Basics of human genetics

Last updated: August 15, 2022

Summarytoggle arrow icon

Human genetics is the study of the human genome and the transmission of genes from one generation to the next. The human genome consists of 23 pairs of chromosomes (22 pairs of homologous chromosomes and one pair of sex chromosomes). All homologous chromosome pairs contain two variant forms of the same gene, called “alleles,” which are passed down from parent to offspring. Genetic disorders result from new or inherited gene mutations. Epigenetic regulation of gene expression encompasses mechanisms that allow regulating the expression of the genes without modification of the DNA sequence. Hereditary disorders are passed down from parent to offspring via different patterns of inheritance, including autosomal dominant, autosomal recessive, X-linked, and mitochondrial inheritance.

For an overview of DNA and RNA structure, see “Nucleotides, DNA, and RNA.”

Genes

  • Gene: a DNA segment with a nucleotide sequence encoding an RNA product that is either directly functional or encodes a protein
  • Locus: location of a gene or a particular DNA sequence (e.g., promoter) on a chromosome
  • Allele: one of the variant forms a gene can have in a population (from a particular locus)
    • Wild-type allele: the allele that encodes for the most common phenotype in a population
    • Mutant allele: any allele that does not code for the most common phenotype in a population
  • Multiple alleles: the occurrence of more than two different alleles in a population (e.g., the ABO blood group system) [1]
  • Allele frequency: the prevalence of a particular allele at a genetic locus within a population
  • Genetic polymorphism: a gene with more than one allele occupying the same locus of that gene [2]

Chromosomes

The mitotic spindle attaches to the kinetochores, not the centromeres.

Genotype and phenotype

Compared to dominant alleles, that have the same phenotypical expression regardless of the zygosity, codominant alleles express two completely different phenotypes in homozygous and heterozygous individuals.

Genetic penetrance and expressivity

Types of genetic penetrance and expressivity
Mechanism Definition Example
Penetrance
  • N/A
Complete penetrance
Incomplete penetrance
  • Phenotypical expression of a particular gene or genomic region is not observed in all individuals
Expressivity
  • The extent to which a phenotype is manifested in an individual carrying a particular genotype.
  • N/A
Variable expressivity
  • The variable phenotypic expression of a given genotype, which implies that a genetic disorder can manifest with different signs, symptoms, and degrees of severity in different individuals
Pleiotropy
  • A phenomenon in which one gene influences the development of multiple phenotypical traits
Compound heterozygosity
Anticipation (genetics)
  • A phenomenon in which disease onset occurs earlier and/or the disease manifestation is more severe in offspring than in parents.
Allelic heterogeneity
  • A phenomenon in which different mutations of the same allele result in the same phenotype
Locus heterogeneity
Linkage disequilibrium
  • The property of particular alleles at two linked loci to be expressed more or less often than would be expected in the general population
  • May vary in different populations
  • May occur in settings where allelic loci are within close proximity to each other on a chromosome, therefore decreasing the probability of DNA recombination
  • Individuals from the population who are not blood-related (i.e., in which a random association of the alleles would be expected).
Epistasis
  • The influence of the expression of one or more genes on the expression of another gene

Overview

Mutations according to the affected cell population

Terminology of chromosomal abnormalities

Most common terms of chromosomal abnormalities
Abbreviation Term Example Interpretation
del Deletion 46,XY, del(p5) Deletion of the short arm of chromosome 5 in a male individual (e.g., cri-du-chat syndrome)
dup Duplication 46,XX, dup(q3) Duplication of the long arm of chromosome 3 in a female individual
inv Inversion 46,XY, inv(3)(p23q27) Pericentric inversion of the chromosome 3 segment with breakpoints at position 23 on the short arm and 27 on the long arm in a male individual
t Translocation 46,XY, t(14;18)(q32;q21) Translocation between position 32 on chromosome 14 and position 21 on chromosome 18 in a male individual (e.g., follicular lymphoma)
rob Robertsonian translocation 46,XX, rob(14;21) Chromosomal translocation with fusion of the long arms of the acrocentric chromosomes 14 and 21 in a female individual. The short arms of the two chromosomes involved are lost.
/ Mosaicism 45,X/46, XX Presence of a normal cell population and one with X monosomy in a female individual (e.g., Turner syndrome)

Chromosomal aberrations

Introduction

Subtypes of chromosomal aberrations

Types of chromosomal translocations

All translocations are classified as structural chromosomal aberrations.

