Lec 8

Question 1

Product rule

Answer 1

if two or more events are independent of one another, the likelihood of their simultaneous occurrence is the product of their individual probabilities

Question 2

Sum rule

Answer 2

Defines the joint probability of occurrence of any two or more mutually exclusive events. The individual probabilities are summed.

Question 3

Conditional probability

Answer 3

involves questions asked after a cross has been made and is applied when info about the outcome modifies the probability calculation

Question 4

Binomial probability

Answer 4

predicting the likelihood of a series of events.

Question 5

Binomial expansion formula

Answer 5

contains two variables:
p, the frequency of one outcome
q, the frequency of the alternative outcome
(p+q)^n
n, the number of successive events

Question 6

Autosomal Dominant Inheritance

Answer 6

• “Vertical”: trait appears in each generation
• each affected individual has an affected parent
• one affected individual transmits to 1/2 the offspring (on avg.)
• two unaffected parents do not transmit the train
• two affected parents may have unaffected children

Question 7

Autosomal recessive inheritance

Answer 7

• “horizontal” transmission: trait can appear at once in siblings
• affected individuals can have unaffected parents
• if both parents are affected, all children are
• observable effect of relatedness

Question 8

Heterozygous

Answer 8

the parents of an affected individual with a recessive trait can be predicted to be “carriers”

Question 9

Heterochromatin: X inactivation

Answer 9

mammalian males and females have different # of X chromosomes: XX or XY. To address this gene dose difference, female mammals undergo random X inactivation early in development. One X is left active in each nucleus the other is almost entirely heterochromatic, forming a Barr body. The inactive X is largely heterochromatic.

Question 10

Dosage compensation

Answer 10

one X chromosome (mat or pat) is randomly inactivated during development. The inactivation is transcriptional and relies on an RNA called “XIST”. The x transcribing XIST gets inactivated.

Question 11

Process of X inactivation

Answer 11

1) Xist activation and transcription of Xist RNA
2) stable Xist RNA coats the X chromosome
3) Coat of Xist RNA leads to silencing and condensation of X chromosome
4) HMTs are attracted to RNA coating; H3 & H4 histones are deacetylated and methylated, inactivating the chromosome
5) condensed and silenced X chromosome forms Barr body

Question 12

Inheritance of an X-linked recessive trait

Answer 12

• more males than females have the recessive phenotype

- some females are heterozygous: do not show phenotype but can transmit the trait