Lethal gene, Biology

LETHAL GENE (2:1 Instead of 1 : 2 : 1 or 3 : 1)

(i)         All the genes present in an organism are not useful, but some of them show harmful effects and sometimes may cause death or lethality. Such factors or genes which cause death or lethality in an organism are called lethal gene or factors.

(ii)         These lethal factors are fortunately present in recessive state and thus cause death only in homozygous condition. In heterozygous condition, they may cause structural changes.

(iii)        Lethal factors were first of all reported in mice body colour by a French geneticist, L. Cuenot (1905). According to him, yellow mice never show true breeding and when yellow mouse is crossed with another yellow mouse, produce yellow and brown in the ratio of 2 : 1 (not 3 : 1). Yellow mouse is never present in homozygous condition.

(iv)        In the following example, 'Y' is a dominant gene for body colour but is recessive for lethality and when recessive genes come in homozygous condition, death is caused (i.e; YY - dies).

1213_lethal genes.png

(v)         Lethal factors in case of plants were reported first of all in Snapdragons (Antirrhinum majus) by E. Baur (1907). (vi) In Snapdragons (Antirrhinum majus), yellow leaved (golden leaved) or 'aurea' variety never breeds true. When aurea variety is crossed with aurea, aurea and green are produced in the ratio of 2 : 1 (not 3 : 1) i.e. aurea is always heterozygous (Gg).

1469_lethal genes1.png

(vii)        Here again 'G' is dominant gene for yellow colour but is simultaneously recessive for lethality and when recessive gene come in homozygous condition, death is caused (i.e; GG - dies). 

Thus lethal factors cause modification of 3 : 1 ratio into 2 : 1.

Posted Date: 10/10/2012 4:35:13 AM | Location : United States







Related Discussions:- Lethal gene, Assignment Help, Ask Question on Lethal gene, Get Answer, Expert's Help, Lethal gene Discussions

Write discussion on Lethal gene
Your posts are moderated
Related Questions
Female Reproductive Tract The female reproductive tract involves the fallopian tubes, uterus and vagina. Look at diagram. You would notice that the ovaries lay one on each si

Diagram of a cell surface membrane.  State the width of a cell surface membrane. (i) On which side of the membrane, shown in Figure, X or Y, is the cytoplasm of the cell?

How are antivenoms produced? Why are antivenoms an example of passive immunization? Antivenoms are getting by the following process: the venom (antigen) is inoculated into othe

what is the classification of protozoa

Explain in detail about the term behavioural neuropsychology Behavioural neuropsychology has been explained as 'the application of behaviour therapy techniques to problems of o

Development Projects - Deforestation The use of science and technology to support the ever- increasing needs of man is termed as development. In the recent years, the human po

Considering the hybridization in a given trait like the color of the hair of a mammalian species (white/black) conditioned by a pair of different alleles under complete dominance (

Types of Ovules Anatropous This is the most common type of ovule in angiosperms in which the ovule undergoes curvature such that the micropylar end comes to lie parallel

Metabolic Processes Living things are complex and yet, the cell is the basic unit of life New cells result of mitosis cell division DNA controls all cell functions

A 21-year-old woman presents with a 3-month history of malaise, joint pain, weight loss, and sporadic fever. Her temperature is 38°C (101°F). The serum antinuclear antibody (ANA) t