12-Bio-Botany-Unit-III Cell Biology And Genetics

2.

Who had first proved that the genes are carried by the chromosome?

Bridges
Waldeyer
Balbiani
Flemming

Correct Answer

A. Bridges

Explanation

Bridges is the correct answer because he was the first to provide experimental evidence that genes are carried by the chromosome.

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3.

The coupling test cross ratio is

7:1:1:7
1:7:7:1
1:1:1:1
9:3:3:1

Correct Answer

A. 7:1:1:7

Explanation

The given answer, 7:1:1:7, represents a coupling test cross ratio. This ratio indicates the relative frequencies of different genotypes in a test cross between two heterozygous individuals. The presence of the same alleles on opposite chromosomes (7:7) suggests that these alleles are tightly linked and likely to be inherited together. The presence of a different allele (1) in the middle suggests recombination has occurred. This ratio suggests that recombination is less likely to happen between the outer alleles (7) and more likely to occur between the middle allele (1) and the outer alleles.

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4.

Recombination of chromosome takes place in _____ stage of prophase I of meiosis.

Pachytene
Leptotene
Zygotene
Diplotene

Correct Answer

A. Pachytene

Explanation

During the pachytene stage of prophase I of meiosis, recombination of chromosomes occurs. This is when homologous chromosomes pair up and exchange genetic material through a process called crossing over. This exchange of genetic material leads to genetic diversity in offspring. Therefore, pachytene is the correct stage for recombination to take place.

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1

5.

Hugo de Vries first used the term mutation based on his observation on

Oenothera lamarckiana
Sorghum
Neurospora
Cicer gigas

Correct Answer

A. Oenothera lamarckiana

Explanation

Hugo de Vries first used the term mutation based on his observation on Oenothera lamarckiana.

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6.

Biochemical mutants of _____ failed to synthesize certain amino acids.

Neurospora
Sorghum
Cicer arietinum
Cicer gigas

Correct Answer

A. Neurospora

Explanation

Neurospora is a genus of fungi that is commonly used in genetic research. Biochemical mutants of Neurospora have been extensively studied and it has been observed that these mutants are unable to synthesize certain amino acids. This suggests that Neurospora plays a crucial role in the biosynthesis of amino acids.

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7.

Nullisomy is represented by

2n – 2
2n – 1
2n + 1
2n + 2

Correct Answer

A. 2n – 2

Explanation

Nullisomy is a type of aneuploidy where there is a loss of both homologous chromosomes of a pair, resulting in a total chromosome number that is two less than the diploid number (2n). Therefore, the correct answer is 2n - 2.

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8.

The gametes of Drosophila melanogaster carry

Four chromosomes
Three chromosomes
Seven chromosomes
Eight chromosomes

Correct Answer

A. Four chromosomes

Explanation

Drosophila melanogaster, commonly known as fruit flies, have four chromosomes in their gametes. Chromosomes are the structures that contain the genetic material of an organism. In fruit flies, there are four distinct chromosomes that carry the genes responsible for various traits and characteristics. These chromosomes are passed on to the offspring through the gametes, which are the reproductive cells. Therefore, the correct answer is four chromosomes.

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9.

Double helix DNA model was proposed by _____

Watson and Crick
O.T. Avery et al
Griffith
Stinberg

Correct Answer

A. Watson and Crick

Explanation

Watson and Crick proposed the double helix DNA model. They are known for their discovery of the structure of DNA, which they published in 1953. Their model explained how DNA is composed of two strands that are twisted together in a helical shape, forming a double helix structure. This model revolutionized our understanding of genetics and laid the foundation for further research in the field.

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10.

The width of DNA molecule is

20 Å
18 Å
34 Å
35 Å

Correct Answer

A. 20 Å

Explanation

The width of a DNA molecule is 20 Å. This measurement refers to the distance between the two strands of the DNA double helix. The width of DNA is important because it determines the spacing between the nucleotide bases, which in turn affects the overall structure and stability of the molecule. The correct answer is 20 Å.

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11.

RNA is universally present in all organisms except in _____

DNA viruses
TMV
Bacteria
Algae

Correct Answer

A. DNA viruses

Explanation

RNA is universally present in all organisms except in DNA viruses. This is because DNA viruses replicate their genetic material using a DNA-dependent DNA polymerase, which means they do not require RNA for replication. In contrast, all other organisms, including bacteria, algae, and TMV (Tobacco mosaic virus), use RNA in various cellular processes such as protein synthesis and gene regulation.

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12.

MRNA is about _____ of the RNA content of the cell

3 - 5%
10 - 20%
5 - 10%
20 - 30%

Correct Answer

A. 3 - 5%

Explanation

mRNA, or messenger RNA, is a type of RNA molecule that carries genetic information from the DNA to the ribosomes, where it is used as a template for protein synthesis. It is a relatively small portion of the total RNA content in the cell. Therefore, the correct answer is 3 - 5%, indicating that mRNA makes up only a small fraction of the RNA content in the cell.

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13.

In bacterial cell, there are more than _____ tRNAs

70
200
300
400

Correct Answer

A. 70

Explanation

In bacterial cells, there are more than 70 tRNAs. These tRNAs are responsible for carrying specific amino acids to the ribosomes during protein synthesis. Each tRNA molecule has a specific anticodon sequence that matches with a specific codon on the mRNA. This allows the tRNA to bring the correct amino acid to the growing polypeptide chain. The large number of tRNAs in bacterial cells ensures that there is a wide range of amino acids available for protein synthesis, allowing for the production of diverse proteins necessary for the cell's functioning.

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12-bio-botany-unit-III Cell Biology And Genetics

The term chromosome was introduced by

Quiz Preview

Who had first proved that the genes are carried by the chromosome?

The coupling test cross ratio is

Recombination of chromosome takes place in _____ stage of prophase I of meiosis.

Hugo de Vries first used the term mutation based on his observation on

Biochemical mutants of _____ failed to synthesize certain amino acids.

Nullisomy is represented by

The gametes of Drosophila melanogaster carry

Double helix DNA model was proposed by _____

The width of DNA molecule is

RNA is universally present in all organisms except in _____

MRNA is about _____ of the RNA content of the cell

In bacterial cell, there are more than _____ tRNAs