Life Sciences: DNA, Genetics, Meiosis, and Genetic Engineering

Comprehensive vocabulary flashcards covering the molecular structure of DNA and RNA, protein synthesis, inheritance patterns, meiosis, chromosomal abnormalities, and genetic engineering techniques.

DNA (Deoxyribonucleic Acid)

A double-stranded nucleic acid arranged as a double helix that provides a blueprint for an organism's growth and development by storing hereditary information and coding for protein synthesis.

Nucleotide

The monomer building block of nucleic acids, consisting of a sugar molecule (deoxyribose in DNA or ribose in RNA), a phosphate molecule, and a nitrogenous base.

Purines

A class of nitrogenous bases made up of two fused rings of nitrogen, carbon, and hydrogen atoms; examples include adenine ($\text{A}$) and guanine ($\text{G}$).

Pyrimidines

A class of nitrogenous bases made up of a single ring of nitrogen, carbon, and hydrogen atoms; examples include thymine ($\text{T}$), cytosine ($\text{C}$), and uracil ($\text{U}$).

Chromatin

Chromosomal material made up of DNA, RNA, and histone proteins found inside the nucleus of a non-dividing cell.

Extranuclear DNA

Small quantities of DNA located outside the nucleus, specifically inside the mitochondria of plants and animals and the chloroplasts of plants.

Exons

The specific protein-coding regions of a DNA molecule, representing less than $2\%$ of human DNA.

Introns

The non-coding sections of DNA that interrupt exons; they form functional RNA molecules that carry regulatory functions.

Replication

The process occurring in the nucleus during interphase whereby an existing DNA molecule creates an identical copy of itself, catalysed by DNA polymerase.

RNA (Ribonucleic Acid)

A single-stranded nucleic acid made up of ribose nucleotides containing adenine, cytosine, guanine, and uracil (instead of thymine), functioning to carry instructions from DNA to ribosomes for protein synthesis.

Transcription

The process catalysed by RNA polymerase in which a segment of DNA unwinds and its template strand is used to synthesise a complementary strand of messenger RNA ($\text{mRNA}$).

Codon

A sequence of three nitrogenous bases on an $\text{mRNA}$ molecule that codes for a specific amino acid during protein synthesis.

Stop Codons

The three specific $\text{mRNA}$ codons ($\text{UGA}$, $\text{UAA}$, and $\text{UAG}$) that do not code for any amino acid and signal the termination of translation.

Translation

The process taking place at the ribosome where the sequence of codons on $\text{mRNA}$ directs the linking of amino acids brought by $\text{tRNA}$ molecules into a polypeptide chain.

Anti-codon

A triplet of bases found at one end of a $\text{tRNA}$ molecule that pairs complementarily with a codon on the $\text{mRNA}$ strand at the ribosome.

Gene Pool

The complete set of all genes or genetic information present within a population of sexually reproducing organisms.

Housekeeping Genes

Genes that remain active in many cell types to synthesise proteins required for fundamental, routine cellular functions.

Hox Genes

Master control genes that determine the directional pattern and body structure development of an organism from a single zygote.

Epigenetics

The biological study and mechanisms responsible for controlling gene expression by switching specific genes on or off without altering the DNA sequence.

Allele

One of two or more alternative forms of a gene located at the same locus on homologous chromosomes, responsible for controlling different versions of a trait.

Genotype

The complete genetic composition or specific combination of alleles that an organism carries on its chromosomes inherited from its parents.

Phenotype

The physical appearance or expressed characteristics of an organism, determined jointly by its genotype and environmental factors.

Homozygous

The condition of having identical alleles at a given locus on a pair of homologous chromosomes (e.g., $\text{BB}$ or $\text{bb}$).

Heterozygous

The condition of having two different alleles at a given locus on a pair of homologous chromosomes (e.g., $\text{Bb}$).

Test Cross

The breeding of an individual displaying a dominant phenotype with a homozygous recessive individual to determine whether the dominant individual is homozygous or heterozygous.

Autosomes

The $22$ pairs of homologous chromosomes in human somatic cells that are identical in shape between sexes and do not determine biological sex.

Gonosomes

The sex chromosomes ($\text{X}$ and $\text{Y}$, making up the $23^{\text{rd}}$ pair in humans) that differ in shape and determine the sex of an offspring.

Sex-linked Alleles

Genes carried exclusively on the non-homologous segment of the $\text{X}$ chromosome, resulting in conditions such as haemophilia and red-green colour blindness appearing more commonly in males.

