Genetic Control of Cell Function & Inheritance CH. 4

Vocabulary flashcards covering fundamental genetics, DNA replication, protein synthesis, mutations, chromosomal structure, and inheritance principles.

Gene

The basic unit of heredity, located on chromosomes, that codes a specific nucleotide sequence in DNA and encodes proteins.

Genetics

The study of biologic heredity.

Genome

The DNA of ALL the genes for a given species; the human genome contains approximately 20,000 to 25,000 genes.

Genomics

The field of genetics that addresses both the structural and functional studies of the genome.

DNA (Deoxyribonucleic Acid)

A double helix molecule composed of pentose sugar (deoxyribose), phosphate groups, and nitrogenous base pairs (A-T and C-G) that provides the code for body proteins.

Codon

A sequence of three nitrogenous bases (triplet) in genetic code that specifies a single amino acid or signals termination of protein production.

Replication

The process by which a cell unwinds its DNA double helix using helicase and uses DNA polymerase to build complementary strands, producing an exact copy of its DNA before cell division.

Helicase

The enzyme that unzips the DNA double helix during replication by separating the two strands.

DNA Polymerase

The enzyme that brings in free nucleotides and matches them to complementary bases on the original DNA strand during replication.

Transcription

The process by which a cell uses RNA polymerase to copy a specific gene from DNA into messenger RNA (mRNA) in the nucleus.

Translation

The process in which ribosomes read mRNA codons in the cytoplasm and tRNA delivers matching amino acids to build a growing polypeptide chain.

Transfer RNA (tRNA)

RNA that carries specific amino acids to the ribosome and pairs its anticodon with the complementary mRNA codon during translation.

Mutation

A change in the DNA sequence that alters the genetic instructions for making a protein.

Base Pair Substitution

A point mutation where one base pair is replaced by another, which may change a single amino acid or have no effect.

Mutagens

Agents, such as radiation and chemicals, that increase the frequency of mutations.

Somatic Cells

Diploid body cells containing 46 chromosomes (23 pairs), with one set inherited from the mother and one set from the father.

Gametes

Haploid reproductive cells (sperm and egg cells) containing 23 chromosomes.

Meiosis

The process of cell division resulting in the formation of haploid cells from diploid cells.

Autosomes

The first 22 of the 23 pairs of chromosomes in males and females, which are virtually identical and homologous.

Sex Chromosomes

The 23rd pair of chromosomes that determines sex, being homologous (XX) in females and nonhomologous (XY) in males.

Chromosomal Deletion

A structural chromosome alteration resulting from broken chromosomes and loss of DNA.

Chromosomal Duplication

A rare structural chromosome alteration featuring a repeated gene or gene sequence.

Chromosomal Inversion

A structural chromosome alteration where a chromosome segment is reversed end-to-end.

Chromosomal Translocation

The transfer of a chromosome segment from one chromosome to another.

Fragile Sites

Areas on chromosomes that develop distinctive breaks or gaps, which are associated with folate deficiency.

Mendelian Traits

Inherited traits that are primarily attributed to single genes.

Locus

The specific location occupied by a gene on a chromosome.

Allele

One of several different forms of a gene at a given locus.

Homozygous

Having two identical alleles at a specific gene locus.

Heterozygous

Having two different alleles at a specific gene locus.

Polymorphism

A gene locus that has two or more alleles occurring with appreciable frequency in a population.

Genotype

The composition of genes at a given locus; the genetic code of an individual.

Phenotype

The outward appearance or clinical expression of an individual, resulting from the interaction of genotype and environment.

Codominant Alleles

Alleles that are both expressed in the phenotype when present together in a heterozygote.

Carrier

An individual who possesses a disease-causing allele but is phenotypically normal and does not express the disease.

Pedigree

A specialized family chart used to study the transmission of specific genetic traits across generations.

Proband

The first person in a family diagnosed with a genetic disorder or seen in a clinic (propositus for a male, proposita for a female).

Principle of Segregation

Mendel's law stating that homologous genes separate from one another so that each gamete carries only one gene of each pair.

Principle of Independent Assortment

Mendel's law stating that the hereditary transmission of one gene does not affect the transmission of another gene.

Penetrance

The percentage of individuals with a specific genotype who express the expected phenotype.

Incomplete Penetrance

A situation where an individual possesses the gene for a disease but does not express the clinical disease (e.g., retinoblastoma).

Age-dependent Penetrance

A phenomenon where an individual does not express a genetic disease until reaching a certain age (e.g., Huntington's disease).

Expressivity

The degree of variation in phenotype associated with a particular genotype (e.g., von Recklinghausen disease).