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ID 16207

Genetic inheritance follows rules.

Description:
Perform a dihybrid cross.
Transcript:
HI! Let's try this problem. We have a pea plant that is heterozygous for two traits — height and seed color. The plant is tall and yellow, which are the dominant phenotypes. We will let this plant self-fertilize, and see what kind of offspring this plant produces. This is a dihybrid cross; we are tracking two traits. We will use T (tall) to denote height and Y (yellow) to denote seed color. The plant is heterozygous for both traits so the plant is TtYy. The first thing to do is determine the types of gametes this plant produces. What types of gametes will a TtYy plant produce? Tt, Yy. No, gametes will not have two alleles of the same trait. TY,Ty,tY,ty. That is correct. T,t,Y,y. No, we're tracking two traits at the same time. TT,tt,YY,yy. No, gametes will not have two alleles of the same trait. So, the gametes are TY, Ty, tY, ty. Remember, this is a self fertilization. The gamete types are the same for both parents. Let's fill out the Punnett square for this dihybrid cross. The offspring genotypes are TTYY, TTYy, TTyy, TtYY, Ttyy, TtYy, ttYY, ttYy, ttyy. Which ones are tall and yellow? Click on one the squares. Remember tall and yellow are dominant phenotypes. How many of these plants, total, are tall and yellow? Click on the dot. 9 There are nine tall/yellow plants. These are their genotypes: TTYY, TTYy, TtYY, TtYy. Which ones are short and yellow? Click on one of the squares. Remember tall and yellow are dominant phenotypes. How many of these plants, total, are short and yellow? Click on the dot. There are three short/yellow plants. These are their genotypes: ttYy, ttYY. Which ones are tall and green? Click on one of the squares. Remember tall and yellow are dominant phenotypes. How many of these plants, total, are tall and green? Click on the dot. There are three tall/green plants. These are their genotypes: TTyy, Ttyy. The types of plants from a dihybrid, heterozygous cross are: Tall and Yellow= 9 Short and yellow = 3 Tall and green = 3 Short and green =1 9:3:3:1 Based on your results, are tall plants always yellow and short plants always green? Tall plants are not always yellow and short plants are not always green. There are tall/green as well as short/yellow plants. The inheritance of one gene does not depend on the inheritance of another. This is Mendel's Law of Independent Assortment. It holds true when the genes are on different chromosomes. CONGRATULATIONS! YOU'RE SO SMART!
Keywords:
genetic inheritance, dihybrid cross, gametes,pea plant, punnett square, phenotypes, genotypes,alleles, heterozygous, dominant, self-fertilize,offspring,9:3:3:1 ratio, law of independent assortment
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