Mississippi Science GEN.4.5
The Standard
- GEN.4
- Students will analyze and interpret data collected from probability calculations to explain the inheritance of traits within a population.
Enrichment: Construct maps of genes on a chromosome based on data obtained from 2- and/or 3-point crosses or from recombination frequencies.
2026 Mississippi College- and Career-Readiness Standards for Science · Classic Mendelian Genetics
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students identify parental and recombinant offspring from a genetic cross. They use the counts to estimate distances between genes and place the genes in order on a chromosome map.
What Mastery Looks Like
- Given 20 recombinant offspring out of 200, a student calculates a distance of 10 map units. For a three-gene cross, they identify the middle gene and count double crossovers in both intervals.
Common Misconceptions
- Students may mistake the most common offspring types for recombinants. They may miss double crossovers because the outer genes look like the parental types. Some treat recombination frequency as the chance of having a trait.
How to Assess It
- Exit ticket: A testcross yields 42 AB, 42 ab, 8 Ab, and 8 aB offspring. Ask students to identify the parental types, calculate recombination frequency, and label a two-gene map.
Lesson moves
Ways to Teach It
Give pairs paper gene cards marked A-B 4%, B-C 7%, and A-C 11%; have them tape the cards into a chromosome map.
Ask students to explain in three sentences why genes with 4% recombination are likely closer than genes with 20% recombination.
Play map match: teams pair offspring-count cards showing 5, 10, or 20 recombinants out of 100 with the correct map distances.
Show a seed breeder's resistance gene and markers 2 and 18 map units away; ask which marker would better track resistance.
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Printable GEN.4.5 Worksheet
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