Pedigree Analysis

Question 1

Pedigrees

Answer 1

Used for tracking genes through generations, defining inheritance patterns, symbols show sex and genetic status, lines show descent and relationships

Question 2

Pedigree symbols

Answer 2

Square- male, circle- female, diamond- unknown

Question 3

Horizontal connect lines

Answer 3

Connects spouses

Question 4

Vertical lines

Answer 4

Lead to offspring

Question 5

Horizontal connector lines

Answer 5

Siblings

Question 6

Y-shaped connector

Answer 6

Used for twins, identical twins have a crossbar

Question 7

Double horizontal line

Answer 7

Consanguineous matings

Question 8

Filled symbol

Answer 8

Affected individuals (have the disease)

Question 9

Half-filled symbol

Answer 9

Known carriers of the disease

Question 10

Dot in the symbol

Answer 10

X-linked carrier (will not always be indicated in the pedigree)

Question 11

Slash through symbol

Answer 11

Deceased individuals, only done in small pedigrees

Question 12

Consanguinity

Answer 12

Mating of genetically related individuals, uncommon in Western countries, relatives often share common genes from ancestor, can be gene for recessive disorder

Question 13

Coefficient of relationship

Answer 13

Expression of probability of sharing a common gene from an ancestor, essentially 50% for each generation

Question 14

Probability of siblings sharing a gene

Answer 14

1/2 probability

Question 15

Probability of first cousins sharing a gene

Answer 15

1/8 probability

Question 16

Probability of second cousins sharing a gene

Answer 16

1/32 probability

Question 17

Consanguinity and probability

Answer 17

The rarer the recessive disorder, the more likely the parents are consanguineous

Question 18

X-linked dominant pedigree

Answer 18

More females affected, no father-son transmission, all daughters of affected males are affected

Question 19

X-linked recessive pedigree

Answer 19

Females more likely to be carriers, if males get one copy of the allele, they get the disease