Gene Expression and Genetics

Vocabulary terms and definitions from lecture notes covering genomic structure, transcription, translation, mutations, and inheritance patterns.

Introns

Segments of DNA that are not involved in coding for a protein; they must be removed before translation can occur.

Exons

The remaining segments of DNA that are spliced together to form the strand of mRNA that leaves the nucleus.

Transcription

The process occurring in the nucleus where a specific gene is transcribed from DNA into a single strand of messenger RNA (mRNA).

Promoter

A sequence of DNA that occurs at the beginning of a gene where RNA polymerase finds and unzips the DNA.

RNA polymerase

The enzyme that finds the promoter, unzips the DNA, and transcribes the gene into mRNA until it reaches the terminator sequence.

Silent mutation

A type of base substitution mutation where there is no change to the amino acid. letter is changed but codes for the same amino acid

Missense mutation

A type of base substitution mutation that results in one amino acid change.

Nonsense mutation

A type of base substitution mutation where an amino acid is changed to a stop codon.

Frameshift mutation

A mutation caused by the insertion or deletion of a letter in the DNA sequence.

Ribosome

The cellular structure that carries out translation by reading mRNA letters in sequences of three.

Codon

A three-letter sequence of mRNA that corresponds to one of twenty amino acids.

Transfer RNA (tRNA)

The molecule that carries the appropriate amino acid to the ribosome as the mRNA strand is translated.

Translation

The process by which a strand of mRNA is converted into a protein.

Deoxyribonucleic acid (DNA)

The genetic material found in the nucleus of almost all somatic cells, featuring a double helix structure.

Nitrogenous bases

The four chemical components of DNA: Adenine, Thymine, Guanine, and Cytosine.

X-linked traits

Genes carried on the X chromosome; examples include fur color in cats where black is $X^B$ and orange is $X^b$.

ZW inheritance model

The method of sex determination in birds, snakes, and butterflies where $ZZ$ is male and $ZW$ is female.

Haplodiploidy

males deduce unfertilized eggs and only females produce fertilized eggs. The method of sex determination used by honeybees.

Incomplete dominance

Occurs when a heterozygous individual has a phenotype intermediate between homozygous individuals, such as in snapdragon flowers.

Codominance

Occurs when multiple dominant alleles are equally expressed together, such as in Human ABO blood type.

Polygenic

Describes phenotypes, like human eye color, that are determined by the involvement of multiple genes.

Pleiotropy

A phenomenon where one gene controls multiple phenotypes, such as Marfan syndrome.

Autosomal traits

Traits found on chromosomes other than the sex chromosomes.

Testcross

A procedure involving crossing a dominant phenotype with a recessive phenotype to determine the genotype of the dominant organism.

Phenotype

The physically expressed trait of an organism.

Genotype

The genetic makeup of an organism.

Heterozygous

The condition of having two different alleles for a specific gene (e.g., $Pp$).

Punnett square

A tool that shows all possible offspring that can result from a union of two parents.

Alleles

Alternative versions of a gene.

Homozygous

The condition of having two identical alleles for a particular gene.

Diploid

Refers to organisms or cells that have two copies of each gene.

Gregor Mendel

An Austrian monk who experimented with pea plants in the mid-1800s to explain how traits are inherited.

Gene

A segment of DNA that codes for a particular trait.

Genetics

The study of inheritance.

Blending concept

A historical concept used to explain inheritance before modern genetics.