ch 2b prbability and pedigrees

This flashcard set covers the vocabulary and principles of transmission inheritance, including Mendel's laws, probability rules, trihybrid crosses, human genetic diseases, and pedigree analysis.

Gene

The region of DNA that codes for a specific product, such as RNA or Protein.

Allele

A version of a gene that codes for the same specific product, though the product is altered in appearance or function.

Mendel’s Law of Independent Assortment

The law stating that during gamete formation, the segregation of alleles at one gene is independent of the segregation of alleles at another gene.

Product Rule

Also called the multiplication rule; it states that the likelihood of two or more independent events occurring simultaneously or consecutively is the product of their individual probabilities.

Sum Rule

Also called the addition rule; it defines the joint probability of occurrence of any two or more mutually exclusive events by summing their individual probabilities.

Forked-line method

A technique for determining gamete genotype frequency where the probabilities of individual alleles are multiplied to determine the probability of each gamete genotype.

Dihybrid Cross F2 Phenotypic Ratio

The characteristic $9:3:3:1$ ratio generated in the second filial generation, illustrating the law of independent assortment.

Nomenclature: $R-$

A notation where the dash indicates that the genotype for round progeny can be either homozygous dominant ($RR$) or heterozygous ($Rr$).

Test cross

A cross between an individual with an unknown genotype (often F1 progeny) and a homozygous recessive individual (e.g., $rrgg$).

Metaphase 1

The stage of the cell cycle to which the random assortment of alleles is related.

Trihybrid Cross

A cross involving three pure-breeding traits, such as Round vs. wrinkled ($RR imes rr$), Yellow vs. green ($GG imes gg$), and Purple vs. white ($PP imes pp$).

Formula for Distinct Phenotypes

The number of distinct phenotypic options is calculated as $(2)^n$, where $n$ is the total number of gene pairs in the cross of one parent.

Formula for Distinct Genotypes

The number of distinct genotypes produced in a cross is calculated as $( ext{genotypes for each gene pair})^n$, such as $3^n$ for a cross between two heterozygotes.

Hemophilia

An X-linked recessive human disease characterized by an inactive blood clotting factor (F8).

Ehlers-Danlos syndrome type IV

An autosomal dominant disorder (COL3A1) characterized by stretchy collagen.

Cystic fibrosis (CFTR)

An autosomal recessive disorder characterized by abnormal chlorine and sodium transport, leading to mucus interference in the lungs.

Sickle-cell anemia (HBB)

An autosomal recessive disorder resulting in a hemoglobin defect that affects red blood cell function.

Pedigrees

Family trees using standard notation (Roman numerals for generations) to trace the inheritance of traits in humans and animals.

Autosomal Dominant Inheritance

Inheritance pattern where males and females are affected equally, the trait usually appears in every generation, and every affected individual has at least one affected parent.

Autosomal Recessive Inheritance

Inheritance pattern where affected individuals are often born to unaffected (heterozygous) parents and the trait may skip generations.

Conditional Probability

A probability applied after a cross has been made when information about the outcome modifies the calculation, such as calculating the chance yellow-seeded progeny are heterozygous.