Polygenic Inheritance

A form of inheritance in which a single trait is controlled by the cumulative interaction of more than one pair of alleles, producing a continuous range of phenotypes.

Continuous Variation

A pattern of gradual phenotypic variation in a population without distinct categories, forming a graduated series such as human height or skin colour.

Mutation

A sudden change in the genetic makeup or nucleotide sequence of an organism's DNA, altering codons and potentially producing altered or non-functional proteins.

Mutagen

An environmental agent that increases the rate of genetic mutations, including ionising radiation (ultraviolet rays, X-rays), chemical agents (formaldehyde, benzene), and biological viruses.

Single Nucleotide Polymorphism (SNP)

A point genetic variation in a DNA sequence where a single nucleotide is substituted for another, occurring roughly once in every $300$ base pairs across the human genome.

Albinism

A genetic condition caused by an inherited gene mutation resulting in the lack of the protective pigment melanin, which is normally formed by the amino acid tyrosine.

Genome

The entire, complete set of genetic instructions and genes necessary to create and maintain an organism.

Human Genome Project (HGP)

An international scientific research endeavour initiated in $1990$ to sequence all chemical base pairs of human DNA and physically and functionally map all human genes.

Genetic Counselling

A service provided by specialized healthcare professionals who analyse family pedigrees and medical histories to advise prospective parents on the inheritance risks and management of genetic disorders.

Karyotype

A visual photographic representation displaying the number, size, and shape of a cell's chromosomes arranged in homologous pairs during metaphase of mitosis.

Amniocentesis

A prenatal diagnostic procedure in which a sample of amniotic fluid containing foetal cells is removed from the uterine cavity to determine the foetus's karyotype.

Chromosome Non-disjunction

The abnormal failure of homologous chromosome pairs or sister chromatids to separate properly during anaphase I or II of meiosis.

Aneuploidy

A chromosomal abnormality characterized by having an incorrect number of chromosomes (either missing or extra) in a zygote following fertilisation involving an abnormal gamete.

Klinefelter's Syndrome

An aneuploid condition in males caused by an extra $\text{X}$ chromosome ($\text{XXY}$), resulting in physical traits such as sparse body hair, enlarged breasts, and reduced fertility.

Down Syndrome

An aneuploidy condition known as trisomy $21$ ($2n+1$) resulting in $47$ total chromosomes, characterized by developmental delays, distinct facial features, and increased incidence correlated with maternal age.

Synapsis

The pairing of replicated homologous chromosomes during late prophase I of meiosis to form bivalents.

Crossing Over

The reciprocal exchange of chromosomal segments between non-sister chromatids of homologous chromosomes during late prophase I of meiosis, forming recombinant chromatids.

Chiasmata

The X-shaped physical contact points where non-sister chromatids break and exchange segments during crossing over in meiosis.

Cloning

Any biological process utilized to produce an exact genetic copy of an existing gene, cell, tissue, or multicellular organism.

Somatic Cell Nuclear Transfer (SCNT)

A cloning method in which the nucleus from a specialized adult somatic cell is transferred into an enucleated egg and stimulated by electrical pulses to initiate embryonic development.

Recombinant DNA

A synthetic form of DNA created artificially in a laboratory by combining DNA fragments from two or more different biological sources that would not naturally occur together.

Plasmid

A small, circular, double-stranded DNA molecule found in bacterial cells that replicates independently of the main bacterial chromosome and is frequently used as a vector.

Restriction Enzymes

Enzymes that cut DNA strands at specific nucleotide recognition sequences, creating uneven fragments termed sticky ends.

DNA Ligase

An enzyme that acts as 'genetic glue' by joining the exposed ends of two single strands of DNA, splicing transgenes into plasmid vectors.

Transformation

The genetic alteration of a recipient cell or organism resulting from the uptake and genomic incorporation of introduced foreign DNA.

Micropropagation

A plant tissue culture technique used to rapidly produce clonal plantlets from small parent tissue explants cultured in sterile agar containing nutrients and plant auxins.

Polyploidy

The condition of possessing more than two complete homologous sets of chromosomes (such as triploid, tetraploid, or octaploid), widespread in flowering plants and cultivated crops.

Ti Plasmid

A tumour-inducing plasmid derived from the soil bacterium Agrobacterium tumefaciens, widely engineered to insert recombinant transgenes into plant chromosomes.

Biosafety Protocol

A subsidiary international agreement to the UN Convention on Biological Diversity enacted in September $2003$, requiring Advance Informed Agreement ($\text{AIA}$) before importing genetically modified organisms.