clinical genetics

Question 1

what are multifactorial genetic disorders?

Answer 1

disorders affecred by environmental and genetic factors

one organ system affected

Question 2

what are single gene genetic disorders?

Answer 2

mutation in a single gene which affect protein in the body

dominant/recessive patterns

Question 3

what are chromosomal genetic disorders?

Answer 3

thousands of genes involved
multiple organ systems affected
trisomes, deletions and duplications - translocations are inherited

Question 4

what are mitochondrial genetic disordes?

Answer 4

genetic disorders in the mitochondria - inherited from the mother

Question 5

what are somatic genetic disorders?

Answer 5

cancer

Question 6

what is penetrance?

Answer 6

the frequency with which the characteristic controlled by a gene is seen in individuals possessing it

Question 7

what is expressivity?

Answer 7

differing clinical features/ phenotype among those with the same alleles/ genotype

Question 8

give an example of a mitchondrial disorder

Answer 8

leber hereditary optic neuropathy

Question 9

when does crossing over occur?

Answer 9

meiosis II

Question 10

what is the structure of a chromosome?

Answer 10

long continuous piece of DNA with genes in linear order
chromosomes also contain RNA, histone protiens and non-histone proteins as packaging
during metaphase, chromosomes become highly condensed

Question 11

how do chromosome abnormalities cause issues?

Answer 11

they alter the amount of products of genes invovled

Question 12

what are numerical chromosome abnormalities?

Answer 12

change in number of chromosomes
aneuploidy - different number of a particular chromosome in a cell - monosomy, trisomy
polyploidy - having more that 2 paired sets of chromosomes - triploidy

Question 13

what are structural chromsome abnormailites?

Answer 13

translocations - reciprocal (exchange between 2 chromsomes) or robertsonian (part of chromsome on another)
deletions
duplications
inversions

Question 14

what are different cell line chromosome abnormalities

Answer 14

2 or more genetically different cells in the body

Question 15

what are most chromosome abnormalities caused by?

Answer 15

de novo events in meiosis

Question 16

why do new mutations increase with paternal age?

Answer 16

due to greater number of germ cell divisions

Question 17

what is mosaicism?

Answer 17

after fertilisation embryo undergoes abnormal separation of chromsomes in one of its cells in mitosis = mitotic non-disjunction
results in fetus with 2 or more populations of cells.

Question 18

give an example of mosaicism?`

Answer 18

down syndrome

2 population of cells - 45XY-21 and 47XY+21

Question 19

What is gametogenesis?

Answer 19

process by which cells undergo meiosis to form gametes

Question 20

what is non-disjunction?

Answer 20

failure of homologous chromosomes to separate properly during cell division

Question 21

what is centric fusion/robertsonian

Answer 21

breakage of 2 acrocentric chromosomes at or close to centromeres with subsiquent fusion

Question 22

what are the symptoms of down syndrome?

Answer 22

clinical features:
round face
protruding tongue
upslanting palpebral fissures
epicanthic folds 
developmental delay

Question 23

what is the cause of down syndrom?

Answer 23

trisomy 21 karyotype

Question 24

what is karyoping?

Answer 24

determination of the karyotype to detect chromosomal abnormalities

Question 25

what is the normal chromosomal karyotype?

Answer 25

46,XY or 46,XX

Question 26

What is flourescence in situ hybridization? (FISH)

Answer 26

production of FISH probes for olfactory homolgues with flourescent markers apply to chromsome that has been denatured and floursecence occurs at ;points

Question 27

what is FISH used for?

Answer 27

to detect specific DNA sequecnes in interphase nuclei or chromsomes - such as willams-beuren syndrome

Question 28

name 3 autosomal trisomies

Answer 28

down sydrome edwards syndrome patau syndrome

Question 29

what is edwards syndrome?

Answer 29

autosomal trisomy 18 multiple malformations - of heart and kidney inparticular clenched hands with overlapping fingers

Question 30

what is patau syndrome?

Answer 30

trisomy 13 multiple malformations affects midline structures - incomplete lobation of the brain, cleft lip, congenital heart disease

Question 31

what are anomalies of sex chromosome number caused by?

Answer 31

abnormal gametes with unusual complements of sex chromsomes

Question 32

what is the karyotype of kinefelter syndrome and its symptoms?

Answer 32

``` 47,XXY infertility poorly developed sexual characteristics gynaecomastia (males get boobs) and osteoporosis (weak bones) tall ```

Question 33

what is the karyotype and symptoms of turner syndrom?

Answer 33

45,X short stature, wide carrying angle of arms primary amenorrhoea congenital heart disease

Question 34

what are microdeletions?

Answer 34

chromosomal regions that are lost , too small to be observed microscopically, identified by use of specific moleuclar cytogenetic techniques

Question 35

2 example sof microdeletions?

Answer 35

DiGeorge syndrome | williams-beuren syndrome

Question 36

what are the typical facial features of DiGeorge syndrome?

Answer 36

small muth, prominant nose

Question 37

what are the typical facial feature sof williams-beuren syndrome?

Answer 37

bright eyes, wide mouth, upturned nose, long philtrum, flattened nasal bridge overly sociable

Question 38

give 4 examples of single gene disorders

Answer 38

huntingtons disease familial hypercholesterolaemia cystic fibrosis duchenes muscular dystrophy

Question 39

what are some symptoms of huntigntons disease

Answer 39

``` irritability depression involuntary movements poor coordination trouble learning new infromation trouble making decisions ```

Question 40

what is the cause of huntingtons disease?

Answer 40

altered HTT gene - the CAG repeat increases in size

Question 41

what is familial cholesterolaemia?

Answer 41

disorder if cholesterol metabolism causing premature atherosclerosis and cardiovascualr disease autosomal dominant mutation in LDLR - encodes LDL cholesterol receptor

Question 42

signs of familial cholesterolaemia?

Answer 42

high LDL | cholesterol deposits such as arcus cornealis

Question 43

what is cystic fibrosis?

Answer 43

autosomal recessive condition of defective CF gene | affects secretory glands including mucus and sweat glands

Question 44

what is duchenne muscular dystrophy

Answer 44

mutation in DMD gene which produces dystrophin absence of dystrophin cuases disorganisation of muscle and invasion by fibrous tissue =weak proximal muscles