Overview of common chromosomal translocations
Translocation Gene product Associated conditions
t(9;22)
t(8;14)
t(14:18)
t(11;14)
t(11;18)
  • BIRC3
t(15;17)
t(12;21)
  • TEL
t(11;22)
  • Fusion protein EWS-FLI1

Other chromosomal aberrations

Uniparental disomy cannot be detected via karyotyping because the number of chromosomes is normal and there is no loss of genetic material.

HeterodIsomy: meiosis I error; IsodIsomy: meiosis II error

12–345: the chromosomes most frequently involved in Robertsonian translocations are chromosomes 21, 22, 13, 14, and 15.

Gene mutations

Types of gene mutations

  • Point mutation: alteration of a single DNA base pair
    • Genetic transition: the replacement of one purine with another purine (e.g., G to A), or the replacement of a pyrimidine with another pyrimidine (e.g., T to C)
    • Genetic transversion: the replacement of a purine with a pyrimidine (e.g., A to C, A to T, G to C, G to T) and vice versa
  • Deletion: loss of one or more base pairs
  • Splice site mutation
    • A genetic mutation at the specific site in between exons and introns that may cause changes in splicing that result in the inclusion of introns or the loss of exons
    • Can have a variable effect on the phenotype, depending on the exact location of the mutation
  • Insertion: addition of one or more base pairs
  • Substitution: one or more base pairs are replaced by different base pairs
  • Trinucleotide repeat expansion
    • Increased repetition of base triplets that leads to faulty protein synthesis or folding
    • Characterized by genetic anticipation
Trinucleotide repeat expansion diseases
Mode of inheritance Affected gene Chromosome Trinucleotide repeat Typical features
Huntington disease Autosomal dominant HTT 4 CAG Chorea, akinesia, cognitive decline, behavioral changes
Fragile X syndrome X-linked dominant FMR1 X CGG Large protruding chin, large genitalia (testes), hypermobile joints, mitral valve prolapse
Myotonic dystrophy Autosomal dominant DMPK 19 CTG Cataracts, premature hair loss in men, myotonia, arrhythmia, gonadal atrophy (men), ovarian insufficiency (women)
Friedreich ataxia Autosomal recessive FXN 9 GAA Ataxic gait, dysarthria, kyphoscoliosis, hypertrophic cardiomyopathy

Friedrich gave the fragile hunter my tonic: Friedreich ataxia, fragile X syndrome, Huntington disease, and myotonic dystrophy are examples of trinucleotide expansion disorders.
In Huntington disease, a CAG trinucleotide repeat leads to Chorea, Akinesia, and Grotesque behavior.
In fragile X syndrome, a CGG trinucleotide repeat leads to an X-tra large Chin and Giant Genitalia.
In myotonic dystrophy, a CTG trinucleotide repeat leads to Cataracts, Thinning hair (premature hair loss), and Gonadal atrophy.
In Friedreich ataxia, a GAA trinucleotide expansion leads to an ataxic GAAit.

Classification of gene mutations

Grade of mutational severity in ascending order: silent < missense < nonsense < frameshift

  • Frameshift mutation
  • Nonframeshift mutation
    • A mutation of a gene with the insertion or deletion of a number of nucleotides that is divisible by three.
    • These types of mutations tend to be less severe than frameshift mutations, as the missing (or added) codons often lead to partially functional peptides.
  • Nonsense mutation
  • Missense mutation
  • Silent mutation
  • In-frame deletion or insertion: deletion or insertion of three, six, nine, or more base pairs (always in triplets) without a shift in the reading frame, but with deletion or insertion of one, two, three, or more amino acids in the protein during translation
  • Loss-of-function mutation: a mutation resulting in the expression of the gene product with decreased or absent function
  • Gain-of-function mutation: a mutation that leads to either the expression of the larger amount of the gene product or increased function of the expressed gene product
  • Splice mutation: an alteration (especially point mutations) in the nucleotide sequence required for splicing (e.g., the exon-intron border or at the junction)
  • Dominant-negative mutation
    • A gene mutation that produces a nonfunctional protein that exerts a dominant effect
    • This nonfunctional protein impairs the function of the normal protein encoded by the wild-type allele in heterozygous individuals (e.g., mutant, nonfunctional p53, binds DNA and prevents the attachment of the functional p53 protein) [6]

Compared to missense or silent mutations, nonsense and frameshift mutations lead to fundamental structural changes of the coded proteins. Consequently, these mutations result in more severe disease manifestations.

