Genetics pedigree problems

What pattern of inheritance does this trait follow?

Child has trait but parents don’t = recessive

Both males & females have trait = autosomal

Write in genotypes of individuals to check your guessthat the trait is autosomal recessive

Aa Aa

A_ aa

Autosomal recessive can work if both parents areheterozygous. They won’t show the trait, but child can.

What pattern of inheritance does this trait follow?

Both males & females have trait = autosomal

Both parents have trait, but child does not = dominant

Write in genotypes of individuals to check your guessthat the trait is autosomal dominant

Rr Rr

rr Rr

R_ rr

What pattern of inheritance does this trait follow?

Both males & females have trait = autosomalThen take a guess if dominant or recessive.Then write in genotypes to check your guess.

If you guessed dominant, then red = RR or Rr so write R_ for each red

R_ R_ Rr rr

R_ R_ R_ R_ Rr rr Rr Rr

R_ R_ R_ R_ R_ R_ R_

Dominant works, but does not prove the trait is dominant. You must see if recessive does not work.

If you guessed recessive, then red = rr

rr rr rr Rr

rr rr rr rr rr Rr rr rr

rr rr rr rr rr rr rr

Recessive also works, so you can not tell how this trait is inherited, from the information given.

What pattern of inheritance does this trait follow?

Only or mostly males have trait = sex-linked (x-linked)Children have it, but parents don’t, so recessive

Write genotypes to test guess of sex-linked recessive

XAY

XaY

XaY

XaY XaYXAX_

XAXa

XAX_

XAX_

What pattern of inheritance does this trait follow?

Autosomal dominant because child 9 does not have it but parents 5 & 6 do.

What are the genotypes of individuals 5 and 6?

Both have to be heterozygous. They have the trait, but they can passrecessive alleles to their child 9 so she doesn’t have the trait.

Gg Gg

gg

What is the genotype of individual 9?

What pattern of inheritance does this trait follow?

Next slide shows the answers

Individual 9 genotype is As (heterozygous)

Autosomal recessive

If individuals 5 and 6 had another child, what is the probability of it being affected?

Next slide shows the answer

#5 is homozygous recessive aa and #6 is heterozygous Aa, so probability of a child getting aa is ½ or 50%