L40 Karyotyping and X-linked disorders

Question 1

what is sex linked inheritance?

Answer 1

it refers to the pattern of inheritance shown by genes present on either of the sex chromosome

Question 2

X-Linked recessive inheritance?

Answer 2

$ observed mainly in males, if male have 1 mutant allele of his X chromosome he is homozygous for this allele.
$ females can be affected when there father is affected and their mother is an asymptomatic carrier.

Question 3

Genetic risk of X-Linked recessive inheritance?

Answer 3

1) an affected male with X-Linked recessive inheritance having kids with a normal female will produce normal boys and all the daughters will become obligate carriers.
2) obligate carriers may transmit the trait to they sons in the next generation
3) a carrier female with X-Linked recessive inheritance having kids with a normal male will produce kids where the males have a 50% chance to being affected and females have a 50% chance to being carriers

Question 4

what is Duchenne muscular dystrophy?

Answer 4

it is caused due to X-Linked recessive inheritance transmitted only by new mutation or healthy carrier females because males do not live long enough to reproduce.

Question 5

X-Linked dominant inheritance?

Answer 5

not common and observed in males and heterozygous females too

Question 6

GENETIC RISK OF X-LINKED RECESSIVE INHERITANCE?

Answer 6

1) affected female have 50% chance to passing down the disease to her kid no matter the sex
2) affected male will pass down the trait to all his daughters but none of his sons
3) therefore there is an excess of affected females and male to male transmission is not possible, however fewer females are affected due to the X chromosome inactivation.

Question 7

X-LINKED HYPOPHOSPHATEMIA (VITAMIN D-RESISTANCE RICKETS)?

Answer 7

its an X-Linked dominant disease. normally rickets occur due to the dietary deficiency of vitamin D, but in vitamin D-resistance rickets the disorder is caused by the adequate intake of vitamin D. both males and females are affected with short stature due to the short and often bowed bones. females have less severe skeletal changes than males.

Question 8

Y-LINKED INHERITANCE?

Answer 8

only males are affected and an affected father transmits trait to all his sons and none of his daughters

Question 9

EXAMPLE OF Y-LINKED INHERITANCE?

Answer 9

genes involved in spermatogenesis are found on the Y chromosome and when these genes are deleted the person is diagnosed with azoospermia which is the absence of sperm in the semen. if the affected male have a son by the techniques of assisted reproduction his son will have the same condition.

Question 10

what is karyotyping?

Answer 10

its the process of pairing and ordering all the chromosomes of an organism providing a genome wide snapshot of an individuals chromosomes. its detects gross genetic changes either numerical or structural anomalies involving several mega bases or more DNA.

Question 11

variety of tissue types can be used a source of these cells. for cancer diagnosis specimens include tumor biopsy or bone marrow samples. for other diagnosis, karyotypes are often generated from peripheral blood specimens or a skin biopsy for parental diagnosis amniotic fluid or chorionic villus specimens are used sd the source of cells