L28

Question 1

how are double mutant created ?

Answer 1

by cross over in meiosis

Question 2

why alleles can’t be located in Y chromosmes ?

why males are more affected in X linked recessive disorder?

X linked recessive inheritance!

Answer 2

bcz there were also famles with white eyes

bcz only one affected chr is enough to cause the disorder

Question 3

why he choose drosophila?

Answer 3

1- small size

2- easy to raise

3-8 chromosomes [3 pair autosomes ..1 pair allosomes]

Question 4

males produce 2 types of gametes [X ,Y]

famle only one type [X]

Answer 4

😘

Question 5

new combination of gametes depend on ?

Answer 5

distance of cross over occure between 2 homologous chr in gametogenesis [first phase of mioses prophase -meiotic cell division-]

Question 6

false or true

the grater the distance between 2 gene the higher the chance of cross over so that mean higher number of recombinaation and vice versa

Answer 6

true

Question 7

can the grand father passes X linked white eyes to his son ?

Answer 7

yes he can through his red eyes having carrier daughter

Question 8

how morgan identify the position of 3 genes ?

Answer 8

by crossed the different combination of male and famle mutant flies and based on the freq of recombinants obtained he constructed the linkage map and identify the positions

Question 9

what are the 2 type of chromosomes ?

Answer 9

1-autosomes

2-allosomes [sex chromosomes]

Question 10

morgan demonstrated that ?

Answer 10

1-X chromosomes control somatic characters [X linked characters]

2-inheritance of these characters called X linked inheritance

[he use drosophila]

Question 11

true or false

the likelihood of crossing over depend on the distance between the two gene .. crossing over is more likely to occur between genes that are far apart from each other

Answer 11

true

Question 12

what is map units?

Answer 12

distance of gene expressed as map units and it indicate relative distance and order but this is not precise location of genes

Question 13

what is X linked recessive disorder?

Answer 13

color blindness

muscular dystrophy

hemophilia

fragile X syndrome [unusual X inheritance]

Question 14

what is X linked dominant?

Answer 14

hypophosphatemic

Question 15

true or false

affected man can pass thier disease [X linked disorder] to thier sons

Answer 15

false !!!!! affected man never pass thier disease to thier son bcz there os no male to male transmiddion of the affected X chr [but they can pass the disease to thier doughteاذا كانت الام حامله الصفهr]

and also he can affect his grand son through carrrier daughter

Question 16

true or false

the 50% of the children will inherit the normal copy of chr

Answer 16

true

25% affected son

25% carrier daughter

50% normal baby

Question 17

why color blindess occure ?

Answer 17

bcz THERE IS A mutations[طفره] in OPN1LW [RED]

and OPN1MW1[GREEN]

Question 18

WHAT IS fragile x syndrome?

Answer 18

it associated with the exapansion of CGG

if it [CGG] repeat more than usual number it will decrease the expresssion of FMR1 protain [located in X chr] which is required for normal neural development

Question 19

what is familia hypophosphatemia ?

Answer 19

is linked X domininat

impaired transport of phosphate and vitamin D in the kidneyes

causes softening og bones and skeletal defect called osteomalacia

it caused by mutation in phosopte

male and famle are equally affected