Genetics Module

Q 1. If a colorblind woman marries an average-visioned man, their sons will be

1. Three-fourths colorblind and one-fourth normal
2. One-half colorblind and one-half normal
3. All normal visioned
4. All colorblind

Answer: a, Three-fourths colorblind and one-fourth normal
Explanation: Color blindness is an X-linked recessive trait passed down from fathers to their sons. If both father and mother are carriers of the genetic trait (neither being colorblind), then there is a three in four chance that any son born to them will be colorblind.

Q 2. Which of the following is the significance of dominance?

1. organisms with dominant genes have stronger vitality
2. the dominant gene does not express the deleterious mutation;
3. heterosis is due to a dominant gene
4. all of the above

Answer: d, all of the above
Explanation: Dominance is a genetic phenomenon where one gene pair allele suppresses the other allele’s expression, making certain traits more noticeable than others. It means that organisms with dominant genes are more vital, harmful mutations are not expressed due to dominant genes, and heterosis is also due to the dominant gene.

Q 3. An individual’s homozygosity and heterozygosity can be determined by

1. Test cross
2. Back cross
3. Self-fertilization
4. All of the above

Answer: d, All of the above
Explanation: Genetics is complex, but you can quickly determine an individual’s homozygosity and heterozygosity with the right tools. Test cross, Back cross, and Self-fertilization are all techniques that allow for this determination to be made. With Genetics tools, you can quickly and effectively understand the complexity of genetics!

Q 4. The smallest unit of genetic material that produces a phenotypic effect on mutation is:

1. Gene
2. Muton
3. Nucleic acid
4. Recon

Answer: a, Gene
Explanation: A gene is the smallest unit of genetic material that produces phenotypic effects. A gene is a specific sequence of nucleotides in DNA that contains the instructions for synthesizing a particular protein or functional RNA molecule. Modifications can occur within genes, resulting in alterations to the genetic code, leading to changes in the structure or function of the protein or RNA produced. These gene sequence and expression changes can then manifest as a phenotypic effect or trait.

Option b) Muton: The term “muton” refers to a hypothetical unit of mutation proposed in early genetics studies. However, the concept of the muton as a discrete unit of mutation has yet to be widely used or accepted in modern genetics.

Option c) Nucleic acid: Nucleic acids, such as DNA and RNA, are the macromolecules that make up the genetic material in living organisms. While mutations can occur within nucleic acids, the genetic information encoded within genes produces phenotypic effects.

Option d) Recon: The term “recon” is not commonly used in genetics and does not represent the smallest unit of genetic material that produces phenotypic effects on mutation.

Q 5. Farmers planted 200 kernels of corn and produced 140 tall & 40 short plants. The genotypes of these offspring are likely similar :

1. TT, tt
2. TT, Tt, tt
3. TT, Tt
4. Tt, tt

Answer: b, TT, Tt, tt.
Explanation: This type of genetic inheritance follows the laws of Mendelian Genetics, which states that offsprings receive one allele from each parent, possibly having three different genotypes when two parents with different alleles are involved. Therefore, the genotypes of these offspring are TT, Tt, and tt.

Q 6. Types of phenotypes of the F2 generation of dihybrid cross?

1. 4
2. 16
3. 8
4. 9

Answer: b, 16
Explanation: In a dihybrid cross, where two traits controlled by different genes are crossed, the F2 generation can exhibit 16 phenotypes. The F2 generation results from the parental generation’s random assortment and recombination of alleles. There are two possible alleles for each gene; when considering two genes, there are four different allele combinations.

The 16 possible phenotypes arise from the various combinations of these four allele combinations. Each allele combination can result in a distinct phenotype for each trait being considered. By multiplying the number of possible phenotypes for each trait (2 x 2), we get 4 different phenotypes. Multiplying this by the number of possible phenotypes for the other trait (4 x 4), we obtain 16 phenotypes for the F2 generation.

Q 7. Cross XXYy and xxYy yields XxYY: XxYy : Xxyy: xx yy offspring in the ratio of

1. 0 : 3: 1 : 1
2. 1: 2 : 1 : 0
3. 1: 1 : 1: 1
4. 1: 2 : 1: 1

Answer: b, 1: 2 : 1 : 0
Explanation: To determine the ratio of offspring from the cross XXYy and xxYy, we can use a Punnett square to calculate the possible combinations of alleles.