STOP the NONSENSE: NONSENSE mutations create early STOP codons in the RNA.

Examples of genetic disorders by chromosome

Overview

Main mechanisms of epigenetic regulation

DNA methylation [7]

Epigenetic regulation mechanisms: Acetylation Activates DNA; Methylation Mutes DNA.

Histone modification [13][14]

Regulatory RNA [16]

Examples of processes regulated by epigenetic mechanisms

X inactivation (lyonization)

Genomic imprinting [19]

Overview

  • Definition: the study of inherited traits or disorders and their phenotypic variability over several generations in a group of blood-related individuals by way of a pedigree chart, which depicts that group's genetic history in a family tree
  • Elements
    • Circles: female individuals
    • Squares: male individuals
    • Lines between circles and squares: familial relationship
    • Roman numerals: generations
    • Arabic numbers: children of a generation in order of birth
    • Affected family members and carriers (i.e., heterozygous individuals who have the allele but are not phenotypically affected) are represented by shaded symbols.

A basic methodological approach to pedigree analysis

  • Question 1: Does every affected family member have an affected parent?
    • Yes: dominant inheritance of the trait
    • No: recessive inheritance of the trait
  • Question 2: Are the majority of affected family members male?
    • Yes: most likely X-linked recessive inheritance
    • No: Proceed to the following questions and subsequent answers.
      • Question 2a: Do all affected male family members have an affected mother?
      • Question 2b: Do all affected male family members have unaffected sons?
      • Question 2c: Do all affected male family members have affected daughters?
        • If Questions 2a, 2b, and 2c have all been answered in the affirmative, the disease most likely follows an X-linked dominant pattern of inheritance.
        • If Question 1 has been answered in the affirmative and either Question 2a, 2b, or 2c have been answered in the negative, the disorder is most likely autosomal dominant.
        • If Question 2 and Questions 2a, 2b, and 2c have all been answered in the negative, the disorder is most likely autosomal recessive.

Overview

Examples of AD inheritance patterns

AD inheritance pattern in homozygous parents
Homozygous parent (affected)
N N
Homozygous parent (unaffected) n Nn (affected) Nn (affected)
n Nn (affected) Nn (affected)
AD inheritance pattern in heterozygous and homozygous parent
Heterozygous parent (affected)
N n
Homozygous parent (unaffected) n Nn (affected) nn (unaffected)
n Nn (affected) nn (unaffected)
AD inheritance pattern in heterozygous parents
Heterozygous parent (affected)
N n
Heterozygous parent (affected) N NN (affected) Nn (affected)
n Nn (affected) nn (unaffected)

An autosomal dominant disease with complete penetrance will always manifest with clinical features in every generation.

Examples of AD disorders

Overview

Examples of AR inheritance patterns

  • Homozygous parents: no children will be affected, but all will be carriers
AR inheritance pattern in homozygous parents
Homozygous parent (unaffected)
N N
Homozygous parent (affected) n Nn (carrier) Nn (carrier)
n Nn (carrier) Nn (carrier)
  • One heterozygous and one homozygous parent: All children inherit the allele that causes the trait or disorder, but only 50% will express the trait while other 50% will be carriers.
AR inheritance pattern in heterozygous and homozygous parent
Heterozygous mother (carrier)
N n
Homozygous father (affected) n Nn (carrier) nn (affected)
n Nn (carrier) nn (affected)
  • Heterozygous parents
    • Half of the children will be carriers, 25% will express the trait, and 25% will not express the trait.
    • Healthy individuals with an affected sibling (nn) have a two-thirds-probability of being a carrier (Nn, Nn, or NN).
AR inheritance pattern in heterozygous parents
Heterozygous parent (carrier)
N n
Heterozygous parent (carrier) N NN (unaffected) Nn (carrier)
n Nn (carrier) nn (affected)

Examples of AR disorders

Overview

  • Definition: a mode of inheritance that requires two copies of an allele on the X chromosome, one from the mother and one from the father, for the phenotypical expression of a trait or disorder in offspring
  • X-linked recessive (XR) inheritance leads to the expression of the phenotype in all male children who inherit the mutated allele.
  • Female individuals are more frequently carriers (unaffected) of X-linked inherited disorders than male individuals.
  • Individuals with Turner syndrome only have one X chromosome and are, therefore, more susceptible to X-linked recessive disorders
  • Male-to-male inheritance is impossible.
  • Male individuals tend to develop a more severe form of the XR disease.
  • This type of inheritance frequently skips generations.

