Question

10. A genetic analysis of offspring in a cross predicts that there should be a phenotypic ratio of 3:1, but geneticists only see 3 offspring, not 4. What is the explanation for this 11. How does mitochondrial DNA differ from genomic DNA?

Answer 1

Ans1) Monohybrid Cross – The monohydrid crosses are independent of the sex and hence despite having 3 offsprings, the genetic analysis predicts the phenotypic ratio to be 3:1. It is basically mating between two organisms and the organisms have variation in one of the chromosomal level of interest. There are multiple variations governed by two or more genes present in the single locus.

Ans 2)

Mitochondrial DNA	Nuclear DNA
The mitochondrial DNA is present in the mitochondria and circular, double stranded	It is present in the nucleus and is double stranded, linear
It is not enveloped by the nuclear membrane	It is enclosed and enveloped by the nuclear membrane
There are 100 – 1000 copies per somatic cell	There are only 2 copies per somatic cells
The base pair present in one chromosome is around 16,569	The base pair present in 46 chromosomes which is in human is 3.3 billion
There are only 37 genes that are encoded by the mitochondrial DNA	It has nearly 20,000 – 25,000 that encodes the nuclear DNA
The mode of inheritance is only maternal	The mode of inheritance is both maternal and paternal where half comes from male and half from female
The transcription is polycistronic	The transcription is monocistronic