How do you use a Punnett Square to perform a genetic cross?

  1. State the phenotypes of the two parents
  2. Assign the genotypes of the parents letter codes (like GG for homozygous dominant, Gg for  heterozygous, and gg for homozygous recessive)
  3. State the gametes of the parents (like G or g)
  4. Use the Punnett square to show all possible results of the random fertilisation of parental gametes
  5. State the proportion of each genotype among the offspring as a ratio or percentage
  6. State the proportion of each phenotype among the offspring

Answer in your head, out loud, or on paper, then tap the card to flip.

What is monohybrid inheritance?

Monohybrid (monogenic) inheritance involves the transmission of a single gene from parents to their offspring.

Answer in your head, out loud, or on paper, then tap the card to flip.

What is the difference between a homozygous organism and a heterozygous organism?

An organism with two identical alleles for a trait is homozygous.


An organism with two different alleles for a trait is heterozygous.

Answer in your head, out loud, or on paper, then tap the card to flip.

What is the difference between a dominant allele and a recessive allele?

A dominant allele is always expressed in the phenotype, even when only one copy is present in the genotype.


A recessive allele is only expressed when it is homozygous in the genotype (two copies are present), and is masked by a dominant allele.

Answer in your head, out loud, or on paper, then tap the card to flip.

What is a locus?

A locus (plural: loci) is the specific position of a gene on a chromosome.

Answer in your head, out loud, or on paper, then tap the card to flip.

What are alleles?

Alleles are different versions of genes that code for variants of a characteristic.

Answer in your head, out loud, or on paper, then tap the card to flip.

What is a gene?

A gene is a sequence of bases on a DNA molecule that codes for a protein (polypeptide).

Answer in your head, out loud, or on paper, then tap the card to flip.

What is the difference between a genotype and a phenotype?

A genotype is the genetic makeup for a trait, describing the alleles that an organism has.


A phenotype is the physical characteristic that the genotype produces in interaction with the environment.

Answer in your head, out loud, or on paper, then tap the card to flip.

What is the F1 generation in genetic crosses?

The F1 generation consists of offspring from a cross between individuals with homozygous dominant and homozygous recessive genotypes.


All the offspring will be heterozygous, inheriting a recessive allele from one parent and a dominant allele from the other parent.


They will therefore all express the dominant trait in their phenotype.

Answer in your head, out loud, or on paper, then tap the card to flip.

What is the F2 generation?

The F2 generation results from a cross between two F1 individuals, exhibiting a 3:1 ratio of dominant to recessive phenotypes.

Answer in your head, out loud, or on paper, then tap the card to flip.

What is a test cross?

A test cross involves breeding an organism with a dominant phenotype and an unknown genotype with an organism that is homozygous recessive.


This allows us to determine the parent's unknown genotype.

Answer in your head, out loud, or on paper, then tap the card to flip.