Genetics Q&A – Part 2

9. Are there any exceptions to the Mendel’s first law of genetics?
Yes, an exception to the Mendel’s first law of genetics happens in case of gene mutation, which occurs when a base pairs’ sequence gets repaired into a different sequence, after damage caused to the chromosome at the site of gene’s location. Gene mutation may not necessarily be disadvantageous as a little change or mistake in the gene structure can provide for other means through which the offspring may differ from its parent generation. However, it’s a completely different matter when it comes to lethal mutations. Herein, the gene is unable to duplicate exactly and cannot function properly, leading to the death of the animal.

10. Are there any exceptions to the Mendel’s second law of genetics?
Yes, linkage which refers to 2 gene pairs present on the same chromosome, and hence are not independent of each other, is the exception to Mendel’s second law of genetics.

11. How are sex-limited and sex-linked genes different from each other?
The sex-linked genes are carried by the sex chromosomes. Furthermore, the X chromosome has more genes compared to the Y chromosome and therefore when it comes to the sex-linked genes, they’re most likely to be found on the X chromosome. Haemophilia is one major disease that is hugely impacted by the sex-linked genes.
On the other hand, sex-limited genes are the ones which find expression only in either of the sex, for instance the ones associated with milk production. Although this gene is present in both female and male, it only find expression in the female body.

12. What are the difference/s between a phenotype and a genotype?
Genotype refers to the genetic constitution received by an animal from his/her parents. On the other hand, phenotype refers to an animal’s outward physical appearance, for instance the coat or color type. The phenotype may differ from the genotype because of the recessive genes’ presence.

13. What does multifactorial inheritance mean?
Multifactorial inheritance is the term used for describing a characteristic that is influenced by many genes, instead of one single gene or its alleles. Hip dysplasia is a well-known example of multifactorial inheritance wherein several genes interact with the environment as well as between themselves.

14. What is outbreeding?
It is the term used for the process of breeding animals which are less closely related to each other, however, aren’t picked at random. Outbreeding leads to introduction of new genes into the population and thus increases heterozygosity. It also masks the possible effects of recessive genes, leading to the production of better offspring, as the undesirable recessive genes don’t find any means of expression.

15. Is there any disadvantage of outbreeding?
Yes. The outcross’ offspring will cease to breed true, as they’ll be heterozygous for their alleles (instead of being homozygous).

16. What’s meant by a hybrid?
A hybrid results due to cross conveying of a superiority on the heterozygote. There is a specific increase in vigor if the parents originate from different species or strains.

17. How are inherited and congenital defects different?
Congenital defects are from the time of birth and they may occur either because of environmental factors or are inherited. On the other hand, inherited defects may not become evident for some time, as the animal grows. For instance, a cleft palate is a kind of congenital defect.

18. What is epistasis?
Epistasis is the term used for describing the suppressive effect displayed by some genes, on the other genes which aren’t their alleles. You can see it in case of albino animals that are homozygous for recessive gene c, thus preventing the coat color from finding expression. On the other hand, a cc animal turns out to be albino regardless of any coat color genes present in it.