Allele Interactions, Gene Interactions, Gene Linkage, Recombination and Eukaryotic Gene Expression

Vocabulary flashcards from lecture notes.

Complete Dominance

F1 hybrids (heterozygous) resemble one of the true-breeding parents. In complete dominance, the dominant allele completely masks the effect of the recessive allele in a heterozygous genotype. 3:1 F2 ratio

Incomplete Dominance

F1 hybrids have an intermediate phenotype of the parents. 1:2:1 F2 ratio

Codominance

F1 hybrids display traits from both pure-breeding parents. 1:2:1 ratio

Monomorphic gene

A gene with only one wild-type allele.

Pleiotropy

One gene may contribute to several distinct traits.

Additive gene interaction

Two genes can interact to affect a single trait.

Epistasis

One gene can mask the effects of another gene.

Epistatic gene

Gene that masks/hides the effects of another gene.

Hypostatic gene

Gene that is being masked or hidden.

Recessive Epistasis

Coat color in Labrador retrievers is determined by two genes; two independently assorting genes (E and B) control three coat colors: brown, yellow, and black.

Reciprocal recessive epistasis

Sweet pea flower color; At least 1 dominant allele of each gene is necessary for purple color; aa is epistatic to B, bb is epistatic to A.

Dominant epistasis

Summer squash color; dominant allele of one gene masks both alleles of another gene; The dominant B allele causes white color and masks any combination of A and a alleles.

Reciprocal dominant epistasis

Maize leaf development; Redundant gene action result in the 15:1 phenotypic ratio. Dominant A is epistatic to bb; Dominant B is epistatic to aa.

Heterogeneous traits

Have the same phenotype but are caused by mutations in different genes.

Genetic linkage

Genes reside on the same chromosome (linked genes) vs. unlinked genes (on different chromosomes).

Parental class

The combinations originally present in the P generation that show up most frequently in the F2 generation.

Recombinant Class

The reshuffles that occur less often.

Chiasmata

The region where the nonsister chromatids are crossing over.

Loci

Singular location on the chromosome.

Locus

Plural.

Chromosomal interference

Occurrence of crossover in one portion of a chromosome interferes with crossover in an adjacent part of the chromosome.

Coefficient of Coincidence

Observed DCO frequency/ expected DCO frequency.

Interference

1 – Coefficient of Coincidence.

Null hypothesis

Observed values are no different from expected values.

Gene expression

The flow of genetic information from DNA via RNA to protein.

Promoter

DNA sequences that provide the signal to RNA polymerase for starting transcription (located upstream of wherever transcription is starting).

TATA box

Most common RNA polymerase II (poly II) promoter.

Enhancer

Regulatory site that binds to transcription factors.

Transcription factors

Sequence-specific DNA binding proteins that influence transcription.

Exons

Nucleotide sequences that code for amino acids.

Introns

Nucleotide sequences that are transcribed but do not code for amino acids.

Slicing

Removal of introns in eukaryotic mRNA to join exons together.

Splice donor

5’ end of intron (GU exon) 5’ splice site.

Branch site

Within the intron (has to contain at least one A).

Splice acceptor

3’ end of intron (AG exon) 3’ splice site.

Spliceosome

Catalyzes splicing; recognizes specific nucleotides at the 5’ (GU) and 3’ (AG) ends of intros and joins exons together on primary transcripts.

Alternate splicing

Produces different mRNAs from the same primary transcript.

Monocistronic

Directing the synthesis of just one polypeptide.

tRNA

Transfer RNAs mediate the translation of mRNA codons to amino acids.

Ribosomes

Facilitate polypeptide synthesis.