Tag: classical genetics
Questions Related to classical genetics
Allelic sequence variations where more than one variant (allele) at a locus in a human population is with a frequency greater than 0.01 is referred to as
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Incomplete dominance
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Multiple allelism
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SNP
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EST
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DNA polymorphism
Incomplete dominance means that one allele for a trait is not completely dominant over the other one and thus the heterozygous genotype shows a combination of dominant and recessive phenotypes. Mirabilis plant shows incomplete dominance of flower colour. Multiple allelism is a condition when more than two alleles of a gene govern the trait. Human blood group inheritance is the example of multiple alleles. It is governed by three alleles namely I$^{A}$, I$^{B}$ and I$^{A}$ and I$^{B}$ show codominance while allele i is recessive to both "I$^{A}$" and "I$^{B}$". This gives total six genotypes and four phenotypes- A (I$^{A}$ I$^{A}$ and I$^{A}$i), B (I$^{B}$ I$^{B}$ and I$^{B}$i), AB (I$^{A}$ I$^{B}$) and O (ii).
coding region of a gene and is used to identify the full-length genes in gene mapping. It is derived from cDNA, i.e., DNA formed using RNA template via reverse transcription.
DNA polymorphism can be defined as a condition where more than one different normal nucleotide sequences can exist at the same locus in DNA. These two different alleles are the product of single base pair mutation, deletions, insertions etc.
Incomplete dominance was first discovered by
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Mendel
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Hugo de Vries
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Carl Correns
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Tschermak
- Gregor Mendel was the founder of modern genetics. He performed experiments of on pea plant and established many rules of heredity, now referred to as the laws of Mendelian inheritance.
- Hugo de Vries gave the concept of genes, rediscovered laws of heredity, introduced the term mutation and gave the mutation theory of evolution.
- Carl Correns is known for his independent discovery of the principles of heredity and also discovered non-mendelian inheritance like cytoplasmic inheritance or cytoplasmic inheritance.
- Tschermark developed several new disease-resistant crops. Along with Vries and Correns, he discovered Gregor's work.
Mendel's experiments could not explain
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Incomplete dominance
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Segregation
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Recessiveness
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Dominance
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Independent assortment
Mirabilis jalapa shows
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Codominance
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Incomplete dominance
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Dominance
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Complementary genes
Incomplete dominance is the condition when none of the factors of a gene is dominant; the phenotype of a heterozygous dominant individual is a blend of dominant and recessive traits. A monohybrid cross between two pure varieties of Mirabilis jalapa with red (RR) and white (rr) flowers gives red, pink and white colored flowers in 1:2:1 phenotypic ratio in $F _2$ generation. This is because the red color exhibits incomplete dominance over white color and the heterozygous dominant genotype (Rr) produces different phenotype from homozygous dominant (RR). Flower color in Mirabilis jalapa is governed by a single gene. Thus, the correct answer is option B.
A red snapdragon flower is crossed with a white snapdragon flower, and all the resulting flowers from the cross are pink. Which type of inheritance is occurring here?
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Incomplete dominance
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Codominance
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Sex-linked inheritance
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Pleiotropy
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Polygenic inheritance
Incomplete dominance is also called
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Intermediate inheritance
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Blending inheritance
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Partial dominance
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All the above
Mendel did not propose
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Dominance
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Incomplete dominance
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Segregation
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Independent assortment
A.Law of dominance – When two contrasting alleles for a character come together in an organism, only one is expressed and another one is not expressed. Expressed character is called Dominant character and the character which is not expressed is called Recessive character
B.Incomplete dominance – Expression of new phenotypes in the progeny, other than the parents is called Incomplete dominance
C.Segregation – This law states both parental alleles of F1 generation separate and are expressed phenotypically in F2 generation
D.Independent assortment – When a cross is made between two individuals different from each other in two or more characters, then the inheritance of one character is independence of the inheritance of another character
So, the correct answer is ‘Incomplete dominance’
Phenotypic and genotypic ratio in $F _2$ generation in incomplete dominance is
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1 : 2 : 1 and 1 : 2 : 1
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3 : 1 and 1 : 2 : 1
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9 : 6 and 3 : 1
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9 : 3 : 3 : 1 and 1 : 2 : 1 : 4 : 1 : 1 : 2 : 1 : 2 : 1.
Appearance of new phenotypes or intermediate phenotypes, other than parental phenotypes in progeny is incomplete dominance. In this, In the F2 generation, 1 red flowered plants(RR), two pink flowered plants(Rr), 1 white flowered plants(rr) are formed. So, the phenotypic and genotypic ratio is 1:2:1.
So, the correct option is ‘1:2:1 and 1:2:1’.
A plant having 24 cm long internodes is crossed with a plant having 12 cm long internodes. The hybrids have 18 cm long internodes due to
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Multiple allelism
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Complete dominance
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Recessive dominance
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Incomplete dominance
Appearance of new phenotypes or intermediate phenotypes, other than parental phenotypes in progeny is incomplete dominance. A plant having 24cm long internodes is crossed with plant having 12cm long internodes. In the hybrids 18cm long internodes appear. It is due to blending of characters. So, it is called Incomplete dominance or blending inheritance.
So, the correct option is ‘Incomplete dominance’.
Which one is exception to Mendel's principle of dominance?
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Wild Pea
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Mirabilis
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Garden Pea
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Maize
Gregor Johann Mendel, an Austrian Monk, discovered the principles of heredity through the experiments on the pea plant. Mendel conducted hybridization experiments on garden peas for seven years and proposed the laws of inheritance in living organisms. They are Law of dominance, Law of segregation, Law of Independent assortment. These laws are exceptional in some cases like incomplete dominance, co-dominance, etc.
So, the correct option is ‘Mirabilis’.