Key Concepts & Solved MCQs on Chromosomal Theory of Inheritance
The speculation that chromosomes could be the key to understanding heredity has led several scientists to review Mendel's publications and re - evaluate his model in terms of chromosome behavior during mitosis and meiosis. In 1902 Theodor Boveri found that there is no proper embryonic creation of sea urchins unless there are chromosomes. That same year, during meiosis, Walter Sutton found the chromosomes were divided into daughter cells. These findings together led to the development of the Chromosomal Heritage Theory, which established chromosomes as the genetic material responsible for Mendelian inheritance.
The chromosomal basis of inheritance theory was consistent with the laws of Mendel, and supported by the following observations:
Homologous chromosome pairs migrate during meiosis as discrete structures, independent of other pairs of chromosomes.
The sorting of chromosomes into pre-gametes from every homologous pair tends to be spontaneous.
Each parent synthesizes gametes which only contain half of their chromosome complement.
Although the size and morphology of the male and female gametes (sperm and egg) vary, they have the same number of chromosomes, indicating similar genetic contributions from each parent.
During fertilisation, the gametic chromosomes combine to produce offspring with the same number of chromosomes as their parents.
Despite compelling correlations between the behavior of chromosomes during meiosis and the abstract laws of Mendel, the Chromosomal Theory of Inheritance was proposed long before there was any direct evidence that traits on chromosomes were being carried. Critics have pointed out that people have characteristics that segregate far more individually than genes. It was only after several years of crossing with the fruit fly, Drosophila melanogaster, that Thomas Hunt Morgan gave experimental evidence to support the inheritance theory of Chromosomes.
Importance of Multiple Choice of Questions
This collection of Multiple - Choice Questions & Answers (MCQs) focuses on " Chromosomal Theory of Inheritance." These questions are short and sharp which means that in a test situation more of them can be asked to give a student a more thorough examination of how much they understand about a given topic.
Solved Multiple Choice Questions of Chromosomal Basis of Inheritance
1.The chromosomal inheritance theory has been proposed by____________.
a) Mendel
b) Watson and Crick
c) Darwin
d) Sutton and Boveri
Answer: d
Explanation: In the days of Mendel and Darwin the chromosomal inheritance hypothesis was unknown. Sutton and Boveri suggested this while Watson and Crick gave the DNA structure.
2. Which of the following does not fully agree with inheritance chromosomal theory?
a) The genes are located on the chromosome.
b) The genes on the same chromosome are always passed together.
c) The genes are located linearly on the chromosomes.
d) The distance between two genes can be mapped.
Answer: b
Explanation: Genes from the same chromosome can also exhibit independent assortment by recombination. Very close gene however tends to be linked and transmitted together.
3. When you cross a white - eyed female drosophila with a red-eyed male drosophila, what is your male and female offspring 's color of eyes?
a) Both red eyed.
b) Both white eyed.
c) Red eyed daughter and white eyed son.
d) Red eyed son and white eyed daughter.
Answer: c
Explanation: The eye colour of Drosophila is an X linked gene. So as the female is homozygous recessive white and the male has on red allele and one Y chromosome, sons will only get Y chromosomes from father. Sons will thus be white eyed while daughters will be red eyed.
4. The chromosomal inheritance theory clearly violates which of the following laws?
a) Law of dominance
b) Law of segregation
c) Law of independent assortment
Answer: c
Explanation: The chromosomal inheritance hypothesis violated none of Mendel 's laws, as the only distinction was the genes found in the chromosome, other than the laws being as they were.
Answerved:
5.The centromere is the portion of the chromosome in which___________.
(a) Nicking occurs
(b) Chromatids are attached
(c) Nucleoli are formed
(d) Crossing over takes place
Answer: (b) Chromatids are attached.
6.The chromosome ends are named as___________.
(a) Satellites
(b) Centromeres
(c) Telomeres
(d) Kinetochore
Answer: (c) Telomeres.
7.The first chromosomes were detected by___________.
(a) Fleming
(b) Waldeyer
(c) Strasburger
(d) Hoffmeister
Answer: (d) Hoffmeister.
8.A chromosome with a centromere subterminal is___________.
(a) Acrocentric
(b) Acentric
(c) Metacentric
(d) Telocentric
Answer: (a) Acrocentric.
9.The giant chromosome with various chromonemata is___________.
(a) Heterochromosome
(b) Polytene chromosome
(c) Lampbrush chromosome
(d) Supernumerary chromosome
Answer: (b) Polytene chromosome.
10.A chromosome with a centromere is called near the middle___________.
(a) Metacentric
(b) Acrocentric
(c) Telocentric
(d) Submetacentric
Answer: (d) Submetacentric.
11.Puffs or balbiani rings in the chromosome of the salivary gland are the locations of___________.
(a) Protein synthesis
(b) RNA synthesis
(c) DNA replication
(d) DNA duplication
Answer: (d) DNA duplication.
12.Chromosome inheritance theory was proposed by___________.
(a) Sutton in 1902.
(b) Boveri in 1902.
(c) Correns in 1909.
(d) Sutton and Boveri in 1902.
