

Step 1: Determine parental genotypes
1. Here both parents are heterozygous ($RrYy$).
Step 2: Identify the gametes
1. Each parent makes four gamete types using the FOIL method: First ($RY$), Outer ($Ry$), Inner ($rY$), Last ($ry$).

Tip

Write the gametes clearly along the top and side of the grid to avoid confusion.

Step 3: Draw the Grid

Construct a 4×4 grid, one parent's gametes across the top and the other down the side.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic D3.2.17: Punnett Grids for Predicting Genotypic and Phenotypic Ratios in Dihybrid Crosses Notes

A Dihybrid Cross Tracks Two Traits and Gives a 9:3:3:1 Ratio

Building the 4×4 Punnett Grid in Five Steps

Step 3: Draw the Grid

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

A Dihybrid Cross Tracks Two Traits and Gives a 9:3:3:1 Ratio

Building the 4×4 Punnett Grid in Five Steps

Step 3: Draw the Grid

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics