Chapter 6 Genetics Flashcards
Genes that are located at the same level or locus in the two chromosomes of a pair and that determine the same functions or characterisitcs
Alleles
An organic compound containing an amino group NH2; amino acids are the main component of proteints
amino acid
Nonsex chromosomes, which are identical for men and women
autosomes
Condensed chromatin of the inactivated X chromosome, which is found at the periphery of the nucleus of cells in women
Barr Body
In genetics, a heterozygous individual who is clinically normal but who can transmit a recessive trait or characteristic; also a person who is homozygous for an autosomal-dominany condition with low penetrance.
Carrier
The constricted portion of chromosome that divides the short arms from the long arms
centromere
Either of the two vertical halves of a chromosome that are jointed at the centromere
chromatid
A general term used to refer to the material that forms the chromosomes
chromatin
structures located in the nucleus of cells and on which genes are found
chromosome
A congenital defect of the eye; notch on the outer area of the lower lid
Coloboma
Blood relationship; in genetics the term is generally used to describe a mating or marraige between close relatives
consanguinity
substance composed of a double chain of polynucleotides, with both chains coiled around a central axis to form a double helix; it is the basic genetic code or template for amino acid formation
DNA
deoxyribonucleic acid
Diploid
Having two sets of chromosomes; the normal constitution of somatic cells
In genetics, a trait or characterisitc that is manifested when it is carried by only one of a pair of homologous chromosomes
dominant
expressivity
The degree of clinical manifestation of a trait or characteristic
facies
the appearance of the face
Gamete
Speratozoon or ovum
Hereditary units, transmitted from one generation to another, that are made up of a sequence of nucleotides and located on a chromosome
Gene
Having more than one inheritance pattern
genetic heterogeneity
Having a single set of chromosomes’ a gamete is haploid
haploid
Heterozygote
An individual with two different genes at the allel loci
Homozygote
An individual with identical genes at the allele loci
A condition in which there is greater-than-normal distance between two paired ograns; ocular hypertelorism, a condition marked by greater-than- normal distance between the eyes
hypertelorism
Hypodontia
A developmental condition marked by fewer than normal teeth; also called partial anodontia.
Hypotrichosis
the presence of less than the normal amount of hair
Hypoplastic
Underdeveloped
A photomicrographic representation of a person’s chromosomal constitution arranged according to the Denver classification
Karyotype
Locus
The position occupied by a gene on a chromosome
Two-step cellular division of the original germ cells, which reduces the chromosomes from 4n DNa to 1n DNA
Meiosis
Metaphase is the phase of cellular division in which the chromosomes are
lined up evenly alonge the equatorial plane of the cell and in which they are most visible
Mitochondria
Cytoplasmic organelles that have their own DNA in a ciruclar chormosome
Unique DNA that is maternally inherited
Mitochondrial DNA
Way in which somatic cells divide so that the two daughter cells receive the same number of identical chromosomes
The type of hereditary pattern seen when there is more than one genetic factor involved and, sometimes, when there are also environmental factors participating in the causation of a condition
Multifactorial inheritance
A permanent change in the arrangement of genetic material
Mutation
In genetics, when chromosomes that are crossing over do not separate; therefore both migrate to the same cell
Nondisjunction
Oligodontia
A condition in which more than six teeth are developmentally absent
The process of formation of female germ cells (ova)
Egg; mature feminine germ cell
Ovum
The frequency with which a heritable trait is exhibited by individuals carrying the gene or genes that determine that trait
penetrance
The entire physical, biochemical, and physiological makeup of an individual; genotype is the genetic composition, and phenotype is its observable appearance
phenotype
A condition in which the teeth develop but do not erupt
Pseudoanodontia
A trait or characterisitc that shows clinically when a double-gene dose (homozygosity) exists in autosomal chromosomes or a single-gene dose exists in males if the trait is X-linked.
Recessive
Single strands of polynucleotides found in all cells; different type of this have different functions in the production of proteins
RNA
ribonucleic acid
Cytoplasmic organelles in which proteins are formed on the basis of the genetic code provided by RNA
Ribosome
The process of formation of spermatozoa (sperm)
Spermatogenesis
Cytoplasmic organelles in which proteins are formed on the basis of the genetic code provided by RNA
Ribosome
A mature male germ cell
Sprematozoon
Syndrome
A set of signs or symptoms (or both) occuring together
A genetic, heterogeneous condition of molar teeth with dominant and recessive inheritance patterns characterized by an enlarged pulp chamber, apical displacement of the pulpal floor, and no constriction at the level of the cemento-enamel junction
Taurodontism
The portion of a chromosome attached to another chromosome
Translocation
A pair of chromosomes with an identical extra chromosome
Trisomy
What are the stages of mitosis in order?
- Prophase
- Metaphase
- Anaphase
- Telophase
What is this?
a single strand
surgar is ribose
has uracil
RNA
ribonucleic acid
What are the four types of RNA?
