Genetics 2

A complete deck of vocabulary flashcards covering key concepts from Genetics 2 and 3 lectures, including cell division, Mendelian laws, non-Mendelian inheritance modes, sex-inherited traits, and epistasis.

Alleles

Different forms of the same gene located at a specific locus on corresponding homologous chromosomes.

Principle of Segregation

Mendel's law stating that allele pairs separate during gamete formation so that only one randomly chosen allele ends up in a gamete.

Principle of Independent Assortment

Mendel's law stating that the separation of alleles for one gene on nonhomologous chromosomes is independent of the separation of alleles for other genes.

Cell Cycle

The sequence of growth ($G_1$, $S$, $G_2$), nuclear division ($M$), and resting phases ($G_0$) where non-dividing cells execute their specialized functions.

Meiosis

The process of cell division that produces gametes (spermatozoa and oocytes), reducing the chromosome number from diploid to haploid.

Synapsis

The event during Prophase I of meiosis where homologous chromosomes align and wrap tightly around each other.

Crossing Over

The exchange of genetic material between non-sister chromatids of homologous chromosomes during Prophase I, producing recombinant chromatids and promoting genetic variation.

Meiosis I

The first meiotic division, known as a reduction division, in which homologous chromosome pairs separate to convert 1 diploid cell into 2 haploid daughter cells.

Meiosis II

The second meiotic division in which sister chromatids separate without prior DNA replication, resulting in 4 haploid daughter cells from 2 haploid cells.

Dominant Allele

An allele (e.g., $A$) that overpowers a recessive allele and prevents its expression at the corresponding locus on the homologous chromosome pair.

Recessive Allele

An allele (e.g., $a$) whose phenotypic expression is masked by a dominant allele at the corresponding locus.

Incomplete Dominance

A mode of inheritance where an allele is expressed in a dose-dependent manner, producing an intermediate phenotype in heterozygotes (e.g., red $RR$ and white $rr$ roses producing pink $Rr$ offspring).

Codominance

A mode of inheritance in which neither allele masks the other, causing both alleles to be fully expressed simultaneously in heterozygous animals (e.g., roan coat color $R^r R^w$ in cattle).

Sex-Linked Traits

Traits resulting from genes located within non-homologous regions of the X chromosome.

X-Inactivation

The random inactivation or deletion of one of the two X chromosomes in every cell of female mammals during early embryogenesis, resulting in patchwork fur patterns in heterozygous ($X^B X^b$) female cats.

Sex-Limited Traits

Traits whose phenotypic expression is limited to only one sex, despite genes for the trait being carried by both males and females (e.g., milk production in female cattle).

Sex-Influenced Traits

Traits where reciprocal expression occurs between sexes, causing an allele to behave as dominant in one sex and recessive in the other (e.g., horned vs. polled traits in sheep).

Epistasis

A gene interaction in which expression of a gene at one locus masks or modifies the phenotypic expression of a gene at a different locus (e.g., coat color in Labrador retrievers).

Chicken Comb Epistasis

The epistatic gene interaction between Rose ($R$) and Pea ($P$) loci resulting in four distinct comb shapes: walnut ($R\_ P\_$), rose ($R\_ pp$), pea ($rrP\_$), and single ($rrpp$).