Content Writer-SME | Updated On - Aug 5, 2024
The primary difference between chromosomes and genes arises on the basis of their structure and functions. The segment of DNA is called gene which is responsible for the transmission of traits. On the other hand, chromosomes are the hereditary structure made up of DNA and proteins. Both chromosomes and genes play significant roles in carrying the genetic information from one generation to other (parents to offsprings).
What are Chromosomes?
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Chromosomes are thread-like complex structures that is wrapped with DNA and proteins. They are responsible for carrying the genetic information from one generation to another. There are 46 chromosomes (23 pairs) present in the human body which are further categorized into autosomes and allosomes.
- Autosomes are the point of difference between male and female organisms
- Male organism contains XY chromosomes whereas presence of XX chromosomes is the indication of female organism.
- Each chromosome constitutes a genetic code from which a new organism is developed.
- The major role of chromosomes are seen during gene expression.
Functions of Chromosomes
The important roles of chromosomes in our body are as follows:
- They are responsible for storing the genetic information which are needed for the growth and development of an organism.
- Chromosomes are considered as hereditary units which help in the sex determination of a living organism.
- The presence of two X chromosomes is a genetic indication of a girl child, while one X and one Y chromosome indicates a male child.
- Chromosomes contribute to gene expression and determine the traits or characteristics of an individual.
- They also play a major role in translation and gene regulation.
What are Genes?
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Genes are defined as the hereditary units that are present in the chromosomes. They are responsible for protein coding.
- Each cell in the human body comprises about 3000 genes.
- They undergo mutations in the coded protein or RNA which results in changes in the traits of individuals.
- Genes are composed of nucleotide bases; adenine, guanine, cytosine, and thiamine.
Functions of Genes
As mentioned earlier, genes are a part of chromosomes that perform several functions such as:
- They are responsible for controlling the functions of DNA and RNA.
- Genetic tests are carried out to predict cancer, identify diseases in babies, and recognize mutations in genes.
- Genes control the synthesis of proteins.
Differences Between Chromosomes and Genes
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The differences between chomosomes and genes are discussed below in detail:
| Parameters | Chromosomes | Genes |
|---|---|---|
| Definition | Thread-like structure made up of DNA and proteins and carry genetic information. | Parts or segments of DNA that are found inside the chromosomes. |
| Visibility | Visible under the microscope. | Not visible under the microscope. |
| Occurrence | Occurs in pairs. | Occurs in pairs. |
| Composition | DNA and Proteins. | Either DNA or RNA. |
| Locus | One chromosome constitutes several genes. | Only one gene is the locus on a chromosome. |
| Mutation | Significantly Large | Small |
| Mutation Type | Chromosomal abnormalities. | Point mutations and frameshift mutations. |
Moreover, the relationship between chromosome and gene is best understood with the help of digram shown below:
Chromosomes and Genes
In conclusion, chromosomes and genes are two fundamental units of genetic inheritance. Chromosomal disorders and genetic diseases are explained with better understanding of chromosomes and genes. Mutation in genes affect a specific segment of DNA whereas in the case of chromosomal mutation, entire chromosomes are affected.
Things to Remember
- Chromosomes and genes differ in their functions inside the cell.
- Chromatin is a compacted structure of DNA and proteins that form a chromosome.
- The complete set of genetic information in an organism is the genome.
- The different forms of genes that occur at a particular location on a chromosome are called alleles.
- Genes are present in chromosomes at a specific position called the locus.
Previous Years Questions
- Which of the following is an example of pleiotropy ?…..[ CUCET 2011]
- Who proposed the chromosomal theory of inheritance ?….[CUCET 2010]
- The children of a father with type 'O' blood and mother with type….[COMEDK UGET 2012]
- Epicanthus skin fold above the eyes and transverse palmer….[COMEDK UGET 2007]
- Distance between the genes and percentage of….[COMEDK UGET 2015]
- Which one of the following is a sex-linked disease….[CUCET 2010]
- The science that deals with the application of principles….[CUCET 2010]
- A 10 years old patient is found to have the following….[COMEDK UGET 2012]
- Which of the following genes shows the heterozygous...[BHU UET 2008]
- Which chromosomal constitution refers to Jacob's syndrome….[BHU UET 2012]
- Which of the following is an example of intergenic gene….
- Which of the following is not considered as a mutagen…
- Haemophilia is an example of….
- In order to lessen the suffering of phenylketonurics...[AMUEEE 2014]
- In Mendel's experiments with garden pea, round seed shape..[JKCET 2015]
- Genotypic and phenotypic ratio in monohybrid cross remains..[JKCET 2011]
Sample Questions
Ques. Do abnormalities take place in chromosomes? If yes, what are they? (3 marks)
Ans. Yes, chromosomal abnormalities take place and they are further categorized into two twpes: structural abnormalities or abnormalities in the number of chromosomes.
- When chromosomes fail to separate at the time of cell division abnormalities in the chromosomal number occur.
- One example is Down Syndrome which gives rise to 47 chromosomes instead of 46.
- Structural abnormalities include deletion, amplification, or translocation of chromosomes.
Ques. Mention the categories of human chromosomes. (3 marks)
Ans. There are two types of human chromosomes namely: sex chromosomes and autosomes.
- There are 23 pairs of chromosomes in humans out of which 22 pairs are autosomes while and one left is the sex chromosome.
- Sex chromosomes are those that determine the sex of the child.
- A male has a single X chromosome and a Y chromosome (XY), while two X chromosomes (XX) are found in females.
Ques. Mention any 3 chromosomal disorders. (2 marks)
Ans. Abnormalities in the structure or number of chromosomes are directly linked to chromosomal disorders. Some major chromosomal abnormalities that are rarely seen are mentioned below:
- Kleinfelter’s Syndrome
- Down Syndrome
- Edward Syndrome
Ques. How are chromosomes and genes interrelated? (2 marks)
Ans. Chromosomes and genes are the hereditary units that are responsible for determining characteristics or traits in an organism.
- Genes are DNA segments, while chromosomes are long strings composed of many genes.
- It is known that each cell contains 46 chromosomes and each chromosome have around 1000-3000 genes present.
Ques. Differentiate between gene and allele. (3 marks)
Ans. The table below shows the difference between the two:
| Gene | Allele |
|---|---|
| It is a sequence of DNA. | The variant form of a gene is an allele. |
| A gene has two alleles. | Alleles are either dominant or recessive. |
| Genes are responsible for the expression of traits. | Alleles play a major role in the expression of variation of a specific trait. |
| Different alleles are found in genes. | A pair of alleles for a particular gene is found in individuals. |
Ques. What types of traits are determined by genes? (2 marks)
Ans. The following traits are determined by genes:
- Eye colour
- Height
- Skin colour
- Hairline
- Hair colour
- Blood group
- Risk of diseases like breast cancer, sickle cell anemia
Ques. Who discovered chromosomes? Also, name the scientist who coined the term ‘genes’. (2 marks)
Ans. Chromosomes were discovered by Walther Flemming in 1882. Wilhelm Johannsen was the scientist who coined the term gene.
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