Exam 2: Pedigree analysis

Question 1

Pedigree

Answer 1

pictorial representation of a family history, a family tree that outlines the inheritance of one or more characteristics

Question 2

Proband

Answer 2

the person from whom the pedigree is initiated.

Question 3

Wardenburg Syndrome

Answer 3

autosomal dominant.
Deafnees
fair skin
visual problems
white forelock

Question 4

Autosomal Recessive Characteristics

Answer 4

Appears in both sexes with equal frequency.

• Traits tend to skip generations.
• Affected offspring are usually born to unaffected parents.
• When both parents are heterozygous, approximately 1/4 of the offspring will be affected.
• appears more frequently among children of consanguineous marriages.

Question 5

Autosomal dominant characteristics

Answer 5

• appears in both sexes with equal frequency.
• both sexes transmit the trait to their offspring.
• does not skip generations.
• affected offspring must have an affected parent, unless they possess a new mutation.
• when one parent is affected (heterozygous) and the other parent is unaffected, approx 1/2 of the offspring will be affected.
• unaffected parents do not transmit the trait.

Question 6

Familial hypercholesterolemia

Answer 6

• LDL levels 2x’s normal
• usually heart attacks by 35
• homozyougous for defective LDL:
• -LDL levels may be 6x normal.
• may suffer heart attack by 2 and inevitably by 20.
• said to be incompletely dominant**

Question 7

X-linked recessive characteristics

Answer 7

• More males than Females affected.
• affected sons are usually born to unaffected mothers; thus, trait skips generations.
• approx 1/2 of a carrier (heterozygous) mother’s sons are affected.
• IT is never passed from father to son.
• all daughters of affected fathers are carriers.

Question 8

X-Linked dominant characteristics:

Answer 8

• Both males and females are affected, often more females than males are affected.
• does not skip generations.
• affected sons must have an affected mother; affected daughters must have either an affected mother or an affected father.
• affected fathers will pass the trait on to all their daughters.
• affected mothers (if hetero) will pass the trait on to 1/2 of their sons and 1/2 of their daughters.

Question 9

Y linked characteristics

Answer 9

• only males are affected
• it is passed from fathers to all sons.
• it does NOT skip generations.

Question 10

Concordance=

Answer 10

percentage of twin pairs in which both members of the pair express the trait.

Question 11

Compare concordant to discordant:

Answer 11

concordant: if both members of a twin pair express a trait.

Discordant: If only one member of a twin pair expresses a trait.

Question 12

Where would you expect to see genetically influenced traits exhibit higher concordance

Answer 12

in monozygotic twins.

Question 13

What is obesity an example of?

Answer 13

• a multifactorial trait.
• obesity gene called leptin.
• leptin is produced in fat tissue and decreased appetite by affecting the hypothalamus.

Question 14

Why are adoption studies used?

Answer 14

To analyze inheritance in humans.
-Similarities between adopted children and their biological parents indicate the importance of genetic factors in the expression of a trait.

-Similarities between adopted children and their adoptive parents indicate the influence of environment factors.

Question 15

What influences body-mass index

Answer 15

Genetic factors