Inglês para Genética: Vocabulário e Frases Essenciais

"allele"

one of two or more alternative forms of a gene that occupy the same locus on homologous chromosomes

"The patient carried one normal allele and one mutant allele of the CFTR gene, making her a carrier."

"locus (plural: loci)"

the specific fixed position on a chromosome where a particular gene or genetic marker is located

"Researchers mapped the disease locus to a 2-megabase region on chromosome 17."

"genotype"

the full genetic constitution of an organism, or the specific combination of alleles at one or more loci

"Individuals with the AA genotype at this SNP have a significantly lower risk of developing the condition."

"phenotype"

the observable physical or biochemical characteristics of an organism, resulting from the interaction of its genotype with the environment

"Despite sharing the same genotype, twins can differ in phenotype due to epigenetic and environmental factors."

"dominant allele"

an allele whose associated trait is expressed in heterozygous individuals, masking the effect of the recessive allele

"Huntington's disease is caused by a dominant allele, so a single copy is sufficient to cause the disorder."

"recessive allele"

an allele whose associated trait is expressed only when two copies are present; it is masked by a dominant allele in heterozygotes

"Cystic fibrosis follows an autosomal recessive pattern, requiring two copies of the recessive allele."

"point mutation"

a change in a single nucleotide in a DNA sequence, which may alter the amino acid sequence of the encoded protein

"The sickle-cell disease phenotype arises from a single point mutation in the beta-globin gene."

"frameshift mutation"

an insertion or deletion of nucleotides that is not a multiple of three, disrupting the reading frame of the downstream coding sequence

"A frameshift mutation in exon 2 introduced a premature stop codon, resulting in a truncated, non-functional protein."

"whole-genome sequencing (WGS)"

a laboratory process that determines the complete DNA sequence of an organism's genome at a single time

"Whole-genome sequencing of the tumour sample revealed a novel somatic mutation in TP53."

"single nucleotide polymorphism (SNP)"

a variation in a single nucleotide position in the genome that differs between individuals in a population

"A genome-wide association study identified three SNPs significantly associated with type 2 diabetes risk."

"next-generation sequencing (NGS)"

high-throughput DNA sequencing technologies that enable the parallel sequencing of millions of fragments simultaneously

"Next-generation sequencing platforms have reduced the cost of sequencing a human genome to under $1,000."

"reference genome"

a curated digital DNA sequence database assembled from the genetic material of one or more individuals, used as a comparative standard

"Reads from the clinical sample were aligned against the human reference genome GRCh38."

"coverage (sequencing depth)"

the average number of times each nucleotide in a genome is read during sequencing, influencing variant-calling accuracy

"Clinical diagnostic panels typically require a minimum coverage of 20× to reliably call heterozygous variants."

"variant calling"

the process of identifying differences between a sequenced genome and a reference genome, including SNPs, insertions, and deletions

"Variant calling using the GATK pipeline identified 4.2 million variants relative to the reference genome."

"copy number variation (CNV)"

a structural form of genetic variation in which sections of the genome are duplicated or deleted, altering the number of copies of specific genes

"Copy number variation at the BRCA1 locus was detected by array comparative genomic hybridisation."

"exome sequencing"

sequencing of all the protein-coding regions of the genome (exons), which comprise roughly 1–2% of the total human genome

"Exome sequencing of the proband and both parents enabled rapid identification of the causative de novo variant."

"DNA methylation"

the addition of a methyl group to a cytosine base in DNA, typically at CpG sites, commonly associated with gene silencing

"Hypermethylation of the MLH1 promoter is a frequent epigenetic event leading to loss of mismatch repair in colorectal cancer."

"histone acetylation"

the addition of acetyl groups to lysine residues on histone proteins, generally loosening chromatin structure and activating gene transcription

"Treatment with HDAC inhibitors increased histone acetylation at the target locus, restoring gene expression."

"chromatin remodelling"

the dynamic modification of chromatin architecture that controls access of transcription factors and other proteins to DNA

"SWI/SNF chromatin remodelling complexes are frequently mutated in human cancers, impairing gene regulation."

"CpG island"

a region of the genome containing a high frequency of CG dinucleotide sequences, often found near gene promoters

"The gene's CpG island was unmethylated in normal tissue but densely methylated in the tumour."

"imprinting (genomic imprinting)"

an epigenetic process by which certain genes are expressed in a parent-of-origin-specific manner

"Loss of imprinting at the IGF2 locus is associated with an increased risk of colorectal cancer."

"non-coding RNA (ncRNA)"

functional RNA molecules that are transcribed from DNA but not translated into protein, including miRNAs, lncRNAs, and piRNAs

"A long non-coding RNA was found to act as a molecular scaffold, organising a repressive chromatin complex."

"histone modification"

covalent post-translational modifications on histone proteins — including methylation, acetylation, and phosphorylation — that regulate chromatin state and gene expression

"H3K4 trimethylation is a histone modification marking the promoters of actively transcribed genes."

"epigenetic reprogramming"

the global erasure and re-establishment of epigenetic marks, occurring naturally during early development and in germ cells

"Induced pluripotent stem cell generation requires extensive epigenetic reprogramming of somatic cell chromatin."

"CRISPR-Cas9"

a bacterial adaptive immunity system repurposed as a precise gene-editing tool, using guide RNA to direct the Cas9 nuclease to a target DNA sequence

"CRISPR-Cas9 was used to knock out the CCR5 gene in patient-derived T cells, conferring resistance to HIV."