Answer: (d) Sutton and Boveri in 1902.
13.There are more than 200 chromosomes present in___________.
(a) Dog
(b) Amoeba
(c) Chicken
(d) Gorilla
Answer: (b) Amoeba.
14.A colour blind daughter can be born if the___________.
(a) Father is normal and the mother is a carrier.
(b) Father is normal and the mother is colour blind.
(c) Father is colour blind and mother is a carrier.
(d) Father is colour blind and mother is normal.
Answer: (c) Father is colour blind and mother is a carrier.
15.A somatic cell in a person is composed of___________.
(a) No gene on the sex chromosome.
(b) Genes on only on sex chromosomes.
(c) Two genes for every sex-linked character.
(d) Only one sex-linked gene for each character.
Answer: (d) Only one sex-linked gene for each character.
Test Your Knowledge:
1. X-linked dormant traits in humans (or in Drosophila) are observed ________.
in more males than females
in more females than males
in males and females equally
in different distributions depending on the trait
2.The first proposal that chromosomes may physically exchange segments came from the microscopic identification of ________.
synapsis
sister chromatids
chiasmata
alleles
3.What frequency of recombination corresponds to independent assortment and lack of linkage?
0
0.25
0.50
0.75
4.Which recombination frequency agrees to perfect linkage and disobeys the law of independent assortment?
0
0.25
0.50
0.75
FAQs on Chromosomal Theory of Inheritance: MCQs for Students
1. What are the key principles of the Chromosomal Theory of Inheritance that are important for solving MCQs?
The Chromosomal Theory of Inheritance states that genes, which are the units of heredity, are located on chromosomes. Key principles to remember for MCQs are:
- Chromosomes act as vehicles of heredity, carrying genes from one generation to the next.
- Both chromosomes and Mendelian factors (genes) exist in pairs in diploid organisms.
- The two alleles of a gene pair are located on homologous sites on homologous chromosomes.
- The segregation of chromosomes during meiosis is the physical basis for the segregation of alleles.
- The principle of independent assortment can be explained by the independent assortment of chromosomes during meiosis.
2. Who proposed the Chromosomal Theory of Inheritance and what were their key observations?
The Chromosomal Theory of Inheritance was independently proposed by Theodor Boveri and Walter Sutton in 1902. They observed a strong parallel between the behaviour of chromosomes during meiosis and the behaviour of Mendel's hereditary 'factors' (genes). Their key observation was that the pairing and separation of a pair of chromosomes during meiosis would lead to the segregation of a pair of factors they carried.
3. What experimental evidence, often tested in exams, supports the Chromosomal Theory of Inheritance?
The most significant experimental verification of the Chromosomal Theory of Inheritance came from the work of Thomas Hunt Morgan on the fruit fly, Drosophila melanogaster. He discovered that the gene for eye colour in fruit flies was located on the X-chromosome. He observed that the inheritance pattern of the white-eye trait was directly tied to the inheritance of the X-chromosome, providing the first concrete evidence that a specific gene resides on a specific chromosome.
4. Why was Drosophila melanogaster considered an ideal organism for verifying the Chromosomal Theory of Inheritance?
T.H. Morgan chose Drosophila melanogaster for his genetic studies due to several key advantages, which are common conceptual questions. These include:
- A very short life cycle (about two weeks), allowing for rapid generational studies.
- High reproductive capacity, as a single mating produces a large number of offspring.
- Clear and easy differentiation between male and female flies.
- Many types of hereditary variations that can be observed with low-power microscopes.
- They can be easily grown in a simple synthetic medium in the laboratory.
5. How does the concept of linkage and recombination provide further proof for the Chromosomal Theory?
The concepts of linkage and recombination strengthen the Chromosomal Theory. Linkage is the tendency of genes located on the same chromosome to be inherited together, which physically demonstrates that genes are indeed on chromosomes. Recombination, or crossing over, is the process where linked genes can be separated, creating new combinations of traits. This phenomenon not only proved that genes are arranged linearly on a chromosome but also allowed for the creation of genetic maps, further solidifying the chromosome as the physical basis of heredity.
6. What is the fundamental difference between chromosomal inheritance and cytoplasmic inheritance?
The primary difference lies in the location of the genetic material. Chromosomal inheritance involves genes located on the chromosomes within the cell's nucleus and follows Mendelian patterns of inheritance. In contrast, cytoplasmic (or extra-chromosomal) inheritance involves genes located in organelles within the cytoplasm, such as mitochondria and chloroplasts. This type of inheritance is typically non-Mendelian and is often passed down maternally, as the egg cell contributes the bulk of the cytoplasm to the zygote.
7. How did the Chromosomal Theory of Inheritance advance our understanding beyond Mendel's laws?
Mendel proposed the existence of 'factors' (genes) that control traits and described their patterns of inheritance, but he was unaware of their physical location or nature. The Chromosomal Theory of Inheritance provided the physical basis for Mendel's principles. It identified chromosomes as the cellular structures that carry these genes. This theory effectively united two fields of biology: cytology (the study of cells) and genetics (the study of heredity), by showing that the behaviour of chromosomes during cell division explained Mendel's abstract laws.
