week 3

Question 1

what is conventional cytogenetics

Answer 1

Metaphase chromosome analysis

G-banding

Question 2

what is molecular cytogenetics?

Answer 2

cytogenic analysis at the molecular resolution at all stages of the cycle –> DNa or in situ

Question 3

at what stage of the cell cycle is the chromsome most visible?

Answer 3

at the metaphase stage during mitosis –> this is around 15 minutes long

Question 4

what is the G1 stage of cell cycle?

Answer 4

cellular content excluding the chromosome is doubled and this take 6-12 hours

Question 5

what is the S stage of cell cycle?

Answer 5

each of the 46 chromosomes are duplicated –> 6 too 8 hours

Question 6

what is the G2 stage of cell cycle?

Answer 6

the cell double checks the chromosome for any erros and makes repairs . 3 to 4 hours

Question 7

how many bands are there on a chromsome?

Answer 7

550 –> there are bands within bands –> 30000 genes

each band has about 50 genes

Question 8

explain the chromosome structure

Answer 8

centromere in the middle. Telemore at the ends. P is the short arm and Q is the long arm

Question 9

types of cytogenic abnormalities?

Answer 9

numerical and structural

Question 10

what signs can there be that someone has a cytogenic abnormalty?

Answer 10

organ malformation, falcial dysmorphism. Comprised mental and intellectual functioning –> however this has a longer onset time

Question 11

what does diploidy mean?

Answer 11

two sets of chromosomes

Question 12

what is aneuploidy?

Answer 12

the gain or loss of a chromosome

Question 13

what is polyploidy?

Answer 13

this is the gain or loss of a whole set of chromosome

Question 14

what increases the risk of errors at gametogenesis?

Answer 14

increase in age of paternal and materal, anueploidy

Question 15

what is meiotic errors ( non disjunction)?

Answer 15

failure of chromosome or chromatid to seperate

Question 16

what are the clinical features of trisomy 21?

Answer 16

Head
Eyes: upward slanting; brushfield spots
Nose: Small
Ears: abnormally shaped/low set
Tongue: protruding –> because mouth is small
General – flat face, brachycephalic, short neck
Neurological –> Learning disabilities (mild to moderate IQ 30-60)
Hands and feet
single palmar crease
short broad hands
5th finger clinodactyly
wide gap (sandal gap) between the 1st & 2nd toes

Question 17

what are the statistics for trisomy 21?

Answer 17

1/700 birthds

75% spontaneously abort

Question 18

what are the affects of trisomy 21 in adults?

Answer 18

fertility not affected for females but is for males.
life expectancy –> 55-658yrs old
medical problems
increase chance of certain cancers ( mainly leukaemia)
hypothyroidsm
alzheimers
obesity,ceoliac, arthritis, diabetes, hearing loss, seizures

Question 19

what is trisomy 18

Answer 19

edwards syndrome
1 in 6000
95% spontaneous abort
only 10% live over the age of 1

Question 20

what are the clinical implications for the head for someone with trisomy 18

Answer 20

microcephaly, low set of ears, clift lip and palate, micrognathia

Question 21

what are the clinical features of the hands and feet for trisomy 18?

Answer 21

clenched hands –> very common, rockbottom feet and overalapping fingers

Question 22

what are the organ malformation for child with trisomy 18

Answer 22

congential heart disease (90%) 
umbilical or inguinal hernia 
congential kidney abnormalities
mental retardation
short sternum
low birth weight
eye problems --> cataract and micrognathia

Question 23

what is trisomy 13?

Answer 23

Patue syndrome, 1 in 12000 live births and 95% spontaenous abortion

Question 24

what are the symptoms of patue syndrome?

Answer 24

mental retardation, small at birth, microcephaly and sloppping forehead, and also defects of the brain –> holoprosencephaly

Question 25

what are the phenotype features of trisomy 13?

Answer 25

``` Eyes – microphthalmia, coloboma, retinal dysplasia, palpebral fissures slanted polydactyly/ flexed fingers abnormal genitalia heart defect cleft lip and palate ears abnormal and low ```

Question 26

when does female and male miosis begin?

Answer 26

females miosis begins as early as 5 months of development and finishes at puberty. However in males does not start till puberty

Question 27

what are the two steps that can causes autosomal aneuploidy for the prenatal fetus?

Answer 27

unfavourable chiasmata distribution (foetus) and also age dependent deterioation of the fetus --> as the female gets older the more affect the enviroment such as radation, alcohol, drugs has on there uterus

Question 28

is the phenotype less affected in sex chromosome mutation or autosomal ones?

Answer 28

sex chromosomes

Question 29

what is the chromosome strcuture for klinefelter and Turners syndrome?

Answer 29

Turners is 45 (x) --> 1 in 2500 | Klinefelter is 47 (XXY) 1 in 1000

Question 30

what are the features of turners syndrome?

Answer 30

reproductive --> loss of ovarian function, won't go through puberty unless given some hormone treatment and infertility lymphatics --> webbed neck--> swelling of hands or/& feet other--> coarctation of aorta, short stature as she does not go through puberty --> IQ normally reduced compared to SIBs

Question 31

what is the diagnosis of klinefelter syndrome?

Answer 31

64% is not diagnosed --> usually diagnosed when they try have kids --> infertile or if they develop hypogonadism

Question 32

what affect will klinefelter syndrome have on infertility

Answer 32

May lack secondary sexual characteristics Testicular dysgenesis Reduction in sperm count 30-50% gynaecomastia (20x risk breast cancer)

Question 33

what is the growth and IQ of patients with kilinefelter syndrome ?

Answer 33

will be normal when a child but accelerate very quickly --> long arms and legs IQ --> depends a lot on there family and also how many x's they have

Question 34

what are the three causes of triploidy?

Answer 34

dispermy, digny, diplospermy

Question 35

what happens with double paternal in chromosomes numbers

Answer 35

promote large placeneta and some growth delay

Question 36

what happens with double maternal in chromsomes numbers?

Answer 36

tiny placenta, significant delay in growth and head-saving macrocephaly due to the small placenta

Question 37

what does the paternal and maternal sex chromosome code for?

Answer 37

maternal --> foetus and paternal --> placenta

Question 38

what is mosaicism ?

Answer 38

it is miototic non disjunction

Question 39

what is reciprocal translocation?

Answer 39

when two parts of different chromosomes swap --> 1 in 500 chance. 5-10% phenotype risk reproductive risk

Question 40

what the acrocentric chromosomes?

Answer 40

13,14,15,21 and 22 --> shorter chromosomes

Question 41

what is robertsonian translocation?

Answer 41

it is when 2 acrocentric chromosomes come together and the long q arms join together and discard of the short arms

Question 42

what is unbalance rearrangment?

Answer 42

the gain or loss of huge amount of chromosomes/DNA --> can cope with gain a lot better than loss. It is usually sporadic and can be due to deletion or duplication

Question 43

what is . Interstitial deletion?

Answer 43

when a section of a chromosome is lost

Question 44

what is terminal deletion?

Answer 44

when a chuck of chrosome is lost from teh terminal ends

Question 45

what is duplication of a chromosome?

Answer 45

when a section of the chromosome is duplicated

Question 46

what is a ring chromosome?

Answer 46

when bits of either end of the chromosome breaks and forms a ring