Mendelian Genetics Overview

A cross between two individuals who are heterozygous for the same gene.

An individual that is heterozygous for a single gene.

A cross between two individuals who are heterozygous for two genes.

An individual who is heterozygous for two genes.

The principle that states that during gamete formation, the alleles for each trait separate independently of each other.

States that each pair of alleles segregates independently of each other pair of alleles during gamete formation.

The probability that two or more independent events will occur together is the product of their individual probabilities.

The probability of either one or the other of two mutually exclusive events occurring is the sum of their individual probabilities.

The ratio of phenotypes in the offspring of a dihybrid cross.

How many phenotypes are expected in the offspring of a dihybrid cross based on the law of independent assortment?

The alleles for genes located close to each other on the same chromosome may be inherited together.

The process of how alleles are distributed into gametes.

The outcome of one event does not affect the outcome of another event.

The events that cannot occur at the same time.

The probability of an event occurring.

The probability of any one of two or more mutually exclusive events occurring is calculated by adding together their individual probabilities. For example, the probability of rolling a 1 or a 2 on a standard die is 1/6 + 1/6 = 1/3.

The offspring of a monohybrid cross are called the F1 generation.

The offspring of the F1 generation are called the F2 generation.

The probability of two independent events occurring is calculated by multiplying their individual probabilities. For example, the probability of flipping a coin twice and getting heads on both flips is 1/2 * 1/2 = 1/4.

A multicharacter cross involves crossing two individuals that differ in more than two traits.

In a dihybrid or multicharacter cross, each character is considered separately, and then the probabilities are multiplied together to calculate the overall probability. For example, the probability of a dihybrid cross (YyRr x YyRr) producing a YYRR offspring is 1/4 (probability of YY) * 1/4 (probability of RR) = 1/16.

The Punnett Square is a visual diagram used to predict the genotypes and phenotypes of the offspring of a cross.

Predictions about the outcome of a cross can be tested experimentally by crossing the individuals and observing the phenotypes of the offspring.

The results of an experiment can be compared to the theoretical predictions based on the rules of probability. For example, if the theoretical phenotypic ratio of a dihybrid cross is 9:3:3:1, then the observed phenotypic ratio should be close to this value.

The probability of a homozygous dominant genotype (YY) in a cross between two heterozygotes (Yy x Yy) is 1/4, or 25%.

The probability of a heterozygous genotype (Yy) in a cross between two heterozygotes (Yy x Yy) is 1/2, or 50%.

The probability of inheriting an allele from a heterozygous parent is 50% or 1/2.

In a dihybrid cross, the probability of getting each homozygous recessive genotype (e.g., aa, bb, cc, dd) is 1/4 (or 1/2 x 1/2).

The probability of obtaining a specific genotype in a tetrahybrid cross is calculated by multiplying the individual probabilities for each gene pair.

For a tetrahybrid cross (AaBbCcDd), the probability of obtaining the genotype aabbccdd is 1/256, as it involves inheriting the recessive allele for all four genes.

A type of gene interaction where one gene's alleles mask or modify the expression of another gene's alleles. This alters the phenotype.

The alleles at one locus (gene location) can affect how the alleles at another locus are expressed.

Coat color in Labrador Retrievers is determined by two genes.

One gene determines the pigment color (B = black, b = brown) while the other gene determines if the pigment is deposited (E = color deposited, e = no color deposited).

A situation where multiple genes contribute to a single trait, resulting in a variety of phenotypes.

Each gene has a small additive effect on the trait, leading to a continuous range of phenotypes.

Traits like height, skin color, and intelligence are controlled by multiple genes.

Polygenic inheritance explains why many human traits are continuous and do not fall into distinct categories.

The phenotype of the heterozygote is a blend of the two homozygous phenotypes.

The phenotype of the heterozygote shows both parental phenotypes distinctly.

The phenotype of the heterozygote is identical to the phenotype of the dominant homozygote.

A single gene can produce multiple phenotypes due to interactions with other genes or the environment.

A gene with more than two alleles in a population. Example: ABO blood group in humans.

The relationship between genotype and phenotype is NOT always simple. Factors like interactions between genes and the environment can influence how genes are expressed.

The alleles for a gene segregate (separate) during gamete formation, so each gamete receives only one allele for each gene.

A single gene can influence multiple phenotypic traits.

The IA allele adds the A carbohydrate, IB allele adds the B carbohydrate, and i allele adds neither.

The multiple alleles for the ABO blood group lead to different combinations of carbohydrates on red blood cells, resulting in the four blood types: A, B, AB, and O.

The ABO blood group system involves three alleles: IA, IB, and i. These alleles determine the type of carbohydrate present on the surface of red blood cells.

The genotype determines the phenotype. For example, individuals with the genotype IAIA or IAi have blood type A, IBIB or IBi have blood type B, IAIB have blood type AB, and ii have blood type O.

Sickle cell anemia is a disease caused by a pleiotropic allele. This allele affects multiple symptoms, including red blood cell shape, oxygen carrying capacity, and susceptibility to infection.

The frequency of certain alleles, like the sickle cell allele, can vary depending on the environment. This is due to the fact that the allele can provide an evolutionary advantage in certain environments, such as regions with malaria.

Some traits are determined by the interaction of two or more genes. These genes can influence each other, leading to complex patterns of inheritance.