Examples of XR inheritance patterns

XR inheritance pattern in heterozygous (carrier) mother and hemizygous (unaffected) father
Heterozygous mother (carrier)
x X
Hemizygous father (unaffected) X Xx (daughter, carrier) XX (daughter, unaffected)
Y xY (son, affected) XY (son, unaffected)
XR inheritance pattern in heterozygous (carrier) mother and hemizygous (affected) father
Hemizygous father (affected)
x Y

Heterozygous mother (carrier)

X Xx (daughter, carrier) XY (son, unaffected)
x xx (daughter, affected) xY (son, affected)
XR inheritance pattern in homozygous (unaffected) mother and hemizygous (affected) father
Hemizygous father (affected)
x Y
Homozygous mother (unaffected) X Xx (daughter, carrier) XY (son, unaffected)
X Xx (daughter, carrier) XY (son, unaffected)
  • Homozygous (affected) mother and hemizygous (affected) father: If both parents have the trait/disease then all children will invariably be affected.
XR inheritance pattern in homozygous (affected) mother and hemizygous (affected) father
Hemizygous father (affected)
x Y
Homozygous mother (affected) x xx (daughter, affected) xY (son, affected)
x xx (daughter, affected) xY (son, affected)

Examples of XR disorders

Overview

  • Definition: a mode of inheritance that only requires one copy of a mutated allele on the X chromosome, from either the mother or father, for the phenotypical expression of the trait or disorder in offspring
  • In X-linked dominant (XD) inheritance, male and female individuals have an equal probability of inheriting the trait or disorder.
  • Because female individuals have two X chromosomes, the inheritance of an X-linked dominant disorder typically manifests in a less severe form than in male individuals.

Examples of XD inheritance patterns

XD inheritance pattern in heterozygous mother and hemizygous (unaffected) father
Heterozygous mother (affected)
X x
Hemizygous father (unaffected) x Xx (daughter, affected) xx (daughter, unaffected)
Y XY (son, affected) xY (son, unaffected)
  • Homozygous mother and hemizygous (unaffected) father: All the children will inherit the trait/disease.
XD inheritance pattern in homozygous mother and hemizygous (unaffected) father
Homozygous mother (affected)
X X
Hemizygous father (unaffected) x Xx (daughter, affected) Xx (daughter, affected)
Y XY (son, affected) XY (son, affected)
XD inheritance pattern in heterozygous mother and hemizygous (affected) father
Hemizygous father (affected)
X Y
Heterozygous mother
(affected)
X XX (daughter, affected) XY (son, affected)
x Xx (daughter, affected) xY (son, unaffected)
  • Homozygous (unaffected) mother and hemizygous (affected) father
    • All daughters will be affected.
    • Sons are invariably unaffected.
XD inheritance pattern in homozygous (unaffected) mother and hemizygous (affected) father
Hemizygous father (affected)
X Y
Homozygous mother (unaffected) x Xx (daughter, affected) xY (son, unaffected)
x Xx (daughter, affected) xY (son, unaffected)

Examples of XD disorders

Mitochondrial inheritance

Polygenic inheritance

Multifactorial inheritance disorders (MID)

  • Definition: disorders that result from a combination of mutations in multiple genes and environmental factors (e.g., type 2 diabetes mellitus, cleft palate, neural tube defects, schizophrenia, coronary artery disease)
  • Features
    • Commonly manifest with the Carter effect [21]
      • Individuals of the less commonly affected sex are more likely to pass on the disorder to their children if they develop the disease.
      • It is hypothesized the group less commonly affected possesses a higher number of susceptibility genes and the trait/disorder will, therefore, manifest less frequently, requiring more genetic loci to be affected.
      • However, the numerical increase in susceptibility genes leads to an increased probability of passing on mutated alleles to offspring.
    • Population groups with a certain heritage are more commonly affected compared to the population at large (e.g., Hispanic, Ashkenazi Jewish, West African).
    • One gender is more frequently affected.
    • Isolated occurrence is possible, but familial clustering is frequent.
  • Index case: the first person of a family to develop the trait/disorder in question
  • Threshold effect: Effect observed in some MIDs, in which the disorder only develops when genetic predispositions and external factors combine to reach a certain threshold value.
  • Gene-environment interaction: genetic predisposition affects susceptibility to the effects of environmental factors (e.g., individuals with a family history of type II diabetes may never develop the disease if they maintain a healthy lifestyle).