First, let’s write out the gametes for each parent:

Parent 1 (XXYy): XY, Xy

Parent 2 (xxYy): xY xy

Now, let’s construct the Punnett square

From the Punnett square, we can see that the possible genotypes and their corresponding ratios are as follows:

1. XxYY: 1
2. XxYy: 2
3. Xxyy: 1
4. xxyy: 0

Q 8. In the Mirabilis plant, the appearance of the pink hybrid (Rr) between a cross of a red (RR) and white (rr) flower parent indicates

1. Segregation
2. Dominance
3. Incomplete dominance
4. Heterosis

Answer: c, Incomplete dominance
Explanation: Incomplete dominance occurs when the two alleles in a gene are not expressed in the same way, resulting in an intermediate phenotype between those of both parents. In the Mirabilis plant, this is seen in the pink hybrid (Rr) between a cross of a red (RR) and white (rr) flower parent. This indicates incomplete dominance.

Q 9. If only parental combinations in F2 of a dihybrid cross existed, then Mendel might have discovered?

1. Independent assortment
2. Atavism
3. Linkage
4. Repulsion

Answer: c, Linkage
Explanation: Mendel might have discovered the phenomenon of Linkage if there were only parental combinations in F2 of a dihybrid cross. This is when two genes are inherited due to being close to the same chromosome. The other options, Independent Assortment, Atavism, and Repulsion, could not explain the parental combinations in F2.

Q 10. If the distance between the gene on the chromosome is more, then the gene shows

1. less linkage
2. strong linkage
3. weak linkage
4. incomplete linkage

Answer: a, less linkage
Explanation: When the distance between two genes on a chromosome is further apart, then it exhibits less linkage. This decrease in linkage occurs as the amount of recombination between DNA increases and it decreases the likelihood that two linked traits are inherited together.

Q 11. Degeneracy of genetic code is due to

1. functional 61 codons and 20 amino acids
2. functional 64 codons and 20 amino acids
3. functional 20 codons and 20 amino acids
4. functional 20 codons and 61 amino acids

Answer: b, functional 64 codons and 20 amino acids
Explanation: Degeneracy of genetic code is the phenomenon in which more than one codon codes for the same amino acid, and it presents itself due to the fact that there are 64 codons but only 20 amino acids. This allows for multiple codons to code for the same amino acid and results in a certain degree of redundancy.

Q 12. What if the 25th codon (UAU) of the gene encoding a 50 amino acid polypeptide is mutated to UAA?

1. A 24 amino acid polypeptide is formed
2. A 25 amino acid polypeptide is formed
3. A 49 amino acid polypeptide is formed
4. Two polypeptides of 24 and 25 amino acids are formed

Answer: c, A 49 amino acid polypeptide is formed
Explanation: This is because UAA is a “stop codon”, meaning it signals the end of the gene sequence. In this case, the gene sequence ends at the 25th amino acid, resulting in a polypeptide of 49 amino acids.

Q 13. Signaling between cells usually results in the activation of protein

1. Lipases
2. Kinases
3. Proteases
4. Nucleases

Answer: b, Kinase
Explanation: Signaling between cells often involves the activation of proteins through phosphorylation, which is the addition of phosphate groups to specific amino acids within the protein. This phosphorylation event is catalyzed by enzymes called kinases.

Kinases play a crucial role in signal transduction pathways by transferring phosphate groups from ATP (adenosine triphosphate) to target proteins, which can modify their structure, activity, or cellular localization. This phosphorylation can activate or deactivate the target proteins, allowing for the transmission and amplification of signals within the cell.

Q 14. Cystic fibrosis is

1. Autosomal dominant disorder
2. Sex-linked recessive disorder
3. Sex-linked dominant disorder
4. Autosomal recessive disorder

Answer: d, Autosomal recessive disorder
Explanation: Cystic fibrosis is an autosomal recessive disorder. This means that both parents must carry a defective copy of the gene for it to be passed on to their child. It cannot be passed on by either sex alone but can be inherited from either parent or both parents.

Q 15. What if Mendel discovered only the parental combinations in F2 of a dihybrid cross?

1. Independent assortment
2. Atavism
3. Linkage
4. Repulsion

Answer: c, Linkage
Explanation: Mendel might have discovered Linkage if there were only parental combinations in F2 of a dihybrid cross. In genetics, linkage is the preferential association between alleles at two or more loci on the same chromosome and is responsible for some non-random patterns of inheritance.