Single-Gene Inheritance and Genetic Analysis

Comprehensive vocabulary flashcards generated from lecture notes covering genetics fundamentals, forward and reverse genetics, Mendelian inheritance, and molecular allele characteristics.

Forward genetics

The classical approach to genetic analysis, in which genes are first identified by mutant alleles and mutant phenotypes and later cloned and subjected to molecular analysis.

Gene discovery

The process whereby geneticists find a set of genes affecting some biological process of interest by the single-gene inheritance patterns of their mutant alleles or by genomic analysis.

Wild type

The genotype or phenotype that is found in nature or in the standard laboratory stock for a given organism.

Mutant

An organism or cell carrying a mutation.

Reverse genetics

An experimental procedure that begins with a cloned segment of DNA or a protein sequence and uses it (through directed mutagenesis) to introduce programmed mutations back into the genome to investigate function.

William Bateson

First Director of the John Innes Institute and Cambridge professor who coined the term "genetics".

Pisum sativum

The garden pea; a dicot plant, self-fertile, naturally inbred and true-breeding model organism used by Gregor Johann Mendel.

Seven phenotypic pairs studied by Mendel

The contrasting phenotypes studied in Pisum sativum: round or wrinkled ripe seeds, yellow or green seeds, purple or white petals, inflated or pinched ripe pods, green or yellow unripe pods, axial or terminal flowers, and long or short stems.

Law of Segregation (First Law)

Mendelian principle stating that during gamete formation, paired unit factors (alleles) separate (segregate) randomly.

Monohybrid cross

A genetic cross involving single genes, such as the segregation of yellow vs. green peas.

Locus

The specific place on a chromosome where a gene is located.

Haplosufficient

Describing a gene where a single functional allele is able to produce the wild-type phenotype with only one copy.

Haploinsufficient

Describing a gene where a single functional allele is unable to produce the wild-type phenotype with only one copy and therefore is masked or results in an abnormal state.

Null allele

An allele whose effect is the absence either of normal gene product at the molecular level or of normal function at the phenotypic level.

Genetic trait

The outward manifestation of gene function, such as seed color.

Filial ($F_1$, $F_2$, or $F_X$)

First, second, or $X$ generation offspring from a cross.

Homozygous

Having two identical alleles for a given gene.

Heterozygous

Having two different alleles for a given gene.

Dominant trait

A trait that is expressed in a heterozygote.

Recessive trait

A trait that is masked in a heterozygote.

Alleles

Different forms of the same gene or a version of a gene arising from a difference in DNA sequence.

Phenotype

Physical appearance or observable expression of an organism.

Genotype

Actual genetic make-up (the genetic constitution) of an organism.

Segregation

Variation among individuals for a trait due to the separation of allele pairs during gamete formation.

True-breeding

Refers to organisms where selfing of an individual always results in offspring with the same phenotype as the parent (no segregation).

Genetic mutation

A change in DNA sequence of a gene, sometimes resulting in the loss of that gene's function.

Test cross

A cross used to determine the identity of a dominant phenotype of unknown genotype by crossing it with a homozygous recessive individual.

Principle of $F_1$ uniformity

The observation that all $F_1$ progeny from crosses of true-breeding lines resemble one of the parents.