Genetics and Evolution MCQ Quiz - Objective Question with Answer for Genetics and Evolution - Download Free PDF

The correct answer is 1/4

Explanation:

• A pedigree chart is a diagram that shows the occurrence and appearance of phenotypes of a particular gene or organism and its ancestors, often used to determine inheritance patterns.
• Carriers are individuals who have one recessive allele (disease mutation) and one normal allele. They do not show symptoms of the disease but can pass the mutation to their offspring.

X-linked Recessive Mutation:

• Typically, X-linked recessive traits are more common in males because they only have one X chromosome.
• Affected males pass the trait to all their daughters, who are carriers, and to none of their sons.
• Carrier females (having one normal and one affected X chromosome) can pass the trait to both sons and daughters.

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Thus, the correct answer is 1/4 (XX^c)

The correct answer is Analogy, convergent

Concept:

• Evolution refers to the process through which organisms change over time as a result of changes in heritable physical or behavioral traits.
• Two key evolutionary concepts involved in comparing structures in organisms are homology and analogy.
• Homologous structures are defined as the organs of different animals having similar structures but differ in their functions. Homology indicates common ancestry. Homology is based on divergent evolution Examples
  • Forelimbs of man, cheetah, whale, and bat
  • Thorns and Tendrils of Bougainvillea and Cucurbita
  • Vertebrate heart or brain
• Analogous structures are defined as the organs of different animals having different structures but performing the same functions. Analogy is based on convergent evolution. Examples:
  • Wings of insects and birds. 
  • Sweet potatoes (root modification) and potatoes (stem modification)
  • Eye of octopus and of mammals
  • Flippers of Penguins and Dolphins

Explanation:

• Sweet potato and potato are examples of analogous structures. Despite having a similar function (storage of food), they arose from different origins. The sweet potato is a modified root, whereas the potato is a modified stem.

The correct answer is Phenotypic ratio - 9 : 3 : 3 : 1

Concept:

Mendel proposed some laws to explain his understanding of inheritance. Today, these are called the Principles or Laws of Inheritance.

1. ​Law of Dominance -  It is used to explain the expression of only the dominant character in a monohybrid cross in the F1 generation and the expression of both dominant and recessive in the F2 generation.
2. Law of segregation -  ​It states that the alleles do not show any blending. During gamete formation, the alleles segregate and pass equally and both the characters are recovered as such in the F2 generation.
3. Law of Independent Assortment - It states that during gamete formation, one pair of traits segregates from another pair of traits independently.

Explanation:

In pea plants:

• The round seed (R) is dominant over the wrinkled seed (r)
• The yellow color (Y) seed is dominant over the green color seed (y)

The cross is in the following,

F1:                                                  RrYy (Round and yellow)

Selfing of F1:     RrYy (Round and yellow)   X   RrYy (Round and yellow)

Gametes:                          RY, Ry, rY, ry      X     RY, Ry, rY, ry

The phenotypic ratio produced is 9: 3: 3: 1.

• 9 - Round yellow
• 3 - Round green
• 3 - Wrinkled yellow
• 1 - Wrinkled green

Therefore, in F2 generation two new combination of seeds Round yellow and wrinkled green seeds would be produced that differ from the parent type.

The correct answer is Non-Mendelian inheritance pattern

Explanation:

• Polygenic traits are traits controlled by multiple genes, often located on different chromosomes. These genes collectively contribute to the phenotype, and their effects are additive.
• Unlike single-gene traits studied by Mendel, polygenic traits do not follow simple dominant-recessive inheritance. Instead, they exhibit a Non-Mendelian inheritance pattern.
• Examples of polygenic traits include skin color, height, eye color, and weight in humans. These traits show a continuous range of variation rather than discrete categories.
• Environmental factors also play a significant role in the expression of polygenic traits.
• Polygenic traits are inherited in a manner that does not conform to Mendel’s laws of inheritance. The phenotypes result from the interaction of multiple genes, each with a small, cumulative effect.

Other Options:

• Mendelian inheritance pattern: This applies to single-gene traits where one gene determines the phenotype, with clear dominant and recessive alleles. Polygenic traits do not follow this pattern, as they are influenced by multiple genes and exhibit a range of phenotypes.
• Autosomal dominant pattern: In this inheritance pattern, a single copy of a dominant allele on an autosome is sufficient to express the trait. 
• X-linked recessive inheritance pattern: This pattern refers to traits caused by recessive alleles on the X chromosome. These traits are often seen more in males due to their single X chromosome. 

The correct answer is Statements 1 and 3 are correct.

Acc. to NCERT:

• Giant ferns (pteridophytes) were present but they all fell to form coal deposits slowly.
• Some of these land reptiles went back into water to evolve into fish like reptiles probably 200 mya (e.g. Ichthyosaurs).
• The land reptiles were, of course, the dinosaurs. The biggest of them, i.e., Tyrannosaurus rex was about 20 feet in height and had huge fearsome dagger like teeth.
• About 65 mya, the dinosaurs suddenly disappeared from the earth. We do not know the true reason. Some say climatic changes killed them.

Explanation:

• Statement 2: Certain land reptiles transitioned back to water and evolved into fish-like reptiles such as Ichthyosaurs around 100 million years ago is Incorrect because Land reptiles evolve back into water around 200 mya.

