Genetics: Alleles and Punnett Squares

The video tutorial covers monohybrid crosses, focusing on key genetic vocabulary such as homozygous, heterozygous, dominant, and recessive traits. It explains genotype and phenotype with examples, using 'N' for nose size. An example problem involving the freckles trait is solved using a Punnett square, demonstrating how to determine the probability of offspring traits. The tutorial emphasizes that the recessive phenotype only appears with a homozygous recessive genotype.

What is the term for an organism with two identical alleles for a trait?

• Recessive

• Heterozygous

• Homozygous

• Dominant

In the example of nose size, what does a genotype of 'Big N Big N' represent?

• Medium nose

• Large nose

• Small nose

• No nose

What is the phenotype of an organism with a genotype of 'small n small n'?

• Large nose

• Small nose

• Medium nose

• No nose

Which genotype is necessary to express a recessive trait?

• Homozygous dominant

• Heterozygous

• Homozygous recessive

• Dominant

In the freckles example, what is the genotype of a heterozygous individual?

• Big F Big F

• Big F Big N

• Big F small f

• small f small f

What does a Punnett square help determine?

• The size of an organism

• The probability of genotypes

• The age of an organism

• The color of an organism

What is the probability of having a child with freckles if one parent is heterozygous and the other is homozygous dominant?

• 75%

• 25%

• 50%

• 0%

In a Punnett square, which genotype represents no freckles?

• small f small f

• Big F Big N

• Big F small f

• Big F Big F

Why is it important to write the dominant allele first in a genotype?

• It shows dominance

• It's easier to read

• It's a rule of thumb

• It looks better

What is the phenotype of an organism with a genotype of 'Big F small f' in the freckles example?

• Partial freckles

• Unknown

• No freckles

• Freckles