genetics

Question 1

what is robersornian translocation

Answer 1

a translocation of two acrocentric chromosomes with a loss of satelite material from their short arms

Question 2

what is the genetic mechanism behind imprinting

Answer 2

imprinting is when a gene can have different levels of expression depending on the parent of origin

Question 3

what is independent assortment and when does it occur

Answer 3

different genes independedntly separate from one another when reproductive cells develop. This occurs in meiosis

Question 4

what sort of disorder is haemophila A

Answer 4

x-linked recessive where clotting factor VIII is affected. Due to an inversion in the X chromosome, where the chromosome breaks in two places and segemnts become inverted.

Question 5

define homozygous

Answer 5

the presence of two identical alleles ona pair of homologous chromosomes

Question 6

define heterozygous

Answer 6

different alleles on homologous chromosomes

Question 7

what type of genetic defect occurs in Prader-Willi syndrome

Answer 7

a deletion in the long arm of chroosome 15, almost always on the fathers chromsome.

Question 8

what is the phenotype of Prader-Willi syndrome

Answer 8

Results in mental retardation, obesity in later lafe (after feeding problems in infancy)

Question 9

What is the genetic defect which occurs in Angelman syndrome

Answer 9

deletion on the maternal chromosome 15. Small heads, developmental disability, speech and balance problems, seizures, sleep problems.

Question 10

what is anticipation

Answer 10

when a gene repeats and the effects are amplified from generation to generation.

Question 11

what is de novo mutation

Answer 11

a new mutation that is nont inherited

Question 12

what is genomic imprinting

Answer 12

the differing expression of genetic material dependent on the sex of the transmitting parent

Question 13

what is germline mosaicism

Answer 13

the presence of the gonadal (or germline) tissue of two populations of cells that differ genetically

Question 14

what is variable expression

Answer 14

when there is a variation in the expression of the severity of a phenotyic features seen in people with autosomal dominant disorders

Question 15

in familial hypercholesterolaemia, the apoB/E receptor extracts what type of cholesterol

Answer 15

this is an autosomal dominant disease

Question 16

what are proto-oncogenes

Answer 16

genes which stimulate the cell to grow and divide

Question 17

what do ongogenes do, what happens if they at amplified or deleted

Answer 17

a mutated proto-oncogene which keep division turned on. Create a gain of function, are domninant in their actions, cause excessive cells to be produced.

Question 18

what do tumour suppressor genes do, what happens if they are amplified or deleted

Answer 18

work to slow or stop cell growth, when they fail growth goes on unchecked, meaning mutation is a loss of function.

Question 19

what is an example of a tumor suppressor gene

Answer 19

RB - retinoblastoma. TP53 - on chromo 17, codes for p53, which regulates cell apoptosis.

Question 20

what is fragike X syndrome

Answer 20

an X linked recessive disorder of mental retardation. Females carry, men affected. Often shows anticipation. Men have prominent ears, long faces, large jaws with learning difficulties.

Question 21

what is Soto’s syndrome

Answer 21

a genetic mutation which results in children with overgrowth (tall), learning disabilities, large heads, long narrow faces, high foreheads, flushed cheeks, small pointed chin, downward pointing eyes

Question 22

what is the karyotype and phenotype of Turner’s syndrome

Answer 22

45 X. Female disorder where one X chromosome is absent. Phenotype - webbed neck, low set ears, low hairline, short stature, swollen hands and feet at birth. Puberty and reproductive failure.

Question 23

what is the karyotype 47 XXY

Answer 23

Klinefelter’s syndrome - males with and extra X resulting in sterility, small testes, delayed or absent puberty, gynecomastia, reduced facial hair.

Question 24

what is the karyotype XYY

Answer 24

XYY syndrome, males with an extra Y chromosome. May be taller than average, often no other abnormalitites. Can have haight risk of intelectual disabilities or developmental delay.

Question 25

what is the karyotype 47 XY +18

Answer 25

trisomy 18 or Edwards syndrome. Slow interuterine growth, low birth weight, heart defects, small head, small jaw and mouth, clenched fists and overlapping fingers, Severe intellectual disability, life limiting.

Question 26

what is the karyotype 47 XY+13

Answer 26

trisomy 13 aka Patau syndrome. Often have heart defects, brin or spinal cord defects, extra fingers/toes, cleft lip/palate, hypotonia,. Often die within a few weeks, only 5-10% survive beyond the first year.

Question 27

what is the karyotype 47 XY +21

Answer 27

Down’s syndrome - intellectual disability, hypotonia, heart defects, increased risk of GOD, celiac, hypothyroidism, dementia.

Question 28

what happens during meiosis I

Answer 28

homologous chromosomes line up and exchange material (recombination). The cell splits reducing the genetic material by half.

Question 29

what happens in meiosis II

Answer 29

individual chromasomes condense (As sister chromatids), separate and then the cells divide resulting in 4 daughter cells each with once copy of each chromosome

Question 30

define chimerism

Answer 30

where an individual is composed of two different populations of cells with different genotypes

Question 31

define mosaicism

Answer 31

when a person has two different cell lines derived from a single zygote (fertilized ovum)

Question 32

what is the difference between haploid and diploid

Answer 32

haploid cells contain one set of chromosomes (23) while diploid cells contain two sets of chromosomes (2N - 46)

Question 33

What is cri-du-chat syndrome

Answer 33

an autosomal dominant deletion of the short arm of chromosome 5 resulting in infants which mew like a cat. Kids have small heads, round faces, wide set eyes and intellectual disabilities. Life limiting