Genetics Flashcards

The two alleles for each gene separate during gamete formation so each gamete carries only one allele.

Genes on different chromosomes are inherited independently because homologous pairs orient randomly during meiosis I.

3:1 dominant to recessive (genotypic ratio 1 AA : 2 Aa : 1 aa).

Both alleles are fully expressed in the heterozygote (e.g., AB blood type expresses both A and B antigens).

The heterozygous phenotype is intermediate between the two homozygotes (e.g., red x white snapdragons produce pink).

Crossing a dominant-phenotype individual with a homozygous recessive to determine if the dominant parent is homozygous or heterozygous.

Each parent strand serves as a template, so each daughter molecule has one original strand and one new strand.

Unwinds the double helix by breaking hydrogen bonds at the replication fork, creating single-stranded templates.

DNA polymerase cannot initiate a new strand; it needs a free 3'-OH group provided by a short RNA primer laid down by primase.

The leading strand is synthesized continuously toward the fork; the lagging strand is synthesized in short Okazaki fragments away from it.

RNA polymerase synthesizes mRNA from a DNA template. In eukaryotes it occurs in the nucleus.

5' methylguanosine cap, 3' poly-A tail, and RNA splicing (introns removed, exons joined by the spliceosome).

Ribosomes synthesize a polypeptide from mRNA in the cytoplasm; tRNA delivers amino acids matched to codons via anticodons.

A three-nucleotide mRNA sequence encoding one amino acid or a stop signal. 64 codons encode 20 amino acids plus 3 stops (redundant code).

Silent (no amino acid change), missense (different amino acid), and nonsense (premature stop codon).

One gene's expression masks or modifies another gene at a different locus (e.g., coat color in Labrador retrievers).

Males have only one X chromosome, so a single recessive allele is expressed. Females need two copies to show the trait.

A trait controlled by two or more genes with additive effects, producing continuous variation (e.g., height, skin color).

DNA is transcribed to RNA, which is translated to protein (DNA -> RNA -> Protein).

An insertion or deletion (not a multiple of three) that shifts the reading frame, altering all downstream amino acids and usually producing a nonfunctional protein.

Genotype is the allele combination an organism carries (e.g., Bb); phenotype is the observable trait expressed, influenced by genotype and environment.

A diagram that predicts offspring genotypic and phenotypic ratios by combining one allele from each parent per grid box.

When lactose is absent, a repressor blocks transcription. When present, allolactose binds the repressor, releasing it so RNA polymerase transcribes the genes.

Genes close together on the same chromosome that tend to be inherited together; crossing over can separate them at a rate proportional to their distance.

Allele frequencies stay constant when there is no selection, mutation, gene flow, or genetic drift, and mating is random.