Chapter 3 — Genetics (3.1–3.5) Vocabulary Flashcards

Vocabulary flashcards covering key genetics concepts from genes and meiosis to inheritance, genetic disorders, and biotechnology.

DNA

The genetic blueprint that codes for and determines an organism's characteristics.

Gene

A sequence of DNA that encodes for a specific trait.

Locus

The position of a gene on a chromosome.

Allele

An alternative form of a gene that codes for variations of a trait; differ by one or a few bases.

Mutation

A change in the nucleotide sequence of DNA coding for a trait.

Beneficial mutation (missense)

A mutation that creates new variation of a trait (missense alteration).

Detrimental mutation (nonsense)

A mutation that truncates the gene sequence by introducing a stop codon.

Neutral mutation (silent)

A mutation that has no effect on the functioning of the feature.

Frameshift mutation

Addition or removal of a base that shifts the reading frame of the gene.

Sickle cell anaemia

A recessive condition caused by a mutation in the beta-globin gene leading to abnormal haemoglobin and sickling.

Genome

The total genetic information of a cell, organism, or organelle.

Human genome

The complete set of human genetic material: 46 chromosomes, about 21,000 genes, ~3 billion base pairs.

Human Genome Project

International effort to sequence and map the human genome, enabling gene mapping, screening, medicine, and ancestry insights.

Chromosome

A structure in which DNA is packaged and organized.

Diploid (2n)

Two sets of chromosomes; two copies of each gene in somatic cells.

Haploid (n)

Half the chromosome number; gametes contain a single set.

Autosome

Chromosomes that are not sex chromosomes.

Sex chromosome

Chromosome that determines sex (X and Y in humans).

Karyotype

The number and types of chromosomes in a eukaryotic cell; a visual profile.

Karyogram

The visual image produced from a karyotype.

Interphase

Stage when DNA is replicated prior to mitosis/meiosis.

Interkinesis

Period between meiosis I and II with no DNA replication.

Meiosis

The process by which sexually produced gametes are formed; a reduction division yielding haploid nuclei.

Prophase I (P I)

Chromosomes condense; nuclear membrane dissolves; homologous chromosomes form bivalents; crossing over occurs.

Metaphase I (M I)

Bivalents align at the equator; spindle fibers attach to them.

Anaphase I (A I)

Homologous chromosomes separate to opposite poles.

Telophase I (T I)

Chromosomes decondense and two haploid cells form.

Prophase II (P II)

Chromosomes condense again in preparation for the second division.

Metaphase II (M II)

Sister chromatids align at the equator.

Anaphase II (A II)

Sister chromatids separate to opposite poles.

Telophase II (T II)

Chromosomes decondense; four haploid cells are produced.

Crossing over

Exchange of genetic material between homologous chromosomes during prophase I, producing recombinant chromatids.

Chiasmata

Points where homologous chromosomes are held together during crossing over.

Recombination

New combinations of alleles formed on chromatids after crossing over.

Random/independent assortment

Orientation of homologous chromosomes at metaphase I is random, increasing variation.

Genetic variation

Differences among offspring due to meiosis and sexual reproduction.

Non-disjunction

Failure of homologous chromosomes or sister chromatids to separate, producing abnormal gametes.

Aneuploidy

Gametes with missing or extra chromosomes leading to abnormal zygotes.

Monosomy

Loss of one chromosome in a chromosome set.

Trisomy

Gain of an extra chromosome in a chromosome set.

Down syndrome

Trisomy 21; three copies of chromosome 21.

Mendel’s Law of Segregation

Alleles separate during gamete formation so each gamete carries only one allele for each gene.

Law of Independent Assortment

The segregation of alleles for one gene is independent of the segregation of alleles for any other gene.

Principle of dominance

Dominant alleles will be expressed over recessive alleles in a heterozygote.

Genotype

The gene composition for a specific trait.

Phenotype

The observable trait, determined by genotype and environment.

Homozygous

Maternal and paternal alleles are the same for a gene.

Heterozygous

Maternal and paternal alleles are different for a gene.

Hemizygous

Only one allele present for a gene (often refers to genes on the X in males).

Punnett square

A diagram used to predict genotypic and phenotypic ratios in a cross.

Co-dominance

Both alleles are expressed equally in the phenotype of a heterozygote.

ABO blood groups

System where A and B alleles are co-dominant and O is recessive.

IA

Allele for A antigen in the ABO system.

IB

Allele for B antigen in the ABO system.

i (O)

Allele with no A or B antigen; recessive in the ABO system.

X-linked inheritance

Genes located on the X chromosome; often shows distinct inheritance patterns.

Haemophilia

X-linked recessive disorder affecting blood clotting.

Red-Green colour blindness

X-linked recessive condition from mutations in retinal pigments.

Mutagens

Agents that increase the rate of genetic mutations (e.g., radiation, chemicals, some viruses).

Gel electrophoresis

Technique to separate DNA or proteins by size/charge on a gel.

DNA profiling

Identification by comparing DNA patterns, often using STRs.

Short tandem repeats (STRs)

DNA sequences of repeating units used in profiling.

cDNA

DNA synthesized from an mRNA template via reverse transcription.

Microarray

Collection of DNA sequences attached to a surface to measure gene expression.

Gene transfer

Introducing a gene into a host cell; often via a vector.

Vector

Vehicle (e.g., plasmid) used to deliver genetic material into a cell.

Plasmid

Small circular DNA that replicates independently in bacteria and can carry foreign genes.

Restriction endonuclease

Enzyme that cleaves DNA at specific sequences to create ends for joining.

DNA ligase

Enzyme that joins DNA fragments by forming phosphodiester bonds.

Recombinant DNA

DNA molecules formed by combining DNA from different sources.

Somatic Cell Nuclear Transfer (SCNT)

Cloning method where a somatic nucleus is transferred into an enucleated egg cell.

Clones

Genetically identical organisms or cells derived from a single ancestor.

Natural cloning

Asexual reproductive methods producing genetically identical offspring (binary fission, budding, fragmentation, parthenogenesis, vegetative propagation).

Totipotent

Cells able to develop into all cell types, including extraembryonic tissues.

Pluripotent

Embryonic cells capable of forming many, but not all, cell types.

Stem cells

Cells with the potential to differentiate into multiple cell types.

Monozygotic twins

Identical twins from one fertilized egg; genetically identical.

Dizygotic twins

Fraternal twins from two separate eggs fertilized by two different sperm.

Embryonic cells

Pluripotent cells that can be separated and later used to form an embryo.

Chorionic Villus Sampling (CVS)

Prenatal test removing placental tissue around 11 weeks to test fetal genes.

Amniocentesis

Prenatal test removing amniotic fluid around 16 weeks to analyze fetal cells.

Nuchal translucency scan

Ultrasound measure of nuchal fluid in early pregnancy; excess fluid linked to Down syndrome.

GMO

Genetically Modified Organism; organisms with altered genetic material.

Bt corn

Genetically modified maize producing a toxin to target certain pests.

Transgenic

Organism incorporating a gene from another species.

Gene therapy

Inserting genes to treat hereditary diseases (e.g., ADA deficiency/SCID).

Gene silencing

Process by which a cell prevents expression of a gene.

Gene knockout

Technique to inactivate a specific gene in an organism.

Cre-LoxP system

A site-specific recombination system used to create conditional gene knockouts.

Cre recombinase

Enzyme that excises DNA between LoxP sites in tissue-specific contexts.

LoxP sites

DNA sequences flanking a gene to allow Cre-mediated recombination.

Conditional knockout

A knockout allele expressed only in certain tissues or times.