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Correct choice is (a) Genes involved in QUANTITATIVE inheritance

For EXPLANATION I would say: Genes which are involved in quantitative inheritance are CALLED as POLYGENES. In quantitative inheritance, each dominant allele expresses itself as a part of functional polypeptide and the full trait is shown when all the dominant alleles are PRESENT in an organism.

Correct answer is (a) Contrasting traits

For explanation I WOULD say: Through the experiments of pea CONDUCTED by Mendel, he DESCRIBED DISTINCT contrasting traits such as flower colour which are either purple or white.

Correct CHOICE is (d) Traits CONTROLLED by THREE or more genes

For explanation I would say: Traits are the FEATURE of a character by which we can distinguish organisms. Traits which are generally controlled by three or more genes are known as polygenic traits.

Correct option is (a) Human Genome PROJECT

The best I can explain: HGP is an ACRONYM for Human Genome Project. It was a huge initiative that ACHIEVED in SUCCESSFULLY obtaining the human genome SEQUENCE.

The CORRECT option is (d) Alfred

Easy explanation: Alfred was Morgan’s student. He USED the methodology of Morgan to obtain RECOMBINATION FREQUENCIES of GENES and thus map them on the chromosomes.

Right answer is (a) high

To explain I would say: Loosely LINKED GENES are located very far from each other. That ALLOWS recombining FREQUENTLY. Thus, they exhibit high recombination.

The correct choice is (C) low

Explanation: Tightly linked GENES are located very close to each other. This renders them UNABLE to recombine FREQUENTLY. Thus, they EXHIBIT low recombination.

Right choice is (B) Recombination frequency

Explanation: Recombination frequency is a simple measure that can be obtained by analyzing the progeny of the cross. It can then be used to DETERMINE the linkage, genetic MAPS, and GENE density.

Correct answer is (a) True

The best explanation: Genes located on different chromosomes are weakly linked. This ALLOWS them to recombine more frequently. Linkage is inversely related to recombination. Genes are located close to each other have low CHANCES of recombination, and thus have high linkage. Genes on different chromosomes are far from each other, hence they have ALMOST no linkage, hence having higher chances of undergoing recombination.

The correct OPTION is (b) Recombination

To ELABORATE: Recombination LEADS to combinations of genes. Hence leads to newer PHENOTYPES. The parental phenotypes occur WITHOUT recombination hence are more frequently observed in the progeny. Recombination events are rare and hence the non-parental phenotypes are rare.

The correct option is (a) X CHROMOSOME

To explain I would say: The genes were located on X-chromosome. These are called sex-linked genes because their EXPRESSION depends on the sex of the FLY. The X chromosome is present in copies of two in females, but the MALES have only one copy of X. Thus, a recessive mutant might remain SUPPRESSED in females, but the males will always exhibit the phenotype.

The CORRECT answer is (a) LINKAGE

To explain I would SAY: Linkage is the phenomenon of the PHYSICAL association of genes that are LOCATED on the same chromosome. This leads to fewer chances of genes undergoing independent segregation.

The correct CHOICE is (a) True

Easy EXPLANATION: For genes that are LOCATED on the same chromosome, segregation is WEAK as they are linked. This leads to more chances of parental combinations than of the non-parental ones.

Right choice is (b) Genes do not segregate independently

To elaborate: If the segregation law was to HOLD, the expected phenotypic ratio of F2 was 9:3:3:1. HOWEVER, Morgan saw a deviation from this ratio. This implied that the genes do not segregate independently.

The correct option is (a) Yellow-bodied, white-eyed FEMALES with brown-bodied, red-eyed males

For explanation I WOULD say: Morgan used DROSOPHILA as a genetic model to visualize the changes in the CHROMOSOMAL patterns and explain the observations of MENDEL. For this, he performed a dihybrid cross of yellow-bodied, white-eyed females with brown-bodied, red-eyed males.

The correct answer is (B) Drosophila melanogaster

Best explanation: Drosophila melanogaster are the fruit FLIES. They are small and hence can be easily CULTURED in lab SETTINGS on a synthetic medium.

Right option is (b) Violent organisms

Easiest explanation: The fruit flies are tiny and can be grown in lab SETTINGS. They have a SHORTER lifespan and produce MANY progenies after mating. This MAKES them a suitable model ORGANISM.

The correct OPTION is (a) Morgan

Easiest EXPLANATION: THOMAS Hunt Morgan and colleagues used fruit flies as their model organism. Many studies were done that VERIFIED the chromosomal THEORY of inheritance.

The correct ANSWER is (b) DROSOPHILA melanogaster

To elaborate: Thomas Hunt MORGAN, along with his colleagues, led to the ESTABLISHMENT of fruit flies Drosophila melanogaster as the model organism. It has been used for many STUDIES that have potential applications to human society.

The correct OPTION is (b) Drosophila melanogaster

For explanation: Drosophila melanogaster was used to verify the CHROMOSOMAL theory of inheritance. This was done by THOMAS Hunt Morgan and his colleagues. The reason for this MODEL organism OWES to its polytene chromosomes.

The correct option is (c) Chromosomes SEGREGATE independently of each other

Easy explanation: The chromosomal theory of inheritance was devised by the observations of the movements of chromosomes during the process of MEIOSIS. ACCORDING to this theory and the EXPERIMENTS that VALIDATE it, the chromosomes segregate independently of each other.

