quiz 7: genetics

what does hereditary mean?

inherited traits from birth or later in life

what is a syndrome?

multiple pathologically related anomalies

when is a phenotype?

physical, biochemical, and physiologic traits

what is genotype defined by?

one’s genes

what is genotype?

a specific set of genes

where are chromosomes located in?

nucleus of the cell

every cell in the body normally has how many chromosomes?

46

which type of cell is the exception to the 46 chromosome rule?

mature germ cells

what are examples of mature germ cells?

the ova and spermatozoa

why do chromosomes contain DNA?

to direct production of amino acids, polypeptides, and proteins

what is mitosis?

cellular division for somatic cells

what type of cells do not follow mitosis?

germ cells

what are the stages of mitosis?

1. prophase

2. metaphase

3. anaphase

4. telephase

what is meiosis?

cellular division for germ cells

how does meiosis work?

1. germ cells cut their chromosomes in half

2. germ cells become nature

how many parts of meiosis is there?

2

what happens during the first part of meiosis?

1. dna replication

2. meiosis

3. exchange of choromosomal segments

what happens during the second part of meiosis?

mitotic division

what kind of chromosomes do females have?

XX

what kind of chromosomes do males have?

XY

when is 1 X from a female chromosome inactivated?

during development

what is the inactivated portion of XX chromosomes?

barr body what

what does lyon hypothesis say about chromosomes?

males have XY, females have XX

what is DNA made of?

chains of nucleotides

when is RNA formed?

when DNA goes through transcription

what do RNA produce?

1. amino acids

2. polypeptides

3. proteins

what are the types of RNA?

1. heterogenous RNA

2. messenger RNA

3. transfer RNA

4. ribosomal RNA

what is heterogenous RNA?

precursor to messenger RNA

what does messenger RNA do?

carries messages to ribosomes in cytoplasm

what does transfer RNA do?

transfers amino acids to messenger RNA

what does ribosomal RNA do?

forms ribosomes with polypeptides

what are alleles?

genes located at the same level in homologous chromosomes

what is homozygosity?

when allelic genes are identical

what are dominant alleles?

always passed down

how many dominant alleles are needed to pass down a trait?

1

how many recessive alleles are needed to pass down a trait?

2

what are molecular abnormalities?

mutations of DNA that cannot be seen without a microscope

what are gross abnormalities?

mutations seen when there is a change of physical view of chromosomes

what are the different alterations in chromosomal numbers?

1. euploid

2. polyploid

3. aneuploid

what does euploid mean?

having a completed second set of chromosomes

what does polyploid mean?

having 3rd or 4th set of chromosomes

what does aneuploid mean?

any change in number where a complete set isn’t added

what are the types of alterations in chromosomal structure?

1. deletion

2. translocation

3. inversion

4. duplication

what is deletion?

part of chromosome is lost

what is translocation?

other portions attached to chromosome

what is inversion?

portion of chromosome upside down

what is duplication?

extra segment

what is the most frequent trisomy?

down syndrome

what is down syndrome?

when someone has a trisomy of chromosome 21

what is a trisomy?

having 3 sets of a chromosome instead of 2 like normal

what is the most frequent trisomy?

down syndrome

what are common characteristics of down syndrome?

1. slanted eyes

2. short statute

3. cardiac abnormality

4. fissured tongue

5. premature tooth loss

what is trisomy 13?

when someone has 3 copies of chromosome 13

what are characteristics of trisomy 13?

1. involves many organ abnormalities

2. bilateral cleft lip and palate

3. micropthalmia/anopthalmia

4. stunted growth

5. polydactyl

what does micropthalmia mean?

having small eyes

what does anopthalmia mean?

having no eyes

what does polydactyl mean?

having extra fingers

what is the mortality rate with trisomy within 7 months of life?

70%

what is turner syndrome?

when someone has 44 normal autosomal chromosomes, but only X instead of XX

what gender does turner syndrome have a predilection towards?

females

what does turner syndrome often present with?

neck webbing

what is klinefelter syndrome?

when someone has the presence of 1(+) extra X chromosome (ex: XXY or XXXY)

what is the most common dental finding with klinefelter syndrome?

hypoplastic maxilla

what does hypoplastic maxilla mean?

smaller maxilla

what is a deletion of cri du chat syndrome?

deletion of short arm of chromosome 5

which syndrome deletes the short arm of chromosome 5?

cri du chat syndrome

what is commonly seen in cri du chat syndrome?

1. newborns: have a cat-like cry at birth

2. mental disability

what is a deletion of wolf-hischhorn syndrome?

short arm of chromosome 4

what is deleted in wolf-hirschhorn syndrome?

short arm of chromosome 4

what is the most common dental finding of wolf-hirschhorn syndrome?

cleft palate

what does penetrance mean?

numbers of individuals affected

what is expressivity?

the range of signs/symptoms that can occur in different people with the same genetic condition

what are disorders of the periodontium?

1. cyclic neutropenia

2. papillion-lefevre syndrome

3. gingival fibromatosis

what is cyclic neutropenia characterized by?

decreased number of circulating neutrophils

when is treatment for cyclic neutropenia best?

when neutrophils are at their highest

how long do neutrophil cycles last with cyclic neutropenia?

21-27 days

what are common dental findings with cyclic neutropenia?

1. severe oral ulcers

2. periodontal disease

what is the difference between chronic and cyclic neutropenia?

1. chronic: neutrophils always low

2. cyclic: goes through cycles of neutrophils being low

is papillion lefevre syndrome autosomal dominant or recessive?

autosomal recessive

what happens with someone has papillion lefevre syndrome?

1. severe periodontitis

2. premature tooth loss

3. palmoplantar keratosis

4. inflamed gingiva

what is palmoplantar keratosis?

thick keratotic plaque on hands and feet

what are patterns of tooth loss and periodontitis with papillon lefevre syndrome?

1. eruption of primary teeth

2. periodontitis occurs

3. premature loss of these teeth

4. gingiva returns to normal appearance

5. eruption of permanent teeth

6. periodontitis occurs

7. loss of most/all teeth

8. patient is edentulous at early age

when do papillon lefevre syndrome patients usually become edentulous?

early age, teens

what treatment is used for periodontal disease in papillon lefevre syndrome?

tetracyclines and anti-microbial clearance of Aa bacteria

what treatments can stop patients from losing their teeth with papillon lefevre syndrome?

none, treatments help but do not fully fix

what is focal palmoplantar?

having keratosis on tips of fingers and toes, extending to palms and soles

what is gingival hyperkeratosis

having a band of keratosis on one’s gingiva

what is gingival fibromatosis?

gingival enlargement that develops later in life

what is gingival fibromatosis associated with?

1. laband syndrome

2. hypertrichosis, epilepsy, and mental disability

3. multiple hyaline fibromas

what are the disorders of the jaw and face?

1. cherubism

2. gardner syndrome

3. mandibulofacial dysostosis

4. gorlin syndrome

5. osteogenesis imperfecta

6. tori and exostoses

what is a cherubism?

jaw condition that causes painless bilateral swelling of posterior mandible which displaces the eyes

what are symptoms of cherubism?

painless bilateral swelling of posterior mandible

what can be moved during cherubism?

eyes

cherubism has high ___

penetrance

cherubism has variable ___

expressivity

which 2 chromosomes are cherubism mapped to?

4 and 16

when does cherubism usually develop?

2-5

do lesions with cherubism get worse after puberty?

no

when do lesions with cherubism progress until?

hits puberty

what happens to lesions with cherubism after puberty?

stabilize and regress