Download Lesson 66 Pedigree Packet KEY 66 STT and

Name_________________________
Date______________
Period____________
ACTIVITY 66: PATTERNS IN PEDIGREES
As you read p. 64 - 71, answer the “Stopping to Think” questions in the space below. Be sure to write complete
sentences, and clearly convey your thoughts. Include additional GIST notes in the text boxes on the right.
What is a Pedigree?
1.a. Because orange tail is not present in parents of generation 3,
the gene for orange tail must be “recessed” by the blue gene, but
passed on to offspring. It wouldn’t show up in Gen. 3 if the
parents didn’t have the allele to pass on.
b.
Trait data shows in a family
trees=pedigree. Used instead of
breedings experiments on people, by
looking at patterns, to learn how traits
are inherited.
Squares symbolize males, circles
symbolize females
c. Because the blue-tail appears the same for TT or Tt, and
each parent can pass a T or a t, we don’t know the genpotype
by looking at the pedigree.
Learning from Data on Human Conditions
2. PKU is likely to be recessive since parents that do not have it,
Produce offspring with it. The parents are “carriers” of the
Recessive condition PKU (phenylketonuria)
Traits can be caused by a single gene
(Marfan’s syndrome) or by several
genes and environments. Pedigrees
help determine dominance or
recessiveness of traits so predictions
can be made.
PKU: cannot break down protein
3. An induvidual can only inherit a recessive trait if both parents are carriers or if one is a carrier and one has
the trait. The offsprings must receive 2 recessive alleles
Are All Hereditary Conditions Recessive?
4.Dominant: Both Gen. 1 parents have it, but produce offspring
With and without it. If polydactyly were recessive, it would be
impossible for the youngest son in Gen. 2 to be different from the
parents
Polydactyly: extra fingers or toes
The Genes for ABO Blood Groups
5. Incomplete dominance: nose length
co-dominance: spikes
Blood Type
O
A
B
AB
Possible Allele Pairs
O
O
A
O or A A
B O or B B
A B
6. Co-dominant: A and B
Recessive: O
ANALYSIS (page 71 – 73)
Incomplete dominance: a third trait
appears to heterozygous individuals
Co-dominance: both homozygous
traits show up in the heterozygous
individual
Simple dominance: One trait appears
whenever it’s allele is present, masking
a recessive allele if heterozygous
1. a. 1 and 2 are definitely heterozygous, because they both passed the O allele to one
offspring, and 7 because the “B” offspring have to have a B-O genotype
b. 3, 4, 5, and 6 appear to be homozygous since all offspring get an A and a B. However, 3
and 4 only have 1 offspring which is not enough evidence to be conclusive.
c. I can’t be certain that these not having the Type O allele, but I am more certain about 5 &
6 since they had so many AB offspring, and no other.
2. a. Jan’s condition is most likely dominant since her husband does not have it, but
most of her children do. It does not skip a generation.
b. She is most likely homozygous dominant. If she was heterozygous, the chance of
her offspring having the recessive trait would be 50-50, but only one in six of them
does.
3.a. This is most likely recessive. The second generation does not show the trait at all, but it
reappears in the third generation. Offspring who differ from both parents likely exhibiting a
recessive trait.
b. Marcus is homozygous recessive.
4.a. Likely dominant, since it does not skip a generation. If it was recessive, that would mean
partners of affected individuals are carriers which is improbable, since the condition is rare.
b. Sophia is a heterozygous, since only one of her parents has the condition.
5.a. A carrier in genetics carries a recessive allele but does not have the trait (they are
heterozygous). A disease carrier is infected with a disease-carrying micro, but does not have the
disease.
b. Genetic conditions are transmitted during/through reproduction. Infectious diseases are
transmitted by a microbe from person to person.