Mendel and the Gene Idea / Chromosomal Basis of Inheritance - Vocabulary Flashcards

Vocabulary flashcards covering key Mendelian genetics and chromosomal inheritance concepts from the notes.

Blending hypothesis

The idea that genetic material from two parents blends in offspring (like blue and yellow making green); largely replaced by the particulate view.

Particulate hypothesis

The idea that parents pass discrete heritable units (genes) that retain their identity in offspring.

Gene

A basic unit of heredity that governs a specific trait.

Allele

One of two or more alternative versions of a gene at a given locus.

Locus

A specific location on a chromosome where a gene is found.

True-breeding

Organisms that produce offspring of the same variety when self-pollinated.

P generation

Parental generation in a genetic cross.

F1 generation

First filial generation; offspring of the P generation.

F2 generation

Second filial generation; offspring of the F1 generation.

Hybridization

Mating of two contrasting true-breeding varieties.

Dominant allele

An allele that determines the phenotype when present with a recessive allele.

Recessive allele

An allele that has no noticeable effect on phenotype when paired with a dominant allele.

Phenotype

The physical appearance or observable traits of an organism.

Genotype

The genetic makeup of an organism; the alleles present at a locus.

Homozygous

Having two identical alleles for a gene.

Heterozygous

Having two different alleles for a gene.

Monohybrid cross

Cross examining the inheritance of a single characteristic.

Dihybrid cross

Cross examining two different characteristics simultaneously.

Law of Segregation

The two alleles for a gene segregate (separate) during gamete formation.

Punnett square

A grid used to predict the genetic outcomes of a cross.

Complete dominance

Heterozygotes and dominant homozygotes have the same phenotype.

Incomplete dominance

The heterozygote phenotype is intermediate between the two parental phenotypes.

Codominance

Two dominant alleles affect the phenotype in separate, distinguishable ways.

Multiple alleles

More than two allelic forms of a gene exist in the population (e.g., ABO blood groups).

Pleiotropy

One gene influencing multiple, seemingly unrelated phenotypic traits.

Epistasis

A gene at one locus alters the expression of a gene at a second locus.

Polygenic inheritance

A trait controlled by two or more genes; often results in a continuum of phenotypes (quantitative).

Quantitative trait

A trait that varies continuously across a population (often Polygenic).

Multifactorial

Traits influenced by both genetic and environmental factors.

Pedigree

A family tree used to study the inheritance of traits across generations.

Sex-linked gene

A gene located on a sex chromosome (X-linked or Y-linked).

X-linked gene

A gene located on the X chromosome.

Y-linked gene

A gene located on the Y chromosome.

Hemizygous

Males have only one allele for a given X-linked gene (one copy on the X chromosome).

Barr body

The condensed, inactivated X chromosome in female mammals.

X inactivation

Random inactivation of one of the two X chromosomes in female embryonic cells.

Linked genes

Genes located on the same chromosome that tend to be inherited together.

Recombination

Production of offspring with combinations of traits different from the parents, due to crossing over and independent assortment.

Crossing over

The exchange of chromosome segments between homologous chromosomes during meiosis.

Recombination frequency

The percentage of offspring with recombinant phenotypes; used to map gene distance.

Linkage map

A genetic map based on recombination frequencies showing the order of genes on a chromosome.

Map unit

A unit representing a 1% recombination frequency on a linkage map.

Morgan

Thomas Hunt Morgan, founder of chromosome theory of inheritance using Drosophila (fruit flies).

Wild type

The most common phenotype in nature for a given character.

Mutant phenotype

An alternative phenotype that differs from the wild type.

Nondisjunction

Failure of chromosome separation during meiosis, leading to abnormal chromosome numbers.

Aneuploidy

Abnormal number of chromosomes in a cell.

Monosomy

One copy of a particular chromosome (loss of one chromosome copy).

Trisomy

Three copies of a particular chromosome.

Polyploidy

More than two complete sets of chromosomes in an organism.

Deletion

Loss of a chromosomal segment.

Duplication

Replication of a chromosomal segment.

Inversion

Reversal of a chromosome segment.

Translocation

Movement of a chromosome segment to a nonhomologous chromosome.

Cri du chat

A syndrome caused by a deletion on chromosome 5.

Philadelphia chromosome

A translocation between chromosomes 9 and 22 associated with CML.

Down syndrome

Trisomy 21; an extra copy of chromosome 21.

Turner syndrome

Monosomy X (XO) in females; infertile but viable.

Klinefelter syndrome

XXY karyotype in males; typically infertile or with minor features.

XXX syndrome

Triple X syndrome; females with an extra X chromosome.

XYY syndrome

Males with an extra Y chromosome; often normal intelligence.

Autosomes

Chromosomes that are not sex chromosomes.

Chromosome theory of inheritance

Mendelian genes have a specific locus on chromosomes; chromosome behavior explains inheritance laws.

Homozygous vs heterozygous (revisited)

Homozygous: two identical alleles; heterozygous: two different alleles.

Testcross

Breeding a dominant-phenotype individual with a homozygous recessive to determine genotype.