"guide RNA (gRNA)"

a short synthetic RNA molecule that directs the Cas9 protein to the specific genomic target sequence during CRISPR-based editing

"Researchers designed a guide RNA targeting exon 51 of the dystrophin gene to restore the reading frame."

"off-target effect"

unintended cleavage or modification at genomic sites that share sequence similarity with the intended target, a key safety concern in gene editing

"Whole-genome sequencing was performed to evaluate off-target effects before advancing the therapy to clinical trials."

"homology-directed repair (HDR)"

a precise DNA repair pathway that uses a provided template to introduce specific sequence changes at a CRISPR cut site

"Homology-directed repair was used to correct the single-nucleotide mutation responsible for the patient's haemoglobin disorder."

"non-homologous end joining (NHEJ)"

an error-prone DNA repair pathway that ligates broken DNA ends together, often introducing small insertions or deletions

"NHEJ at the Cas9 cut site introduced a 2-bp deletion that disrupted the open reading frame of the target gene."

"base editing"

a CRISPR-based technique that converts one DNA base to another (e.g. C to T) without introducing double-strand breaks

"Base editing corrected the pathogenic C-to-T transition in patient cells with an efficiency exceeding 60%."

"prime editing"

an advanced gene-editing approach that combines a modified Cas9 nickase with a reverse transcriptase to write new genetic information directly into a specified genomic site

"Prime editing was used to install a precise 3-bp correction without detectable indels or large deletions."

"viral vector"

a modified virus used as a vehicle to deliver genetic material into cells; lentiviral and AAV vectors are commonly used in gene therapy

"An AAV9 viral vector was used to deliver the SMN1 gene directly to motor neurons in infants with spinal muscular atrophy."

"autosomal dominant"

a pattern of inheritance in which a single copy of a mutated gene on an autosome is sufficient to cause disease

"Marfan syndrome follows an autosomal dominant inheritance pattern, with a 50% transmission risk per pregnancy."

"autosomal recessive"

a pattern of inheritance in which two copies of a mutated gene are required to cause disease; carriers with one copy are typically unaffected

"Phenylketonuria is an autosomal recessive disorder caused by mutations in the PAH gene."

"X-linked inheritance"

a mode of inheritance in which the mutated gene is located on the X chromosome, causing different manifestation in males and females

"Haemophilia A follows an X-linked recessive inheritance pattern; females are carriers while males are typically affected."

"penetrance"

the proportion of individuals with a given genotype who exhibit the associated phenotype; can be complete or incomplete

"BRCA1 mutations show incomplete penetrance; not all carriers will develop breast or ovarian cancer."

"expressivity"

the degree to which a phenotype is expressed in individuals who carry the causative genotype, which can vary widely even within a family

"Neurofibromatosis type 1 shows variable expressivity, with manifestations ranging from café-au-lait spots to severe complications."

"de novo mutation"

a genetic alteration that is present in a child but not inherited from either parent; it arose spontaneously in the germline or early embryo

"Whole-exome sequencing confirmed that the pathogenic variant was a de novo mutation not found in either parent."

"haploinsufficiency"

a condition in which a single functional copy of a gene is insufficient to produce a normal phenotype, so that loss of one copy causes disease

"Many transcription factor genes cause developmental disorders through haploinsufficiency when one allele is deleted."

"trinucleotide repeat expansion"

a type of mutation in which a three-nucleotide sequence is repeated a pathologically large number of times, causing disease when the repeat count exceeds a threshold

"Huntington's disease is caused by a CAG trinucleotide repeat expansion in exon 1 of the HTT gene."

"pedigree analysis"

the systematic examination of a family tree diagram showing the occurrence of heritable traits or diseases across multiple generations

"Pedigree analysis over three generations was consistent with autosomal dominant inheritance with full penetrance."

"carrier testing"

genetic testing offered to individuals who may carry one copy of a disease-causing recessive allele without showing symptoms themselves

"The couple requested carrier testing for spinal muscular atrophy before attempting conception."

"variant of uncertain significance (VUS)"

a genetic change whose association with disease risk has not yet been clearly established, requiring cautious clinical interpretation

"The laboratory reported a variant of uncertain significance in BRCA2, which complicated the counselling session."

"pathogenic variant"

a genetic change that has been established as a cause of disease based on clinical, functional, and population evidence

"The identified pathogenic variant in MYBPC3 explained the patient's hypertrophic cardiomyopathy."

"preimplantation genetic testing (PGT)"

genetic analysis of embryos created by in vitro fertilisation before transfer to the uterus, to select embryos free of a specific genetic condition

"The couple opted for preimplantation genetic testing to avoid passing on the BRCA1 mutation to their child."

"non-invasive prenatal testing (NIPT)"

a screening method that analyses cell-free foetal DNA in maternal blood to assess the risk of chromosomal conditions such as trisomy 21

"Non-invasive prenatal testing at ten weeks of gestation indicated a high risk for Down syndrome, prompting referral for diagnostic amniocentesis."

"informed consent"

the process by which a patient receives comprehensive information about a genetic test or procedure and voluntarily agrees to proceed

"Informed consent for genome sequencing must address incidental findings and the implications for other family members."

"recurrence risk"

the probability that a genetic condition will occur again in subsequent pregnancies or in other family members

"For an autosomal recessive condition, the recurrence risk for future pregnancies of two carrier parents is 25%."