Read the following statements. Statement I: In a typical test cross, an organism showing a dominant phenotype is crossed with the recessive parent. Statement II: The ratio of organisms showing dominant and recessive traits in F1 generation of a test cross indicates that the organism with unknown genotype is homozygous dominant. Choose the correct option.
Statement I is true but Statement II is false
A test cross is a cross between an organism showing the dominant phenotype, whose genotype is unknown, and the homozygous recessive parent. Mendel used it to find out the genotype of a dominant-looking organism.
Statement I — true. In a typical test cross the organism with the dominant phenotype is crossed with the recessive parent, exactly as Mendel described.
Statement II — false. The ratio of the progeny decides the genotype. If dominant and recessive progeny appear in a 1 : 1 ratio, the unknown organism is heterozygous (Tt × tt → 1 Tt : 1 tt). Only when all the progeny show the dominant trait is the unknown organism homozygous dominant (TT × tt → all Tt). So a ratio of dominant and recessive organisms does not indicate homozygous dominance.
Because Statement I holds and Statement II does not, the choices saying both are true, both are false, or only Statement II is true do not fit.
Statement I is true but Statement II is false option is correct.
Similar Questions
In a practical examination, the below given pedigree chart was given as spotter for identification.
The students identified the pedigree chart as ________
Identify the correct order of stages in Human evolution.
a) Homo habilis
b) Homo erectus
c) Australopithecus
d) Neanderthal man
e) Dryopithecus
According to Hugo De Vries, speciation is due to __________.
Select the statement which is ‘NOT’ true about Big Bang Theory.
Arrange the below given steps of DNA fingerprinting in sequence by selecting the appropriate option.
a) Digestion of DNA by restriction endonucleases
b) Autoradiography
c) Blotting of DNA fragments to nitrocellulose membrane
d) Isolation of DNA
e) Separation of DNA fragments by electrophoresis
In a DNA molecule, cytosine is 28%. Calculate the percentage of adenine.
Who amongst the following scientist/s had no contribution in the development of the double-helix model for the structure of DNA?
Thalassemia and Sickle cell anaemia are due to a problem in globin molecule synthesis.
Select the correct statement.
The classical example of point mutation is
The genotypes of husband and wife are IAIB and IAIO. Among the blood groups of their children, how many different genotypes and phenotypes are possible?
Important Questions from Genetics and Evolution
- Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : Forelimbs of human and bats are homologous.
Reason R : Forelimbs of humans and bats have similar anatomical structure.
In the light of the above statements, choose the most appropriate answer from the options given below : - Given below are two statements :
Statement I : Modern *Homo sapiens* arose in Australia and moved across continents.
Statement II : *Homo sapiens* arose around 75000 to 10000 years ago.
In the light of the above statements, choose the most appropriate answer from the options given below : A population of diploid organisms is at Hardy-Weinberg equilibrium. If the frequency of allele A is 0.1, the frequency of AA is ____________ .
Adaptive radiation in placental mammals and Australian Marsupials leading to similarity between distant species is an example of ___________
- Natural selection can lead to
(a) stabilisation
(b) genetic drift
(c) directional change
(d) disruption
Choose the correct answer from the options given below :