Terminology

  • Population (genetics): a group of individuals that interbreed and live on the same territory at the same time point
  • Gene pool: a collection of all genes found in a population
  • Genetic variation: a variation of the genome between organisms within one species

Genetic variation [22][23]

The following phenomena lead to changes in genetic variation.

  • Mutation-selection equilibrium: a balance between the rate of occurrence of deleterious alleles (alleles, which decrease the fitness of an individual) in a population and their elimination through the selection processes
  • Genetic drift
    • A change in allele frequencies in a population that occurs by chance in a finite population due to random sampling
    • Typically leads to a decrease in genetic variation
    • Can be encountered in the following scenarios:
      • Founder effect
        • A reduction in genetic variation resulting from the establishment of a new population by a small subset of a larger population
        • Example: increased incidence of maple syrup disease, polydactyly, and other conditions in Amish individuals
      • Genetic bottleneck
        • A decrease in the gene pool and genetic variation caused by a dramatic decrease in the size of a population (e.g., due to death or reduced rate of reproduction)
        • Increases risk of extinction of alleles from the population and accumulation of recessive traits
  • Natural selection
    • A process through which the population frequency of traits that increase the chance of survival of an organism increases and the frequency of traits that reduce it decreases
    • Example: there is an increased frequency of the sickle cell trait (heterozygosity for the sickle-cell allele) in the African population because it provides a relative resistance to malaria while causing only mild symptoms

Heterozygote frequency

  • Definition
    • The proportion of heterozygote carriers of an allele that causes a trait/disorder in the population
    • Used to estimate a child's risk of a recessive inherited disorder if the genotype of the parents is unknown
  • Equation: The heterozygote frequency is calculated by using the Hardy-Weinberg law, a principle that states that genetic variation in a population remains constant under a set of idealized assumptions (including random mating and no migration, mutation, or selection).
  • Example: cystic fibrosis with an incidence of ∼ 1:2,500
    • Calculate 2pq: 2pq = 2×1×1/50 = 1/25 (4%) heterozygote frequency
    • Calculate p: If (p + q)2 = 1 then p + q = 1 and p = 1 – q = 1 – 1/50 = 0.98 (98%) ≈ 1
    • Calculate q: If q2 = 1/2,500 then q = 1/50 = 0.02 (2%)
    • Since cystic fibrosis is a recessive disorder, only homozygote carriers develop the disease. The incidence corresponds to the homozygote frequency q2.
A (p) a (q)
A (p) AA (p2) Aa (pq)
a (q) Aa (pq) aa (q2)

