Introduction to Genetics and Mendelian Laws

A set of practice flashcards covering basic genetics, Mendelian laws, Punnett squares, and human inheritance patterns based on lecture notes.

What is the definition of genetics?

Genetics is the study of heredity.

Who was Gregor Mendel ($1822-1884$)?

An Austrian monk and contemporary of Charles Darwin who developed the modern idea of how traits were inherited through carefully designed experiments with pea plants.

What was the common assumption about sexual reproduction before Mendel's work?

The assumption was that sexual reproduction resulted in a blending of traits, such as red and white flowers producing pink flowers.

What is an allele?

Alleles are alternative forms of genes.

How are dominant and recessive alleles distinguished in writing?

Dominant alleles are always in CAPITAL letters, while recessive alleles are always in lower-case letters.

Define the terms homozygous and heterozygous.

A genotype is homozygous if it is made up of $2$ identical alleles ($PP$ or $pp$) and heterozygous if it is made up of $2$ different alleles ($Pp$).

What is the difference between a genotype and a phenotype?

Genotype refers to the genetic makeup or allelic combination (e.g., $PP$, $Pp$, or $pp$), while phenotype refers to the outward appearance (e.g., purple or white flower color).

What is a monohybrid cross?

A cross breeding experiment that examines only one trait resulting from the cross.

In Mendel's monohybrid cross of flower color ($Pp \times Pp$), what was the resulting phenotypic ratio in the $F_2$ generation?

$3$ purple : $1$ white.

In Mendel's monohybrid cross of flower color ($Pp \times Pp$), what was the resulting genotypic ratio in the $F_2$ generation?

$1\,PP : 2\,Pp : 1\,pp$.

State Mendel's Law of Segregation.

Each organism contains two factors (alleles) for each trait, and these factors segregate during the formation of gametes so that each gamete contains only one factor for that trait.

What is a dihybrid cross?

A cross that follows the inheritance of two different traits, such as seed shape and seed color.

State Mendel's Law of Independent Assortment.

Members of one pair of factors separate (assort) independently of members of another pair of factors, allowing all possible combinations of factors to occur in the gametes.

What is the phenotypic ratio of a dihybrid cross between two heterozygotes ($BbNn \times BbNn$)?

$9:3:3:1$.

What is a testcross used for?

A testcross is performed to determine the unknown genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive ($bb$) individual.

Which mathematical rules are used to determine the probability of genetic events?

The rule of multiplication and the rule of addition.

List three examples of dominant human traits from the transcript.

Freckles, Widow's peak, and Free earlobes.

List three examples of recessive human traits from the transcript.

No freckles, Straight hairline, and Attached earlobe.

According to the eye color data, what percentage of the world population has brown eyes?

$70-79\%$.

Which eye colors are listed as having the lowest percentage ($1\%$) worldwide?

Red/Violet and Heterochromia.

In a pedigree chart, what do the square and circle symbols represent?

A square represents a male and a circle represents a female.

In a pedigree chart, what does a shaded symbol indicate?

An affected individual.