Lesson 8: Pedigrees & Sex-Linkage

Question 1

what are pedigree charts

Answer 1

a special type of family tree that visually shows the inheritance of a gene- it traces the inheritance of a certain trait among members of a family

Question 2

how do we get specific info about the family from pedigree charts? (generations, numerals, etc)

Answer 2

• each gen is identified by a roman numeral
• each individual within the gen is given a arabic/regular numeral where 1 is always the oldest child
• oldest to youngest children are drawn from left to right

Question 3

genetic consellors, how do they use pedigrees and why

Answer 3

they construct and analyze pedigrees to help trace the genotypes and phenotypes of a family
- can be used to determine if and how any particular trait runs in a family
- for ex: expectant parents may want to trace how hemophilia runs in the family to know if their child is at risk

Question 4

what is hemophilia?

Answer 4

bleeding disorder- problem with a person’s blood that makes them bleed longer
- inherited disorder and not caused by anything
- lack of clotting factors that allows them to bleed longer

Question 5

missing factor 8 is what kind of hemophilia

Answer 5

hemophilia a

Question 6

missing factor 9 is what kind of hemophilia

Answer 6

hemophilia b

Question 7

why can untreated hemophilia be dangerous

Answer 7

internal bleeding can become dangerous and the deep bleeding in joints and muscles can lead to permanent disability and may be life threatening

Question 8

what are clotting factors

Answer 8

proteins in the blood that help our platelets clot blood and stop bleeds

Question 9

what is hemophilia A caused by

Answer 9

mutation in the gene that creates a deficient amount of clotting factor 8

Question 10

what is hemophilia b caused by

Answer 10

hemophilia B is caused by a deficiency in clotting factor 9

Question 11

treatments for hemophilia- how does it work

Answer 11

treatments that replace the missing factor which helps platelets clot blood better
- infusions are commonly used to replace clotting factors and is used throughout the entire person’s lifetime
- gene therapy- the missing or defective gene can be delivered into cell to produce the missing factor

Question 12

plant and animal breeders- why do they use pedigrees

Answer 12

• used to track both desirable and undesirable traits
• ex: if you have a racehorse from a long line of prize-winning horses, you may charge another farmer a higher “stud fee” because the offspring produced are more likely to have those desirable traits

Question 13

what is autosomal inheritance

Answer 13

if an allele is inherited on an autosome we say that its under the control of AUTOSOMAL INHERITANCE
- this type of inheritance affects both sexes EQUALLY and is not affected by the inheritance of sex chromosomes (not always the case)
- basically, both male and females have the same likelihood of getting the inheritance/trait

Question 14

sex linked traits?

Answer 14

if an allele is on one of the sex chromosomes, the gender of the individual will affect the inheritance of this trait
- because females are XX and males are XY
- we call these traits sex-linked

EX: allele for disorder on Y chromosomes- women will not get the disorder because they do not have the Y chromosome, thus we cannot inherit it
- however, father can pass it onto the son

Question 15

Sex-linked: x linked

Answer 15

if a genetic disorder is carried on the X chromosome we would say this is X-linked
- if the disorder is recessive, even if a male only inherits one copy of the gene he will express the disorder because he is XY
- a father also cannot pass on an X-linked trait to his sons, only his daughters
- females have two X’s so they can carry it and NOT express it BUT males cant be carriers, so they either have it or dont

Question 16

examples of X-linked traits

Answer 16

red-green colour blindness, hemophilia, male-pattern baldness
- we can use punnett squares and rules of mendelian genetics to track these kinds of traits

Question 17

Sex-linked : Y-linked

Answer 17

Y linked disorders do exist but can only be passed from father to son

Question 18

why are y-linked fewer than x-linked

Answer 18

because the Y chromosome is so much smaller than the X chromosome and has less genetic information

Question 19

what can Y-linked disorders cause in males

Answer 19

may cause reduced fertility and may required medical intervention