  • Definition: introduction of genetic material into a cell to treat diseases by changing the expression of a gene or modifying cellular processes [24][25]
  • Indications
  • Modes of therapy delivery [26]
    • In-vivo
      • Gene therapy is introduced directly into the body tissues.
      • Usually targets nondividing cells (e.g., neurons)
    • Ex-vivo
      • Cells are gathered from the patient or donor, modified outside the body, and returned back to the body.
      • Usually targets dividing cells (e.g., white blood cells)
  • Methods of therapy transfer
    • Viral vectors (e.g., lentiviruses, retroviruses)
    • Liposomes
    • Polymers
    • Electroporation
      • Usage of a high-voltage electrical field for DNA delivery into cells.
      • Electrical field change permeability of the cell membrane allows for passage of the substances with large molecular weight (e.g., nucleic acids).
Examples of gene therapy agents
Drug Mechanism Indications
Onasemnogene abeparvovec
Voretigene neparvovec
  • Vector based on adeno-associated virus delivers a normal copy of the RPE65 gene to the retinal cells.
  • Retinal dystrophies associated with biallelic RPE65 mutations (e.g., Leber congenital amaurosis)
Tisagenlecleucel
Alipogene tiparvovec
Overview of clinical genetic tests [27][28]
Method Indications Benefits Limitations
Single-gene sequencing
  • Highly targeted
  • Can only be used for disorders caused by a single known variant of gene
Gene panel sequencing
  • Cost-effective
  • Can be used to test several clinical hypotheses
  • Targeted
  • A panel has a limited number of genetic variants.
  • Does not detect large copy number variations
  • Usually are not designed to test for intronic variants
Whole-exome sequencing [28]
  • Often used after more precise methods fail to reveal a causative genetic variant
  • Sometimes employed in the diagnosis of disorders with many possible causative variants
  • Can be used if a presumably causative variant is unknown
  • Reinterpretation is possible
  • High rate of incidental findings (variants of unknown significance)
  • Does not detect intronic variants
Whole-genome sequencing
  • Can detect genetic variants both in introns and in exomes
  • Expensive
  • Interpretation is difficult
Chromosomal microarray
  • Does not detect sequence changes
  • Does not detect balanced chromosomal rearrangements
Karyotyping
  • Diseases caused by structural or numerical chromosome abnormalities (e.g., aneuploidies, triploidies)
  • Cheap
  • Fast to perform
  1. Jones PA. Functions of DNA methylation: islands, start sites, gene bodies and beyond. Nat Rev Genet. 2012; 13 (7): p.484-492. doi: 10.1038/nrg3230 . | Open in Read by QxMD
  2. Payer B, Lee JT, Namekawa SH. X-inactivation and X-reactivation: epigenetic hallmarks of mammalian reproduction and pluripotent stem cells. Hum Genet. 2011; 130 (2): p.265-280. doi: 10.1007/s00439-011-1024-7 . | Open in Read by QxMD
  3. Fedoriw A, Mugford J, Magnuson T. Genomic Imprinting and Epigenetic Control of Development. Cold Spring Harb Perspect Biol. 2012; 4 (7): p.a008136-a008136. doi: 10.1101/cshperspect.a008136 . | Open in Read by QxMD
  4. Lahtz C, Pfeifer GP. Epigenetic changes of DNA repair genes in cancer.. J Mol Cell Biol. 2011; 3 (1): p.51-8. doi: 10.1093/jmcb/mjq053 . | Open in Read by QxMD
  5. Benayoun BA, Pollina EA, Brunet A. Epigenetic regulation of ageing: linking environmental inputs to genomic stability. Nat Rev Mol Cell Biol. 2015; 16 (10): p.593-610. doi: 10.1038/nrm4048 . | Open in Read by QxMD
  6. Slotkin RK, Martienssen R. Transposable elements and the epigenetic regulation of the genome. Nat Rev Genet. 2007; 8 (4): p.272-285. doi: 10.1038/nrg2072 . | Open in Read by QxMD
  7. Bannister AJ, Kouzarides T. Regulation of chromatin by histone modifications. Cell Res. 2011; 21 (3): p.381-395. doi: 10.1038/cr.2011.22 . | Open in Read by QxMD
  8. Zhou VW, Goren A, Bernstein BE. Charting histone modifications and the functional organization of mammalian genomes. Nat Rev Genet. 2010; 12 (1): p.7-18. doi: 10.1038/nrg2905 . | Open in Read by QxMD
  9. Glozak MA et al. Histone deacetylases and cancer. Oncogene. 2007 .
  10. Holoch D, Moazed D. RNA-mediated epigenetic regulation of gene expression. Nat Rev Genet. 2015; 16 (2): p.71-84. doi: 10.1038/nrg3863 . | Open in Read by QxMD
