Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Punnett Square Notes A Punnett Square is a grid for organizing genetic information. It is VERY similar to how you predict probability. A punnett square indicates the PROBABILITY of what the offspring from two individuals will look like. So how do we determine what are the possibilities of the offspring between two hybrid tall pea plants? First: What is the genotype (alleles) for a hybrid tall pea plant? Tt Second: What alleles can one parent possibly give to their offspring? T or t Third: What alleles can the other parent give to their offspring? T or t • Place each allele at the top (male) or side (female) of the punnett square. T T t t • Fill in the punnett square by reading the alleles down & across. T t T TT T t t T t tt • The squares represent the possible genotypes of the offspring from these two individuals. It does NOT mean that there are four offspring. T t T TT T t t T t tt • The square has just given you a probability of getting traitsTT Tt tt T t T TT T t t T t tt • Probability of having a tt offspring (phenotype = short) = 25% or 1 out of 4 • Probability of having a Tt offspring (phenotype = tall) = 50% or 2 out of 4 • Probability of having a TT offspring (phenotype = tall) = 25% or 1 out of 4 • What are the offspring possibilities between a hybrid widow peaked dad and a non-widow peaked mom ? • Genotype for mom= ww • Genotype for dad = Ww • What are the offspring possibilities between a hybrid widow peaked dad and a non-widow peaked mom ? W w w W w ww w Ww w w Probability of Ww offspring (Widow’s Peak) = 2 out of 4 or 50% Probability of WW offspring (Widow’s Peak) = 0 out of 4 or 0% Probability of ww offspring (no Widow’s Peak) = 2 out of 4 or 50 % Monohybrid Punnett Squares • A monohybrid cross is exploring the possibilities of only one trait. For example, what will the offspring look like when a hybrid green and yellow podded plant are crossed. You are ONLY looking at one trait- pod color. • Green X Yellow • Green alleles = G or g • Yellow alleles = g G g g G g g g g Gg g g Dihybrid Punnett Squares • A dihybrid cross is exploring the possibilities of TWO traits. For example, what will the offspring look like when a hybrid yellow, wrinkled pea plant is crossed with a green, hybrid round pea plant. You are looking at two traits- pea color and pea texture. • Yellow, Wrinkled = Yyrr • Green, Round = yyRr Dihybrid Punnett Squares • For a dihybrid cross, you must think of all of the possible combination of alleles. • For example, a yellow wrinkled plant (Yyrr) can offer the possible allele combinations: Yr, yr. What are the possible allele combinations for a green, smooth wrinkled plant (yyRr)? yR, yr Dihybrid Punnett Squares • What are the possible allele combinations for a yellow, smooth plant (YyRr)? YR, Yr, yR, yr • What are the possible allele combinations for a green, wrinkled plant (yyrr)? yr Yellow, wrinkled (Yyrr) x Green, Round (yyRr) Yr Y r yr y R Yy Rr Y y Rr y y R r y r Yy rr Y y r r y y r r R y y Rr R Y y Y r y R r y yr y yR r y yr r y yR r r r r y r r y y r y Y Y y y r r y r Test Cross • A test cross is used to determine the genotype of an unknown organism. For example, you have a tall pea plant but you do not known if it is homozygous (TT) or heterozygous (Tt). To determine this, you test cross the plant with a homozygous recessive plant- or a SHORT plant. If the unknown is Tt, you will have some short offspring, if it is TT, you will have all tall offspring. Tall plant (TT or Tt) x short plant (tt)