Hello students, on this page you will read in detail the important chapter of biology about chromosomes.
Let us read about Chromosomal and heredity in detail today.
what are chromosomes called
Chromosome was named by W. Waldair. cell During division, the chromatin breaks down or splits into smaller parts that form chromosomes.
Those individual protoplasmic units carrying genes which regularly multiply through successive cell divisions and maintain their individuality, morphology and function are called chromosomes.
The colorless material in which chromosomes are wrapped is called matrices. Whereas the material that transmits the genetic traits present in a chromosome is called a genome, the number of chromosomes is different in each species of organisms.
general structure of chromosome
The properties of all living beings are almost the same.
Generally the following structures are found in a chromosome.
The outermost thin membrane of the chromosome is called pellicle, it surrounds the homologous base material.
It is found inside the pellicle, in which chromonemata are located.
3. Chromatids or Chromonema
In each chromosome, chromatids or chromonema are found.
Button or knot-like structures are found at equal distances above the chromonemata, which are called chromomeres. Genetic units (genes) are located in the chromomere itself.
Each chromosome becomes synapsed by sinking or suppressing at one place, this narrow spot is called centromere or primary constriction. More than one constriction is found in any chromosome, it is called secondary constriction.
The front part of the secondary constriction of the chromosome is called the satellite.
sex determination in humans
The total number of chromosomes in humans is 46, which are found in the form of 23 pairs, in males (22 + xy) and in females (22 + xx).
In humans, 22 pairs are the same in male and female, but the 23rd pair is different, which is the main 23 (xy) pair of male in the determination of male and female genitalia.
definition of genetics
Those traits which are transmitted from generation to generation are called genetic traits The study of the methods and causes of transmission of genetic traits from generation to generation is called genetics.
The first information about heredity was given by Gregor Johann Mendel, a resident of Austria. That is why he is called the father of heredity. The pea plant was selected by Mendel for his genetics experiment.
Mender first studied the inheritance of one pair and then two pairs of opposite traits, which are called monohybrid and double-crossed crosses respectively.
Mander made a cross between tall (TT) and dwarf (tt) plants for a hybrid cross, then the phenotype ratio of the plant of F2 generation was 3 : 1 and genotype ratio 1 : 2 : 1.
Meander crossed the plants produced from round and yellow seeds (RRYY) and green and wrinkled seeds (rryy) for bi-directional cross, in which round and yellow seeds are effective.
Hence, the phenotype ratio of the plants of F2 generation is 9 : 3 : 3 : 1 and the genotype ratio of plants of the f2 generation is 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1.
On the basis of both types of experiments, Mender has given some rules of heredity, which are known as Mender’s law of heredity, out of these rules, the first and second rules are based on a cross cross and the third law is based on the double cross.
Menander has three laws.
law of effectiveness
When a pair crosses between a pure father or mother with reversing traits, dominant traits are revealed in the first generation while recessive traits are hidden.
Only dominant qualities are visible in the first generation, but recessive qualities are definitely present, this quality appears in the second generation.
law of separation
Both the factors of pairs of trait factors (genes) get separated while forming a pair and only one of these factors reaches any one gamete, this law is also called the law of purity of gametes.
law of independent matrices
When two pairs of opposite traits are crossed between plants, the separation of the two traits occurs independently. The heredity of one trait does not affect the other.
genetic diseases in humans
Humans have the following genetic diseases
1. Turner’s Syndrome
This disease mainly occurs in women, the number of chromosomes in a woman suffering from this disease is not 46, but it becomes less than 45. Due to which other symptoms arise in the body.
- Average height is much less than 5 feet 2 inches.
- The genitals are rudimentary.
- Their voice becomes heavy.
2. Klinefelter’s Syndrome
This disease mainly occurs in men, the number of chromosomes increases in men suffering from this, chromosomes become 47 instead of 46. In this, the testes of men are underdeveloped and breasts are developed like that of women, due to this the following physical deformities arise.
- The average height is not much less than 5 feet 6 inches.
- The voice does not become heavy but becomes thin.
- The genitals are underdeveloped or rudimentary.
- The mammary glands enlarge.
- Men suffering from this disease are impotent.
In this, the patient does not have the ability to recognize red and green colors, mainly males are affected by this disease, in females it occurs only when both its chromosomes (XX) are affected. The carriers of this disease are women.
In this disease, blood does not clot for half an hour to 24 hours (normal time interval is 2 to 5 minutes on average) after injury to the person.
It mainly occurs in men, in women, this disease occurs only when both its chromosomes (XX) are affected. The carriers of this Roh are women. Heldon believes that this disease started with Queen Victoria of Britain.
5. Down’s Syndrome
Patients suffering from this disease have slow intellect, crooked eyes, thick tongue and irregular body structure. It is also called Mangolism.
6. Patau’s Syndrome
In this, the upper lip of the patient is cut from the middle, there is a crack in the palate. In this disease, the patient can be affected by slow intellect, eye diseases etc.
number of chromosomes in animals
|pteridocites||1300 – 1600|
Genetics and chromosomes questions and answers
Question 1. By whom was the chromosome named?
Answer:- W Waldair
Question 2. How many chromosomes are there in humans?
Question 3. Who first gave information about heredity?
Answer:- Gregor Johann Mendel
Question 4. In which year did Gregor Johann Mendel give information about heredity?
Answer:- 1822 to 1884
Question 5. Who is called the father of heredity?
Answer:- Gregor Johann Mendel
Question 6. What are the traits that are transmitted from generation to generation?
Answer: Genetic Traits
Question 7. Who named the chromosomes?
Answer:- W. Voltaire
Question 8. W. In which year did Voltaire name the chromosomes?
Answer:- 1888 AD.
Question 9. What is the genetic material found in chromosomes called?
Question 10. How many essential amino acids are found in humans?
Question 11. s. In which year the modern ideology of gene was given by Benger?
Q12. s. Where does the unit of recombination of a gene’s function go to?
Question 13. How many types of sperm are produced by meiosis in spermatogenesis?
Answer:- 2 types
Question14. Where does fertilization take place in the case of a test tube baby?
Answer:- Inside the test tube
Question15. What is the number of chromosomes in mosquito?
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