De novo

Question 1

What is the inheritance of de novo mutations?

Answer 1

Autosomal dominant

Question 2

What increases the probability of a de novo mutation?

Answer 2

The older the parents are

Question 3

What do de novo mutations play an important role in?

Answer 3

severe early-onset disease

Question 4

What happens if the de novo takes place after fertilisation

Answer 4

Every cell of the individual will carry the mutation

Question 5

What happens if the de novo takes place if it takes place after a few cell divisions?

Answer 5

Only the daughter cells of those ones will carry the mutations–> mosaic individuals

Question 6

Dosage compensation

Answer 6

Mechanism equalising the dosage of X chromosome gene products between male and females

Question 7

X-inactivation

Answer 7

In mammals, dosage compensation is obtained by silencing one X chromosome in female cells

Question 8

What is every female in regards to X-inactivation?

Answer 8

Mosaic

Question 9

When does X-inactivation take place?

Answer 9

When the female embryo consists of a few hundred cells

Question 10

Mechanism of X inactivation

Answer 10

1. X-inactivation is initiated and spreads from a single site called the X-inactivation center. Within XIC, there is a lncRNA called Xist: X-inactivation specific transcript
2. Xist is expressed only from inactive X
3. Xist spreads from the XIC over the entire chromosome, using chromatin loops as shortcuts to form heterochromatin

Question 11

When is X-inactivation reversed?

Answer 11

During germ cell formation