+ Intro to Punnett Squares Mrs. MacWilliams Biology.
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Transcript of + Intro to Punnett Squares Mrs. MacWilliams Biology.
+
Intro to Punnett SquaresMrs. MacWilliamsBiology
+ REVIEW
THE PARENTS CAN ONLY GIVE ONE OF EACH HOMOLOGOUS CHROMOSOME. BUT, THERE ARE 2 DIFFERENT CHROMOSOMES EACH CAN GIVE!
+ Punnett Squares – 7 Steps We will use 7 STEPS to complete punnett squares. Make
sure you complete ALL 7 STEPS for every assignment and test and quiz.
+Step 1List the type of cross (P, F1, F2)
Parental or Purebread P ALWAYS 2 homozygous individuals
First Filial or F1 generation Term used to describe the offspring obtained from
a P generation ALWAYS 2 heterozygous individuals
Second Filial or F2 generations Term used to describe the offspring obtained from
two individuals from the F1 generation Any other combination (hetero x homo)
+Step 2 List the gender of the parent
Symbol represents male
Symbol represents female
+Step 3 List the genotype of the parents
Genotype – the pair of alleles in the cells of an organism.
The actual GENES in the pair
+Step 4 List the phenotype of parents
Phenotype the organisms appearance of the expressed trait.
The Photo of what the organism looks like The Physical traits of what it looks like
+Step 5 Complete the Punnett Square
A grid that uses symbols to show the possible gene combination from a cross.
+Step 6 List Genotypic Ratio of cross
Homozygous Dominant: Heterozygous: Homozygous Recessive
YY: Yy: yy
+Step 7 List Phenotypic Ratio of cross
Dominant: Recessive
Yellow: green
+ Generation Ratios! KNOW THESE!!!!! Parent (P) generationMonohybrid cross: genotype 4:0phenotype 4:0Dihybrid cross: genotype 16:0
phenotype 16:0 First Filial (F1) generation
Monohybrid cross: genotype 1:2:1phenotype 3:1Dihybrid cross: genotype 1:2:2:4:1:2:1:2:1
phenotype 9:3:3:1Trihybrid cross: phenotype 27:9:9:9:3:3:3:1
Symbol represents female
+ Monohybrid Cross A cross that involve ONLY ONE trait
Ex: Seed color
We will now complete a P generation Punnett Square and an F1 generation Punnett Square
+