Matric Notes Biology Class 10th Ch 15 Inheritance Long Questions
To view other notes of Biology 10th. Click Here.
Q1: Relate the structure of chromosome with DNA and gene. Draw a concept chart to explain your answer. Ans: They are related as:
➢ Chromosomes:- A chromosome is a deoxyribonucleic acid molecule with part or all of the genetic material of an organism.
Structure of chromosomes: Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
Centromere: Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.”
The short arm: The short arm of the chromosome is labeled the “p arm.”
The long arm: The long arm of the chromosome is labeled the “q arm.”
Location of centromere: The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specific genes
➢ DNA: DNA (or deoxyribonucleic acid) is the molecule that carries the genetic information in all cellular forms of life and some viruses. It belongs to a class of molecules called the nucleic acids, which are polynucleotides - that is, long chains of nucleotides.
Nucleotide: Each nucleotide consists of three components:
• a five-carbon sugar molecule (deoxyribose in the case of DNA)
• The backbone of the polynucleotide is a chain of sugar and phosphate molecules. Each of the sugar groups in this sugar-phosphate backbone is linked to one of the four nitrogenous bases.
Strand of polynucleotides:
➢ Genes: The gene is the basic physical and functional unit of heredity. It consists of a specific sequence of nucleotides at a given position on a given chromosome that codes for a specific protein (or, in some cases, an RNA molecule).
Gene nucleotide: Genes consist of three types of nucleotide sequence:
• non-coding regions, called introns, which do not specify amino acids
• regulatory sequences, which play a role in determining when and where the protein is made (and how much is made)
Number of genes: A human being has 20,000 to 25,000 genes located on 46 chromosomes (23 pairs). These genes are known, collectively, as the human genome.
Q2: Explain with the help of diagram the relationship amongst DNA, RNA and proteins.
Ans: They are related as:
➢ DNA: DNA is the basic hereditary material in all cells and contains all the information necessary to make proteins. DNA is a linear polymer that is made up of nucleotide units.
Nucleotide: The nucleotide unit consists of a base, a deoxyribose sugar, and a phosphate. There are four types of bases: adenine (A), thymine (T), guanine (G), and cytosine (C).
Complementary bases: In normal DNA, the bases form pairs: A to T and G to C. This is called complementary. A duplex of DNA is formed by two complementary chains that are arranged in an anti-parallel manner.
➢ RNA:- RNA is a polymer that contains ribose rather than deoxyribose sugars. The normal base composition is made up of guanine, adenine, cytosine, and uracil.
Function of RNA: When a cell receives a signal saying that a certain protein is needed, the code for producing protein is made. The DNA double helix unwinds and one strand of the helix becomes a template for producing the protein coding template. This template is a single strand of opposite bases (from DNA) and is called RNA (Ribonucleic Acid).
OR
The form of RNA in which genetic information transcribed from DNA as a sequence of bases is transferred to ribosomes.
Transcription: mRNA it serves as a code messenger between DNA and protein. The process of creating a mRNA from DNA is called transcription.
➢ Proteins: Any of a class of nitrogenous organic compounds which have large molecules composed of one or more long chains of amino acids.
Large molecules composed of one or more chains of amino acids in a specific order determined by the base sequence of nucleotides in the DNA coding for the protein.
Function of protein:
❖ They are the essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, etc., and as enzymes and antibodies.
Diagram:
Q3: Explain why Mendel selected peas as a subject for studying genetics?
Ans: Gregor Mendel chose the pea plants for his experiments because the garden pea is an ideal subject in the study of genetics for the following reasons:
Annual plant: Garden pea plant is an annual plant. Its short life cycle make it possible to study several generations within a short period
Bisexual plant: It has perfect bisexual flowers containing both male and female parts. The flowers are predominantly self-pollinating.
Self-fertilization: Because of self-fertilization plants remain genetically pure. It is, therefore, easy to get pure lines of several generations.
Cross pollination: Experimental cross pollination can be done easily in pea plant.
Quick and easy to grow: He chooses them because they are quick and easy to grow and several peas are produced in each pod. It is fortunate that he chooses the plant that he did, and that he chooses the characteristics he did to observe. Some plants would have been much more difficult to work with.
Seven traits: Because pea plants are easy to propagate and have 7 observable traits like Seed Shape, seed color, Seed coat, color, pod shape, flower position and stem length.
Reproduce quickly: Pea plants were probably picked because of their ability to reproduce quickly. If Gregor Mendel had used an animal, he would have had to wait many years before being able to study the passing on of traits.