The correct option is (a) MORGAN

The explanation is: Morgan, along with his STUDENTS and colleagues, LED to the setting up of FRUIT flies as the model organism. Today fruit fly is used WIDELY for many studies.

Correct answer is (a) CHROMOSOMAL THEORY of INHERITANCE

To explain: Sutton and BOVERI were the key players in the world of biology during the decade of 1900-1910. They observed chromosome movements and studied Mendel’s experiments. BASED on these, they devised the chromosomal theory of inheritance.

Correct CHOICE is (C) SUTTON and Boveri

For explanation: Sutton and Boveri were inspired by Mendel’s studies. With the advent of microscopy, they could OBSERVE the CHROMOSOMAL movements during meiosis. Both of these led them to devise the chromosomal theory of inheritance.

Right option is (a) Chromosomal theory of inheritance

To explain: The chromosomal theory of inheritance was STATED by Sutton and BOVERI. It TALKS about the movement of chromosomal pairs independent of each other to reach the METAPHASE plate during Meiosis I.

The correct answer is (c) Sutton and Boveri

Explanation: Sutton and Boveri had STUDIED the segregation of chromosomes very closely by staining the cells and then DEVELOPING a differential staining approach to visualize the pairs of chromosomes. To their SURPRISE, this was very similar to the expectation of Mendel’s factors. Hence they made the conclusion that INDEPENDENT SEPARATION of chromosomes should lead to independent segregation of factors.

Right option is (b) Bivalent

For explanation I WOULD say: The pair of CHROMOSOMES that line up during meiosis has two COPIES of each homologous CHROMOSOME. Hence it is called a bivalent.

Correct option is (b) False

Explanation: The variation occurs DUE to the independent segregation of CHROMOSOMES during the Metaphase I. The Metaphase II plate does not lead to variation because all possible pairs are IDENTICAL as they contain COPIES of the same chromatid.

The CORRECT ANSWER is (a) METAPHASE I

Explanation: The INDEPENDENT segregation of CHROMOSOME pairs occurs during the Metaphase I. This leads to the variations in the daughter cells or germ cells.

Right answer is (a) CHROMATID

For explanation I would SAY: The chromosomes duplicate during the G2 phase of the cell cycle. Each copy of the chromosome is IDENTICAL and is hence called a chromatid. The G2 phase is followed by M phase or MEIOTIC phase, where the chromatids align together at the metaphase plate followed by segregation during the anaphase.

Right option is (a) True

For explanation I would say: The Metaphase I involve the independent SEGREGATION of the chromosomal PAIRS by their independent arrangement at the Metaphase plate. This led to the VARIATIONS observed in the daughter cells.

Right option is (b) False

The best explanation: The ALIGNMENT of chromosomal pairs is INDEPENDENT of each other. This is what leads to the statement of the chromosomal BASIS of inheritance.

Correct choice is (d) 4 GIGA base pairs

Explanation: The cell starts with two copies of each chromosome during the G1 phase. G2 phase WITNESSES DNA DUPLICATION. However, by the end of Meiosis II, cell splits into four, and each germ cell receives a single COPY of each chromosome. Thus, the DNA content at the end of meiosis WOULD be half what it was at the time of onset.

Right CHOICE is (d) 4 GIGA base pairs

Best EXPLANATION: Cells undergo DNA duplication during G2 phase. This is split at the end of Meiosis I. However, until the Telophase I, the CELL retains twice the DNA content as at the onset of G1.

Right answer is (b) 2 Giga base pairs

To explain: Cell at G1 phase has a PAIR of chromosomes. By the end of ANAPHASE II, it still has a pair of chromosomes. Hence the DNA CONTENT would be ALMOST the same as at the time of G1.

Correct choice is (c) Meiosis II Anaphase

To explain I WOULD say: Meiosis takes place in TWO PHASES and involves the separation of chromosomes twice. The SECOND segregation occurs in the Anaphase of Meiosis II.

Right answer is (a) Meiosis I Anaphase

The explanation is: The segregation of chromosomes OCCURS when the SPINDLE fibers pull the fibers pull the chromosomes to the poles and AWAY from the METAPHASE plate. The first such segregation occurs during meiosis I Anaphase.

Correct answer is (a) HOMOLOGOUS CHROMOSOMES

To explain: The ALLELES of a gene compete or support each other for expression. Hence, they have to be present at homologous sites and on homologous chromosomes.

Right ANSWER is (b) G2 PHASE

Explanation: G2 phase is the biosynthetically active phase. During this phase, a lot of energy is spent by the cell to GROW and DUPLICATE its genomic content.

The correct choice is (d) in pairs, in pairs

The best I can explain: A DIPLOID CELL has double the set of chromosomal content. Hence there are two copies for each chromosome present. These are called homologous chromosomes. Now, GENES are FRAGMENTS of DNA present on the chromosomes. Hence they also occur in pairs, with one gene present on each homologous chromosomes.

Right OPTION is (B) Meiosis

The EXPLANATION: During the process of meiosis, each DAUGHTER cell gets only half the original chromosomal CONTENT. Hence it is called the reduction division.