Genomic Equivalence

Question 1

What are the three hypotheses for cell differentiation? How can we test these hypotheses?

Answer 1

1. Differential gene loss
2. Selective gene amplification
3. Genetic equivalence with differential gene expression.
   # can test with cloning!

Question 2

Describe differential gene loss hypothesis?

Answer 2

First cell has all of the genes for the organism, daughter cells only have a subset.

Question 3

Describe selective gene amplification hypothesis

Answer 3

Certain genes are preferentially amplified within cells, which affects the cell fate.

Question 4

Describe the genetic equivalence with differential gene expression hypothesis

Answer 4

(what actually happens) - Each cell has every gene. Each cell can express the genes differently to achieve different functions

Question 5

What experiments in amphibians indicate genomic equivalence of nuclei?

Answer 5

1. A somatic cell was enucleated and the nucleus and meiotic spindle was implanted into an activated egg. Clone was created, which indicates genomic equivalence because the somatic cell contained all of the information necessary for a full frog to develop.
2. Albino frog cloning. Albino nucleus donors grown in WT frogs resulted in all albino offspring.

Question 6

How does the nucleus exert its effects on differentiated cells?

Answer 6

By expressing different genes at required levels to achieve desired cell function.

Question 7

Describe experiments that resulted in Dolly

Answer 7

Udder cells were removed (original dolly), and entire cell as implanted into the egg of a Scottish Blackface surrogate. The egg and cell were fused in a petri dish, and the embryo was cultured for 7 days. The embryo was then implanted into the surrogate mother.

Question 8

(1) What is “large offspring syndrome”, and (2) what is it thought to be caused by?

Answer 8

1. Large offspring syndrome is when the clones are born much larger than normal
2. Possible explanation is imprinting, in which parental methylation patterns lack maternal and paternal patterns and thus cause LOS through (3).
3. Father contributes Insulin-like growth factor 2 (Igf2) which enhances growth, mother contributes active H19 and igf2r, which serve to reduce growth for an easier pregnancy. In LOS, the clone may lack the mother’s expression patterns and thus be dominated by the father’s ifg2 expression.

Question 9

(1) What are the two types of cloning? (2) Describe the difference between the two.

Answer 9

1. Reproductive & Therapeutic cloning
   2a. Reproductive = cloning to the point of full offspring development.
   2b. Therapeutic = cloning embryo, but removing blastocysts inner cell mass for embryonic stem cells. Aka, no functional offspring results.

Question 10

What is the state of legislation in the US regarding human cloning?

Answer 10

Currently, no federal law prohibits cloning. 7 states ban all forms of cloning, 8 ban only reproductive cloning. Some don’t ban any cloning