What is the Chromosomal Basis 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