  11. Wei J-W, Huang K, Yang C, Kang C-S. Non-coding RNAs as regulators in epigenetics. Oncol Rep. 2016; 37 (1): p.3-9. doi: 10.3892/or.2016.5236 . | Open in Read by QxMD
  12. Fang H, Disteche CM, Berletch JB. X Inactivation and Escape: Epigenetic and Structural Features. Front Cell Dev Biol. 2019; 7 . doi: 10.3389/fcell.2019.00219 . | Open in Read by QxMD
  13. Ferguson-Smith AC. Genomic imprinting: the emergence of an epigenetic paradigm. Nat Rev Genet. 2011; 12 (8): p.565-575. doi: 10.1038/nrg3032 . | Open in Read by QxMD
  14. Franceschini N, Frick A, Kopp JB. Genetic Testing in Clinical Settings. American Journal of Kidney Diseases. 2018; 72 (4): p.569-581. doi: 10.1053/j.ajkd.2018.02.351 . | Open in Read by QxMD
  15. Retterer K, Juusola J, Cho MT, et al. Clinical application of whole-exome sequencing across clinical indications. Genetics in Medicine. 2015; 18 (7): p.696-704. doi: 10.1038/gim.2015.148 . | Open in Read by QxMD
  16. Storry JR, Olsson ML. The ABO blood group system revisited: a review and update.. Immunohematology. 2009; 25 (2): p.48-59.
  17. Promoting Safe and Effective Genetic Testing in the United States - Glossary. https://www.genome.gov/10002399/genetic-testing-reportglossary. . Accessed: November 1, 2020.
  18. Kuchenbaecker KB, Hopper JL, Barnes DR, et al. Risks of Breast, Ovarian, and Contralateral Breast Cancer for BRCA1 and BRCA2 Mutation Carriers. JAMA. 2017; 317 (23): p.2402. doi: 10.1001/jama.2017.7112 . | Open in Read by QxMD
  19. Nielsen J, Wohlert M. Chromosome abnormalities found among 34910 newborn children: results from a 13-year incidence study in �rhus, Denmark. Hum Genet. 1991; 87 (1): p.81-83. doi: 10.1007/bf01213097 . | Open in Read by QxMD
  20. Priya PK, Mishra VV, Roy P, Patel H. A Study on Balanced Chromosomal Translocations in Couples with Recurrent Pregnancy Loss.. Journal of Human Reproductive Sciences. 2018 .
  21. Willis A, Jung EJ, Wakefield T, Chen X. Mutant p53 exerts a dominant negative effect by preventing wild-type p53 from binding to the promoter of its target genes. Oncogene. 2004; 23 (13): p.2330-2338. doi: 10.1038/sj.onc.1207396 . | Open in Read by QxMD
  22. Anguela XM, High KA. Entering the Modern Era of Gene Therapy. Annu Rev Med. 2019; 70 (1): p.273-288. doi: 10.1146/annurev-med-012017-043332 . | Open in Read by QxMD
  23. What is Gene Therapy?. https://www.fda.gov/vaccines-blood-biologics/cellular-gene-therapy-products/what-gene-therapy. Updated: January 1, 2018. Accessed: October 27, 2021.
  24. Sinclair A, Islam S, Jones S. Gene Therapy: An Overview of Approved and Pipeline Technologies. CADTH Issues in Emerging Health Technologies. 2016 .
  25. Quintana-Murci L. Understanding rare and common diseases in the context of human evolution. Genome Biol. 2016; 17 (1). doi: 10.1186/s13059-016-1093-y . | Open in Read by QxMD
  26. Amos W, Hoffman JI. Evidence that two main bottleneck events shaped modern human genetic diversity. Proceedings of the Royal Society B: Biological Sciences. 2009; 277 (1678): p.131-137. doi: 10.1098/rspb.2009.1473 . | Open in Read by QxMD
  27. Schwartz M, Vissing J. New patterns of inheritance in mitochondrial disease. Biochem Biophys Res Commun. 2003; 310 (2): p.247-251. doi: 10.1016/j.bbrc.2003.09.037 . | Open in Read by QxMD
  28. Lisa M Kruse, Matthew B Dobbs, Christina A Gurnett. Polygenic Threshold Model with Sex Dimorphism in Clubfoot Inheritance: The Carter Effect. J Bone Joint Surg Am. 2008; 90 (12): p.2688-2694. doi: 10.2106/jbjs.g.01346 . | Open in Read by QxMD
  29. LingJiao Zhang, Vivian Y. Shin, Xinglei Chai, Alan Zhang, Tsun L. Chan, Edmond S. Ma, Timothy R. Rebbeck, Jinbo Chen, Ava Kwong. Breast and ovarian cancer penetrance of BRCA1/2 mutations among Hong Kong women. Oncotarget. 2018; 9 (38). doi: 10.18632/oncotarget.24382 . | Open in Read by QxMD
  30. Hanna J, Hossain GS, Kocerha J. The Potential for microRNA Therapeutics and Clinical Research. Frontiers in Genetics. 2019; 10 . doi: 10.3389/fgene.2019.00478 . | Open in Read by QxMD

3 free articles remaining

You have 3 free member-only articles left this month. Sign up and get unlimited access.
 Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer