Question

Pedigree & genetics pedigree
I need someone who's good at it & can tutor me more or less. I do have the basics of it but dont remember as much, & genetics one, not too familiar with it. I have a worksheet to practice on.
Anyone?

Answer 1

sure..i can..:)

Answer 2

oh thanks!

Answer 3

as starting i wish to recall my memory, so i'll be doing few basics
http://prntscr.com/6fshir

Answer 4

in first one, I just say which by I or II or III representing generation and then number?

Answer 5

I - 1
II - 2, 3, 7
III - 3

Answer 6

yeah I II III represent generations and 1 2 3 represent members of that generation.
No it I- 1
II- 1,2
and so on

Answer 7

yeah u r right..:P

Answer 8

alright
so in second one
i dont really get this one
can u decide if the trait is dominant just by looking at this pedigree?

Answer 9

yes...see they have given that either u hv the disease or u dont..u cant be a carrier.
To be a carrier..the trait needs to be recessive and genotype heterozygous

Answer 10

to find out whther the trait is ddominant or recessive from a pedigree..u try using both..once dominant and once recessive and then assign the genotype..the one that fits the correct is correct..:)

Answer 11

so its this statement ' to be a carrier, the trait has to be recessive and genotype has to be heterozygous' is it always true or is it true just exclusively for this current case?

Answer 12

yep...see for eg...a disease is due to dominant allele
then HH is diseased and Hh is diseased while hh is not
for recessive causing the disease.
HH will be normal
Hh will be normal but carrier
hh will be diseased

Answer 13

so if disease only occurs by being dominant
HH = disease
Hh = carrier
hh = disease free

if only occurs by being recessive
HH = disease free
Hh = carrier
hh = disease

did i get your point?

Answer 14

no no..see when we say carrier..it means that u dont show the disease symptoms but u hv one allele coding for the disease. Generally if the disease is resessive and the genotype is Hh. Then the normal dominant allele wud be expressed and the diseases resessive would not. so u do not show the symptoms but still hv the allele

Answer 15

but if the disease is dominant and genotype is Hh the dominant diseased allele would be expressed against the resessive. so that person shows the diseased symptoms..

Answer 16

hmmm
Hh recessive, dominant trait shown = disease free (by this i mean no symptoms) but carrier
Hh dominant, dominant trait expressed = diseased?

Answer 17

yep..perfect..:)

Answer 18

oh i see!
but in our case
the disease is caused only if its fully recessive right?

Answer 19

in our case..they say..either u hv the disease or dont...no carrier

Answer 20

since the q says, there are no carriers, then mother is not a carrier but it is heterozygous
since i counted they have 6 children
of which 3 are diseased

Answer 21

so heterozygous would not be a carrier? but only recessive will be diseased

Answer 22

in our case HH nd Hh will give hutington's disease
while hh will give normal

Answer 23

oh wow

Answer 24

see wait...

Answer 25

i thought hh would give

Answer 26

and HH & Hh would not
since there are no carriers so no heterozygous

Answer 27

or did i get it wrong? #_#

Answer 28

see..lets start from the beginning...
dont consider a disease for now..okay
we have 2 alleles..H and h. H gives blue color and h gives white

Answer 29

okay

Answer 30

so if we have HH then we get blue color
Hh blue color and
hh white color...perfect?

Answer 31

Hh carrier but blue? is that how it is?

Answer 32

H is the dominant allele....when it is present with h..only H is expressed. thats y it is called dominant

Answer 33

ah i see

Answer 34

Lets clear this once again
Hh is heterozygous..
So i n this the dominant allele H always masks rhe expression of h. H doesnt allow h to express

Answer 35

with me?

Answer 36

okay

Answer 37

so when u have Hh u dont have both white and blue colour...u have only blue

Answer 38

yes i got it
my confusion regarding carrier is still there though
i get it that dominant H is expressed over recessive h
and thus the color of the offspring is blue, but, would this offspring still be considered lets say as carrier of white color in its genotype, yes or no?
just yes or no would clear out my confusion

Answer 39

Now we consider a faulty H. this faulty H is causing hutingtons
So when u have genotype
HH u only hv faulty allele...so u hv disease
When we have Hh. u have both alleles. but the faulty is dominant. so it doesnt allow the expression of h. so u hv the disease
and when hh..no faulty allele no disease

Answer 40

oh! i seee!!!

Answer 41

now u consider a faulty h. this is not in our case but just eg.
HH..no faulty allele...normal
Hh have faulty allele. but H doesnt allow faulty h to express. so no disease. But u still hv the faulty h. so carrier.
hh..both faulty alleles. so disease.

Answer 42

so then if disease is on H
HH = disease
Hh = disease
hh = disease free
if disease is on h
HH = disease free
Hh = disease free since H is dominant thus is expressed, but still is a carrier of h
hh = diseased

Answer 43

did i get you now?

Answer 44

Carrier is mostly used in case of a disease..now white color for eg is not a disease..just another phenotype...
generally when u talk about a disease then u say carrier

Answer 45

PERFECT!!:)

Answer 46

yey! good i got it! so i consider issue of carrier in case if the faulty allele is recessive!

Answer 47

@Somy I need to go now...
yes..what u said is correct..and the genotype is heterozygous

Answer 48

ah okay, thanks for explaining so far!
been a big help!

Answer 49

:*
ill be back for the rest..:)

Answer 50

thnks!! :*

Answer 51

um can we say that if two normal parents produce an offspring which is affected....then the whole pedigree is considered to be recessive ?

Answer 52

No, that could just be a mutation in the child.

Answer 53

yeah that could be a somatic mutation...:)
@somy ..tag me when u need help for the next ques..:)

Answer 54

will do! @shrutipande9 i have actually quite few of them
so i can only ask you if you are free enough lol