Question

1. How can just paternal or maternal traits be expressed in offspring and how can some "acquired traits" be passed on to offspring?​

2. How can identical twins have identical genomes but different phenotypes (hair color, eye color, height)?​

3. Tell me everything about the composition of a nucleosome. I want exact names and numbers when possible.​

4. Define, compare and contrast heterochromatin and euchromatin and how they relate to gene expression

5. Discuss the relationship between 5 methyl-cytosine and 5 hydroxymethyl-cytosine, mention enzymes responsible for their placement and how each modification affects gene expression.

Answer 1

Ans1) Paternal or maternal traits can be passed on to the offspring with help of DNA which is a genetic material. The offspring has similar traits to parents due to inherited DNA. However, the acquired traits from mother or father can be passed on to the offspring with help of small RNAs. The acquired traits can also be inherited.

Ans 2) The identical twins inherit their genome or genotypic composition from the parents and hence the genotypic characteristics is same. Since the DNA and genes are transferred from parents to both the identical twins, genotypic similarities remain. However, there are phenotypic differences in genetically identical organisms. Such variation has been result of multiple environmental effects. It is found that the environment factors have a massive role to play when it comes to getting different phenotypes.

Ans c)The nucleosome is the basic DNA packaging unit that consists of a DNA segment that is wound around the histone protein cores. The DNA is wrapped around the histone protein. The core of the nucleosome consist total of 146 base pairs of DNA that is wrapped around a histone octamers. The octamer consists of 2 copies each of the histone proteins which are H2A, H2B, H3 and H4. The linker DNA helps in connecting the core particles.

Ans 4) Contrast between Euchromatin and heterochromatin

Euchromatin	Heterochromatin
The fibres of the euchromatin are coiled loosely and stain deeply during the divisional cycle.	The fibres of the heterochromatin are folded very tightly but the staining is deeper during the interphase.
The region of the euchromatin is mostly active with unique DNA. It replicates mostly during “S” phase.	The region of the heterochromatin consist not only unique DNA. It mostly replicates during onset of divisional cycle.
It is able to synthesize mRNA in-vitro.	It is not able to synthesize mRNA in-vitro.
The phenotype might be affected as it leads to addition or loss of region.	The phenotype is mostly not affected due to addition or loss of this region.
The region is not sticky and hence it is easy to identify.	The region is mostly sticky and at times difficult to identify.
When it comes to temperature, age or sex, euchromatin is less affected.	When it comes to temperature, age or sex, heterochromatin is more affected.
The frequency of cross-over is more.	The frequency of cross over is less.