An organism having a diploid number of 12 forms gametes having 2. a. b. C. d. e.

Question

An organism having a diploid number of 12 forms gametes having 2. a. b. C. d. e. 6 replicated chromosomes 3 homologous pairs 6 unreplicated chromosomes 12 sister chromatids 12 unreplicated chromosomes 3. Crossing over occurs a. b. c. d. During Prophase ll Only between sister chromatids Between homologous chromosomes Prior to DNA replication 4. Which of the following represents chromosome number before and after the process of meiosis? b. n 2n 5. Mendel discovered principles of inheritance because he Observed simultaneously all of the many characteristics in which the parents differed a. thoroughly blended in the offspring Ignored all characteristics except a few markedly contrasting ones in which he studied Studied only the offspring obtained from a single mating c. d. 6. Why did Mendel continue some of his experiments to the F2 or F3 generation? a. b. c. d. e. To obtain a larger number of offspring on which to base statistics To observe whether or not a recessive trait would reappear To observe whether or not the dominant trait would reappear To distinguish which alleles were segregating To be able to describe the frequency of recombination 7. How many unique gametes could be produced through independent assortment by an individual with t genotype AABbCCDd? An example of alleles is: Which of the following represents a test-cross? Which blood type would not be possible of a type AB mother and type A father? b.4 C. d. 16 a. AB and Tt b. TT and Tt c. T and t d. X and Y a. Txt b.AaxAa d. SsTt x Sstt a. b, A . d. AB

Explanation / Answer

2. Option c - 6 unreplicated chromosomes

Explanation: Organism has diploid number 12. That means 2n=12. By solving we get n=6. This represents 6 haploid. By definition, a gamete is a mature haploid male or female germ cell which has unreplicated chromosome. So, the correct answer is 6 unreplicated chromosomes

3. Option c - between homologous chromosomes.

Explanation: crossing over is a process in which two homologous chromosomes exchange their chromatids during prophase I of meiosis. This results in variation.

4. Option c - 2n ---> n

Explanation: Meiosis is also called as a reductional division. Let us take an example of human chromosomes. The diploid number 2n in humans is 46 (2n=46). During meiosis, 2n transforms to n. That means in meiosis, the chromosome number reduces by two steps (Meiosis I and Meiosis II). Hence, before meiosis 2n=46 and after meiosis n = 23. This generally takes place in germ cells.

5. Option a - Observed simultaneously all of the many characteristics in which the parents differed

Explanation: Mendel thoroughly studied all the characters by conducting monohybrid and dihybrid crosses. With these experiments, he was able to discover the principle of inheritance.

6. Option b - To observe whether or not a recessive trait would reappear

Explanation: Mendel thought that after several generations, recessive traits may disappear due to the occurrence dominant trait. But in the F2 generation, he was able to observe the recessive trait. He further continued the experiment to F3 generation to study the appearance of a recessive trait.

7. Option b - 4

Explanation: Formula used for this calculation is 2 number of heterozygous genes . In the given problem follwing homozygous and heterozygous genes are observed:

AA, CC = Homozygous, Bb, Dd = Heterozygous

So, 2 number of heterozygous genes = 22 = 4

8. Option c - T and t

Explanation: Alleles are always represented with single alphabets. Here T is a dominant allele and t is a recessive allele.

9. Option c - RR x rr

Explanation: Test cross is a cross between an unknown genotype and a homozygous recessive genotype. Here RR is crossed with homozygous recessive rr genotype. Hence, this is a test cross.

10. Option a - O

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