Genetics | Dihybrid Crosses (Example 1)

The video tutorial explains dihybrid crosses, building on the concept of Punnett squares and monohybrid crosses. It covers the setup of dihybrid crosses, calculation of possible genotypes and phenotypes, and determination of genotypic and phenotypic ratios. The tutorial emphasizes understanding genetic inheritance and the complexity of dealing with two genes simultaneously.

What is the primary purpose of using a Punnett square in genetics?

• To determine the age of an organism

• To calculate the speed of genetic mutations

• To identify the number of chromosomes in a cell

• To predict the possible genotypes and phenotypes of offspring

In a monohybrid cross, how many copies of each gene does a human have?

• Two

• One

• Four

• Three

What is the difference between monohybrid and dihybrid crosses?

• Monohybrid crosses are simpler than dihybrid crosses

• Monohybrid crosses involve two genes, dihybrid crosses involve one

• Monohybrid crosses are used for plants, dihybrid crosses for animals

• Monohybrid crosses involve one gene, dihybrid crosses involve two

When setting up a dihybrid cross, how many possible combinations of alleles are there for each parent?

• Two

• Four

• Eight

• Sixteen

What is the genotype of an offspring with homozygous dominant height and heterozygous speed?

• Big A big A, little b little b

• Big A little a, big B big B

• Big A big A, big B little b

• Little a little a, big B little b

How many cells are there in a dihybrid cross Punnett square?

• Four

• Sixteen

• Eight

• Twelve

What is the phenotypic ratio for a dihybrid cross with eight tall and fast, and eight tall and slow offspring?

• 4:1

• 3:1

• 2:1

• 1:1

Which of the following is a possible genotypic ratio in a dihybrid cross?

• 3:1

• 1:2:1

• 9:3:3:1

• 2:2

What does a homozygous recessive genotype for speed indicate in terms of phenotype?

• Fast

• Slow

• Medium

• Variable

What should you do if your teacher asks for the empirical ratio of genotypes?

• Multiply all numbers by 2

• Add all numbers together

• Divide all numbers by the smallest number

• Reduce the ratio to its simplest form