Chromosome Theory of Inheritance – Key Vocabulary

Thirty vocabulary flashcards summarizing essential terms and concepts from the lecture on the Chromosome Theory of Inheritance, covering Mendelian laws, sex linkage, genetic linkage, recombination, and key historical figures.

Boveri-Sutton Chromosome Theory of Inheritance

States that genes occupy specific loci on chromosomes and that chromosomes undergo segregation and independent assortment during meiosis.

Gene

A hereditary factor that occupies a specific locus on a chromosome and codes for a particular trait.

Locus (plural: loci)

The fixed physical position of a gene on a chromosome.

Law of Segregation

Mendelian principle that the two alleles for each gene separate during gamete formation.

Law of Independent Assortment

Mendelian principle stating that alleles of genes on non-homologous chromosomes assort independently during meiosis.

Thomas Hunt Morgan

Geneticist who provided experimental proof that genes are carried on chromosomes, using fruit-fly crosses.

Drosophila melanogaster

The fruit fly species widely used as a model organism in genetic research due to its short generation time and four chromosome pairs.

Wild-type phenotype

The most common, normal form of a trait in a natural population; symbolized with a superscript ‘+’ (e.g., w+).

Mutant phenotype

Any alternative form of a trait that differs from the wild type; often caused by allele mutations (e.g., w for white eyes).

Sex-linked gene

A gene located on either sex chromosome (X or Y).

X-linked gene

A gene located on the X chromosome; humans have ~1100 of these genes.

Y-linked gene

A gene located on the Y chromosome; humans have relatively few (~78), mostly involved in sex determination.

SRY gene

A Y-linked gene that triggers development of testes and male sexual characteristics.

Hemizygous

Possessing only one allele for a gene in an otherwise diploid organism; describes X-linked genes in males (XY).

X-linked recessive disorder

A disease caused by a recessive allele on the X chromosome; expressed in males with one copy and females with two copies.

Color blindness

Common X-linked recessive condition causing difficulty in distinguishing certain colors.

Duchenne muscular dystrophy

X-linked recessive disorder characterized by progressive muscle degeneration due to dystrophin gene mutations.

Hemophilia A/B

X-linked recessive bleeding disorders where blood fails to clot properly.

Linked genes

Genes located on the same chromosome that tend to be inherited together because they do not assort independently.

Parental phenotype

Offspring trait combination identical to one of the parents in a genetic cross involving linked genes.

Recombinant phenotype

Offspring showing a new combination of traits different from either parent, produced by crossing-over.

Genetic recombination

Process by which linked genes are reshuffled during meiosis, producing recombinant chromosomes and novel allele combinations.

Recombinant chromosome

A chromosome that carries genes in a combination not found together in either parent due to crossing-over.

Crossing-over

Exchange of corresponding DNA segments between homologous chromosomes during prophase I of meiosis.

Testcross

A genetic cross between an individual with an unknown genotype and a homozygous recessive individual to reveal the unknown genotype.

Recombination frequency

Proportion of recombinant offspring in a cross; used to estimate distance between linked genes on a chromosome.

XX/XY sex determination system

Chromosomal mechanism in which females have two X chromosomes (XX) and males have one X and one Y (XY).

Meiosis

Specialized cell division producing haploid gametes with one set of chromosomes, explaining segregation and independent assortment.

Mitosis

Process of somatic cell division that produces genetically identical diploid daughter cells.

Genetic variation

Diversity in gene combinations within a population; produced by recombination, independent assortment, and random fertilization.