Mendel Punnett squares notes

Who was Gregor Mendel?

Gregor Mendel is known as the father of genetics for his foundational work on heredity using pea plants.

What is a Punnett square?

A Punnett square is a diagram used to predict the outcome of a genetic cross by showing the possible allele combinations.

True or false: Punnett squares can show phenotypes.

True, because they can illustrate the expected observable traits from genotypes.

Difference between genotype and phenotype.

Genotype refers to the genetic makeup (alleles), while phenotype is the physical expression of those genes.

What does homozygous mean?

Homozygous means having two identical alleles for a particular gene, like AA or aa.

Fill in the blank: A Punnett square's axes represent ___.

the gametes of the parents involved in the genetic cross.

What does heterozygous mean?

Heterozygous means having two different alleles for a particular gene, such as Aa.

True or false: Punnett squares can predict exact outcomes.

False, because they provide probabilities, not certainties.

Possible genotypes from Aa x Aa cross.

AA, Aa, Aa, aa — resulting in a 1:2:1 ratio.

Question: What ratio results from Aa x aa?

1:1 — Offspring will either be Aa or aa.

What is Mendelian inheritance?

Mendelian inheritance describes how traits are passed from parents to offspring through alleles.

Which allele is dominant, A or a?

A is dominant over a, meaning it masks the effect of the recessive allele.

Application: Predict the offspring of BB x Bb.

Possible genotypes: BB, BB, Bb, Bb — a 3:1 ratio of dominant to recessive phenotypes.

Question: What is the phenotypic ratio of AaBb x AaBb?

9:3:3:1 in a dihybrid cross.

Which generation is P generation?

The parental generation; it is the initial cross of true-breeding plants.

Fill in the blank: F1 generation results from ___.

the cross of two P generation individuals.

True or false: Alleles can be identical in F1 generation.

False, F1 typically has heterozygous alleles from dominant and recessive parents.

What is a test cross?

A test cross is used to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive.

Difference between monohybrid and dihybrid cross.

Monohybrid involves one trait, while dihybrid involves two traits.

Question: What is the expected ratio of traits in a monohybrid cross?

The expected ratio is 3:1 for dominant to recessive traits.

What does the term 'allele' mean?

An allele is a variant form of a gene that can produce different traits.

Explain the law of segregation.

The law of segregation states that allele pairs separate during gamete formation.

Question: What is a phenotype?

A phenotype is the observable characteristics resulting from the genotype.

What does it mean if a trait is recessive?

A recessive trait only expresses itself when two copies of the allele are present.