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribsomal RNA (rRNA)
- hetergeneous nuclear RNA (hnRNA)
When the allelic genes are identical, the person is said to be ________ for that gene
homozygous
When the genes are different the person is said to be _________ for that gene.
heterozygous
What is a substance that enhances mitosis?
phytohemagglutinin
What substance is added to a culture after 72 hours of culture at 37 C to stop mitosis at metaphase
colchicine
A comlete second set of chromosomes, the total number being 92. This is incompatible with life.
Euploid
Three (triploid) or four (tetraploid) complete sets of chromosomes. This has been described occansionally in humans and is incompatible with life.
Polyploid
Any extra number of chromosomes that do not represent an exact multiple of the total chromosome complement (e.g. trisomy (a pari with identical extra chromosome) and monosomy ( a missing chromosome from a pair).
Aneuploid
The loss of a part of a chromosome is
deletion
A portion of a chromosome is attached to another chromosome.
Translocation
Think trans as in transient, a part of a chromosome hitching a ride with another chromosome
A portion of a chromosome is upside-down
Inversion
A chromosome is larger than normal; the extra segment is identical to a segment of the normal chromosome
Duplication
95% of cases of __________ are the result of nondisjunction, mostly associated with late maternal age at the time of conception
Trisomy aka Down Syndrome
What syndrome is this describing?
95% of cases are result on nondisjunction, mostly associated with late maternal age at the time of conception
Slanted eyes
Patients are shorter than normal, and heart abnormalities are present in more than 30% of individuals
Fissured tongue frequently present
Macroglossia
Hypodontia, abnormally shaped teeth, and anomalies in eruption with malposition and crowding of teeth are common findings
Gingival and periodontal disease has been reported in 90% of affected individuals
Trisomy 21
What syndrome is this describing?
This is characterized by multiple abnormalities in various organs. Seventy percent live-born infants die within the first 7 months of life
Cleft lip and cleft palate, microphthalmia (small eyes) or anophthalmia (no eyes), superfifical hemangioma of the forehead or nape of the neck, growth retardation, severe mental handicap, polydactyly of the hands and feet (supernumerary digits), clenching of the fist with thumb under the fingers, rocker-bottom feet, heart malformations, and several anomalies of the external genitals
Facial appearance is quite striking because of the cleft lip, cleft palate, and ocular abnormalities
Trisomy 13
Patients with this syndrome have a female phenotype
Majority of cases the karyotype has the normal 44 autosomal chromosomes and only one X chromosome.
Most cases are result of nondisjunction of X chromosome in the paternal gamete
These women are short, have webbing of the neck, and edema of the hands and feet
Low hairline on the nape of the neck
Chest broad with wide-spaced nipples
Aorta frequently is abnormal, and body hair is sparse
External genitals appear infantile, and generally the ovaries are not developed’ therefore these individuals have primary amenorrhea (abnormal temporary or permanent cessation of the menstrual cycle).
Smears taken from oral mucosa demonstrate lack of Barr bodies
Turner Syndrome
The majority of cases result from nondisjunction of the X chromosome, generally in the ova of older women. Affected indivuals have a male phenotype
Cannot be detected clincially until after puberty
Taller than normal and have wide hips and female pubic hair distribution
About 50% have gynecomastia (development of female breasts)
Maxillar slightly hypoplastic (underdeveloped)
Buccal smears reveal presence of one Barr body
The greater the number of X chromosomes, the more pronounced the clinical manifestations and the lower level of intelligence.
Maxilla becomes increasingly hypoplastic with increasing number of X chromosomes. Buccal smears show one Barr body for each extra X chromosome
Klinefelter Syndrome
example of abnormality caused by deletion of short arm of chromosome 5
exhibit catlike cry at birth and are cognitively challenged
No oral abnormalities occur
Cri du Chat (Cat Cry) Syndrome
Results from a deletion on the short arm of chromosome on the short arm of chromosome 4.
most newborns with this syndrome have cleft palate and intelligence quotients of less than 30
Wolf-Hirschhorn Syndrome
A condition with autosomal-dominant inheritance is transmitted ______ from one generation to the next
vertically
In autosomal-dominant inheritance when a person has a gene for the condition, the risk of having an effected offspring is ___ for each pregnancy
50%
An individual can carry a gene with a dominant effect without presenting any clinical manifestations. This is referred as
lack of penetrance
________ refers to the number of indivuals affected, and ________ pertains to the degree to which an indivual is affected
Penetrance
expressivity
For autosomal-recessive inheritance, individuals exhibiting an autosomal-recessive trait must be ______ for the gene
homozygous
Inactivation of one X chromosomes in female embryo
During early development (possibily end of 2nd week) genetic activitty of one x chromosome in each cell of female embryo inactivated
Activated chromosomes dispursed in nucleus
Inactivated chromosomes remain contracted when cell isn’t dividing and forms structure known as Barr body
Barr bodies are ONLY seen in female cells
Lyon Hypothesis
Amelogenesis imperfect is a condition that illustrates _______ ______
genetic heterogeneity
Genetic heterogeneity is used when a condition has more than one inheritance pattern and differences in the degree of clinical manifestations for each of the inherited varieties
What refers to characteristics or traits that are inherited by the participation of several genes. Characterisitics such as tooth shape and form and eye color are determined by this.