Larger corolla: Pea plants (Leguminosae) have an irregular flower in which the top part of the corolla is much larger than the lower part.
No freely pollination: A pea flower, it looks much like a snap dragon bloom. This feature keeps the flowers from freely pollinating each other by wind, as they are tightly shut. If protected from pollinating insects, they will only self-pollinate, or if the anthers are clipped off they can be very selectively pollinated by a person. This gave Mendel much tighter control over the crossbreeding of the plants.
Q4: Explain the law of independent assortment with the help of an example and chart.
Ans: Mendel law of independent assortment:- Mendel law of independent assortment states “When two traits are together, followed in the same cross, the distribution of the allele for the one trait in the gametes does not affect the distribution of the allele for the other trait.”
Explanation:
2. He made a series of crosses involving two traits, or dihybrid crosses.
3. These crosses are between plants that differed from one another in two distinct traits.
4. Mendel crossed true breeding plants having round yellow seeds (RRYY) with plants having wrinkled green seeds (rryy).
5. The seeds of F1 generation offspring showed only the dominant characteristics in seeds, which are seeds of a round and yellow phenotype.
6. When F1 hybrids were self-fertilized, four different types of seeds were found among the F2 generation.
7. The ratio of these types was 9/16.
8. The later type’s yellow, wrinkled and green round was not seen in either.
9. The F2 generation appeared in the ratio of 9:3:3:1.
Q5: Describe the sources of variations. Explain the importance of variations in organisms.
Ans: Variations:
• Variation is necessary for species to become adapted to their environment.
• Variation also enables the species to change with the environmental changes.
Sources of variation:
Variation has the following three main causes/sources.
2. Mutation
3. Environment
1. Genetic recombination:- If we study the process of sexual reproduction carefully then we will see that three random components of sexual reproduction are responsible for bringing genetic diversity. These are as follows.
a. Independent assortment of chromosomes: In sexual reproduction, the process of meiosis is required for the formation of gametes. The reduction in the number of chromosomes is achieved by separating the members of each pair of homologous chromosomes into different nuclei. Independent assortment of homologous takes place, which is responsible for the formation of new chromosomes combination in the daughter cells.
b. Crossing over: Sexual reproduction promotes variation because each gamete (sperm or egg) contains a mixture of genes from two different parents. Crossing over promotes variation. During prophase I of meiosis, crossing over results in chromosomes that have some genes from one parent and some genes from the other parent. The phenomenon of crossing over further promote genetic variability produced by independent assortment of chromosomes. If no crossing over occurs meiosis could produces two genetic types of gametes. With crossing over more than two types of gamete can result.
c. Random fertilization: Each gamete has a unique genetic composition, because of the shuffling of genes and chromosomes in meiosis. When gametes combine randomly during fertilization, the organism produced is different from all others of the species.
2. Mutation:
Mutation is a spontaneous change in a gene, which alter gene product. It is defined as any change in the nucleotide sequence of DNA. Alleles arise by mutation. The original allele is termed as wild type of mutant allele. If there were no mutation, there would be no biological evolution.
3. Environment:
Although environment has no role in the initial production of varieties, they are randomly produced. Once the variants produced, they are then acted upon in the environment by the process of natural selection. The variants, which are best suited in a particular environment, have more chance to survive or being selected by nature. Accumulation of such traits generation after such trait generation results ultimately in the production of new species.
➢ Importance of variation: Variation causes evolution.
Evolution: Evolution is the slow and gradual change in organisms with passage of time. Variations prerequisite evolution: -
2. If all individuals in a species had the exact same set of genes, their offspring would all be the same, and would all have an equal chance of survival.
3. It’s the variations in genes, which are expressed as variations in traits that cause some individuals to thrive and others to fall prey to predators and other threats in their environment.
Examples with explanation: -
2. Finches have different kinds of beaks, each one best suited for a particular task.
3. Some beaks are best for cracking hard nuts, others for reaching into light spaces, still others for eating small seed.
4. The type of beak that an individual finch has, will affect that finch’s ability to survive in a given environment.
5. If there is drought that kills the plants that produce small seeds, the finches with large, strong beaks that can crack hard nuts will do better than the finches whose beaks were best suited to eating the now scare small seeds.
6. Natural selection act on observable traits such as the size, strength and shape of the finch’s beaks.
Q6: Draw a cross between two pea plants. One of them has round green seeds (RRyy) while the other has wrinkled yellow seeds (rrYY).
Ans:
Post a Comment