A certain plant homozygous for yellow seeds and red flowers was crossed with a plant homozygous for green seeds and white flowers. The plants had yellow seeds and pink flowers. The plants were selfed to get progeny. Assuming independent assortment of the two characters, how many phenotypic categories are expected for these characters in the generation? [2023]
9
16
4
6
(4)
When the plant homozygous for yellow seeds and red flowers (YYRR) was crossed with a plant homozygous for green seeds and white flowers (yyrr), plants produced with yellow seeds and pink flowers. This means inheritance of seed colour shows complete dominance while inheritance of flower colour shows incomplete dominance due to blending of two alleles. This can be shown as follows:
[IMAGE 19]
Phenotypic Yellow seed : Yellow : Yellow : Green : Green : Green
Ratio Red flower Pink White Red Pink White
3 : 6 : 3 : 1 : 2 : 1
Therefore, six phenotypic categories are obtained in the generation.
Match List-I with List-II. [2023]
| List I (Type of cross) | List II (Phenotypic ratio) | ||
| (A) | Monohybrid cross | (I) | 1 : 1 |
| (B) | Dihybrid cross | (II) | 1 : 2 : 1 |
| (C) | Incomplete dominance | (III) | 3 : 1 |
| (D) | Test cross | (IV) | 9 : 3 : 3 : 1 |
Choose the correct answer from the options given below:
(A)-(III), (B)-(IV), (C)-(II), (D)-(I)
(A)-(II), (B)-(IV), (C)-(III), (D)-(I)
(A)-(II), (B)-(III), (C)-(IV), (D)-(I)
(A)-(IV), (B)-(III), (C)-(I), (D)-(II)
Frequency of recombination between gene pairs on same chromosome as a measure of the distance between genes to map their position on chromosome, was used for the first time by [2023]
Alfred Sturtevant
Henking
Thomas Hunt Morgan
Sutton and Boveri
(1)
Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosomes as a measure of the distance between genes and ‘mapped’ their position on the chromosome.
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). [2022]
Assertion (A): Mendel’s law of independent assortment does not hold good for the genes that are located closely on the same chromosome.
Reason (R): Closely located genes assort independently.
In the light of the above statements, choose the correct answer from the options given below:
Both (A) and (R) are correct and (R) is the correct explanation of (A)
Both (A) and (R) are correct but (R) is not the correct explanation of (A)
(A) is correct but (R) is not correct
(A) is not correct but (R) is correct
(3)
The law of independent assortment is applicable to only those factors or genes which are either located distantly on the same chromosome or occur on different chromosomes.
The recombination frequency between the genes a & c is 5%, b & c is 15%, b & d is 9%, a & b is 20%, c & d is 24% and a & d is 29%. What will be the sequence of these genes on a linear chromosome? [2022]
a, d, b, c
d, b, a, c
a, b, c, d
a, c, b, d
(4)
[IMAGE 20]
Experimental verification of the chromosomal theory of inheritance was done by [2020]
Mendel
Sutton
Boveri
Morgan
(4)
Sutton and Boveri proposed the chromosomal theory of inheritance but its experimental verification was done by Thomas Hunt Morgan.
What map unit (centimorgan) is adopted in the construction of genetic maps? [2019]
A unit of distance between genes on chromosomes, representing 50% cross over.
A unit of distance between two expressed genes, representing 10% cross over.
A unit of distance between two expressed genes, representing 100% cross over.
A unit of distance between genes on chromosomes, representing 1% cross over.
(4)
Genetic map is a linear graphic representation of the sequence and relative distance of various genes present in a chromosome. 1% crossing over between two linked genes is known as 1 map unit or centiMorgan (cM).
The frequency of recombination between gene present on the same chromosome as a measure of the distance between genes was explained by [2019]
Sutton Boveri
T.H. Morgan
Gregor J. Mendel
Alfred Sturtevant
(4)
T.H. Morgan coined the term linkage to describe the physical association of genes on chromosome and term recombination to describe the generation of non-parental gene combinations. Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes.
The mechanism that causes a gene to move from one linkage group to another is called [2016]
inversion
duplication
translocation
crossing-over
(3)
Translocation is a chromosomal abnormality caused by rearrangement of parts between non-homologous chromosomes. It may cause a gene to move from one linkage group to another.
In a test cross involving dihybrid flies, more parental-type offspring were produced than the recombinant-type offspring. This indicates [2016]
the two genes are linked and present on the same chromosome
both of the characters are controlled by more than one gene
the two genes are located on two different chromosomes
chromosomes failed to separate during meiosis
(1)
If in a dihybrid test cross more parental combinations appear as compared to the recombinants in generation, then it is indicative of involvement of linkage. Linkage is the tendency of two different genes on the same chromosome to remain together during the separation of homologous chromosomes at meiosis. During complete linkage no recombinants are formed whereas in incomplete linkage few recombinants are produced along with parental combinations.
