AP Lecture Ch 4

Gene

An information-containing segment of DNA that codes for the production of a molecule of RNA that plays a role in synthesizing one or more proteins.

DNA Structure

DNA consists of two strands forming a double helix, with a backbone composed of alternating phosphate groups and deoxyribose sugar.

Nucleotide

The basic building block of DNA, consisting of one sugar (deoxyribose), one phosphate group, and one nitrogenous base.

Purines

A class of nitrogenous bases in DNA with a double ring structure; include adenine (A) and guanine (G).

Pyrimidines

A class of nitrogenous bases in DNA with a single ring structure; include cytosine (C) and thymine (T).

Chromatin

Fine filamentous DNA material complexed with proteins, which occurs as long filaments called chromosomes.

Genome

All the genes of one person, estimated to be between 20,000 to 25,000 genes in humans.

Heredity

The transmission of genetic characteristics from parent to offspring.

Mitosis

Cell division in all body cells except the eggs and sperm, involved in growth, cell replacement, and tissue repair.

Alleles

Different forms of a gene at the same locus on two homologous chromosomes.

Phenotype

An observable trait manifested from the expression of alleles.

Genotype

The alleles that an individual possesses for a specific trait.

Carcinogen

Environmental cancer-causing agents, which may include radiation, chemicals, or viruses.

Oncogenes

Genes that cause cell division to accelerate uncontrollably and stimulate mitosis.

Tumor-suppressor genes

Genes that inhibit the development of cancer by opposing the action of oncogenes.

Penetrance

The percentage of a population with a given genotype that actually exhibits the predicted phenotype.

Semiconservative replication

A process of DNA replication where each daughter DNA molecule consists of one new and one old helix.

Gene Regulation

The mechanism by which genes are turned on and off based on the needs of the cell.

Codominance

A genetic scenario where both alleles in a heterozygote are fully expressed.

Incomplete dominance

A genetic scenario where the phenotype is a blend of both alleles.

Diploid

Any cell with 23 pairs of chromosomes, typical of somatic cells.

Haploid

Cells that contain half as many chromosomes as somatic cells, such as sperm and egg cells.