Oligogenic inheritance
used to describe a type of hereditary pattern seen when more than one genetic factor is involved and when environmental factors participate in the cause of a condition
multifactoral
The inheritance pattern of cyclic neutropenia is :
a. autosomal dominant
b. autosomal recessive
a. autosomal dominant
The disorder cyclic neutropenia is a cyclic decrease in the number of circulating _______ leukocytes (_______)
neutrophilic
aka neutrophils
What role does dental hygiene care have in cyclic neutropenia?
It removes local irritants and maintenance of optimal oral hygiene, reduces the risk of opportunistic infections in patients with cyclic neutropenia.
systemic manifestations of cyclic neutropenia include:
___________ _________ aka Kostmann syndrome, is another variety of neutropenia that is inherited as an autosomal recessive condition. This type is constant not cyclic.
The infraoral manifestations are constantly present.
This is a autosomal-recessive condition
Chronic neutropenia
has an autosomal-recessive inheritance pattern and is characterized by marked destrution of the periodontal tissues (periodontoclasia) of both dentitions with premature loss of teeth and hyperkeratosis of the palms of the hands and soles of the feet
Parents are generally heterozygous for the trait and unaffected
Long arm of chromosome 11 regions 14 to 21
Extensive bone loss results in teeth that appear to be floating in soft tissue when viewed radiographhically
Primary teeth lost the same sequence of eruption
All permanent teeth are lost before 14 years old, the gingiva then resumes normal appearance.
Papillon-Lefevre Syndrome
Chronic neutropenia is also know as what?
Kostmann syndrome
In this syndrome the neutropenia is constant and not cyclic. Intraoral manifestions are similar to cyclic variety which are severe ulcerative gingivits or gingivostomatitis. In addition to the gingiva, areas of ulceration can occur on the tongue and surfaces of the oral mucosa
is autosomal-recessive
characterized by marked destruction of the periodontal tissues (periodontoclasia) of both dentitions with premature loss of teeth and hyperkeratosis of the palms of hands and soles of feet (palmar and plantar hyperkeratosis)
Parents generally heterozygous for the trait
At about 1.5 to 2 years old a marked gingivoperidontal inflammatory process develops, edema, bleeding, alveolar bone resportion, and mobility of teeth with consequent exfoliation
Red, scaly keratosis develops on the palms and soles
Extensive bone loss results in teeth that appear to be floating in soft tissue on radiographs
At about 8 or 9 years old the gingivoperiodontal destruction is repeated in the same manner as occured in the primary dentition. All permanent teeth are lost before 14 years of age.
Papillon-Lefevre Syndrome
Areas of hyperkeratinization of the palms and soles and marked hyperkeratinization of the labial and lingual gingiva characterize ______ ________ and ______ _______
focal palmoplantar
gingival hyperkeratosis
areas of hyperkeratizination of palms and soles and marked hyperkeratinzation of the labial and lingual gingiva
autosomal dominant
process increases with age and becomes localized, with calluses forming on the weight-bearing areas
Oral hyperkeratinization is banklike and a few mm in width, follows the normal festooned contour of the gingiva. Free gingiva is NOT affected. Palatal and lingual mucosa occasionally affected
Focal Palmoplantar and Gingival Hyperkeratosis
The gingival enlargement generally develops early in life, and iwthin a few years the teeth are completely covered.
The extensive gingival enlargement leads to protrustion of the lips
Autosomal-dominany
Dental hygiene care can reduce risk of secondary inflammation and infection in patients
Gingival fibromatosis
autosomal dominant
in additional to gingival fibromatosis, patients have dysplastic or absent nails and malformed nose and ears because of soft pliable cartilage formation, hepatosplenomgaly (enlarged liver and spleen)
hypoplasia of terminal phalanges of the fingers and toes with a resultant frog like appearance
Laband sysndrome
autosomal-dominant
Hypertrichosis (excess hair growth)
especially of the eyebrows, extremities, genitals, and sacral region
epilepsy and mental retardation can also occur in this syndrome but are inconsistent features
Gingival Fibromatosis with Hypertrichosis Epilepsy and Mental Retardation Syndrome
autosomal-dominant
also known as Murray-Puretic-Drescher syndrome
in addition to gingival fibromatosis it is characterized by hypertrophy of the nail beds and multiple hyaline fibrous tumors developing on the nose, chin, head, back, fingers, thighs, and legs
Tumors on the extremities can produce contractures of various joints, including hips, knees, shoulders, and elbows
Gingival fibromatosis with multiple hyaline fibromas
autosomal dominant
females are generally less severly affected
short arm of chromosome 4
The first clinical manifestation is a progressive bilateral facial swelling that appears when the patient is between 1.5 to 4 years old
involvement of the mandible is most common
Displacement of the eyes is evident when the maxilla is affected
Radiographs of the jaw show typical soap bubble or multilocular appearance.
Ascending ramus and coronoid process of the mandible and extends into the molar and premolar areas but does NOT involve the condyle
Severe cases can involve full mandible but condyle is ALWAYS spared
areas of bone radiolucency occupied bly fibrous connective tissue
Most of these patients have pseudoanodontia due to bone lesion that interfere with tooth development and eruption
Cherubism