Concept-

• Gregor Mendel conducted hybridization experiments on garden peas for seven years (1856-1863).
• A dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits.
• A hybrid organism is one that is heterozygous, which means that carries two different alleles at a particular genetic position.
• Therefore, a dihybrid organism is one that is heterozygous at two different genetic loci.
• Gregor Mendel performed dihybrid crosses on pea plants and discovered a fundamental law of genetics called the Law of Independent Assortment.

Explanation-

• Mendel selected traits for dihybrid cross for his experiments-
  • Colour of cotyledons- Yellow (Y) and Green (y).
  • Seed shape - Round (R) and Wrinkled (r).

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• The phenotypic ratio produced is 9: 3: 3: 1.
• The genotypic ratio produced is 1: 2: 2: 4: 1: 2: 1: 2: 1.

Therefore the 9 types of genotype and 4 types of the phenotype are present in the mendelian dihybrid cross.

Additional Information

• Monohybrid Cross
  • Phenotypic ratio- 3: 1
  • Genotypic ratio- 1: 2: 1

The correct answer is a Dihybrid cross.

• Mendel's law of independent assortment can be demonstrated by the Dihybrid cross.

Key Points

• Mendel's law of independent assortment:
  • Independent assortment is a fundamental principle of genetics evolved by Gregor Mendel in the 1860s.
  • Mendel formulated this principle after discovering another principle known as Mendel's law of segregation, both of which govern heredity.
  • The law of independent assortment asserts that an assortment of each pair of traits is independent of the other, i.e.during gamete formation, one pair of traits segregates from another pair of traits independently. 
  • Dihybrid cross – Cross is made between a homozygous dominant parent to another homozygous recessive parent on the basis of twocharacters.
  • By using this cross, Mendel postulated the Law of Independent Assortment.

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Explanation:

• Mendel selected traits for dihybrid cross for his experiments-
  • Colour of cotyledons- Yellow (Y) and Green (y).
  • Seed shape - Round (R) and Wrinkled (r).
• The phenotypic ratio produced is 9: 3: 3: 1.
• The genotypic ratio produced is 1: 2: 2: 4: 1: 2: 1: 2: 1.
• This proved that two pairs of alleles assorted independent of each other.

Therefore, Mendel's law of independent assortment can be demonstrated by a dihybrid cross.

Additional Information 

• Monohybrid cross – Cross is made between a homozygous dominant parent to another homozygous recessive parent on the basis of one character.
  • By using this cross Mendel postulated the Law of dominance and the Law of Segregation.

Concept:

• The founder effect occurs when a small population gets drifted from the parent population and becomes a new population.
• Allele frequency changes as compared to their parent population and thus forming a new population with a new genotype.

Explanation:

• Option 1: Genetic drift is the change in allele frequencies that occurs by chance. It occurs in a small population. The founder effect is a result of genetic drift.
• Option 2: Natural selection is a process by which the organism more fitted to the environment will survive and reproduce to form more of its kind. They are more adapted to their environment.
• Option 3: Genetic recombination is the process of the exchange of DNA fragments between two different chromosomes leading to variation.
• Option 4: Mutation is the change in DNA sequence due to errors in DNA replication, any exposure to mutagens, etc.

So, the correct answer is option 1.

The correct answer is  All of these.

Explanation-

Gregor Mendel is regarded as the "father of modern genetics" due to his groundbreaking experiments on pea plants in the mid-19th century. His studies led him to formulate the fundamental principles of heredity.

Mendel conducted his experiments with seven pairs of contrasting characters in pea plants. These are traits that exist in one of two forms. The seven characters that Mendel focused on were:

• Seed Shape: This can be either round (dominant) or wrinkled (recessive).
• Seed Color: This can be yellow (dominant) or green (recessive).
• Flower Color: This can be violet (dominant) or white (recessive).
• Flower Position: The flowers on the plant can be axial (dominant), meaning they are located along the stem, or terminal (recessive), meaning they are located at the end of the stalk.
• Pod Shape: The pod can be inflated (dominant) or constricted (recessive).
• Pod Color: The pod can be green (dominant) or yellow (recessive).
• Stem Length: The stem can be long (dominant) or short (recessive).

For his experiment, Mendel cross-fertilized plants that had different traits for the same character (e.g., a plant with round seeds and a plant with wrinkled seeds) and observed the offspring in the subsequent generations. He performed these experiments over many years and on thousands of pea plants.

The correct answer is Autosomal recessive inheritance.

Concept:

• In Autosomal recessive inheritance, the term 'recessive' refers to the fact that two copies of the gene are required to have the trait and disorder in the case of a mutated gene.
• One gene is inherited from the father and one from the mother out of the two copies.
• If a person carries one defective recessive gene and one normal recessive gene, he or she will be a carrier but will not develop the disease.

Explanation:

• Sickle cell anaemia is a group of disorders that affect the molecule haemoglobin (found in red blood cells) that transports oxygen to cells throughout the human body.
• This disorder is distinguished by a low number of red blood cells (anaemia), periodic episodes of pain and repeated infections.
• Sickle cell anaemia is an autosomal recessive disease. 
• A mutation in the haemoglobin-β gene on chromosome 11 causes sickle cell disease. As a result, the haemoglobin (Hb) is defective.
• These defective haemoglobin molecules cluster together after losing oxygen, resulting in the formation of rod-like structures.
• The red blood cells stiffen and form a sickle shape.

The correct answer is option 4.

Concept:

• Sex determination is the mechanism that determines the biological sex of an individual.
• Henking (1891) observed a nuclear structure and named it X-body later named X- chromosomes.
• He also observed that after spermatogenesis, half of the sperms receive this X-body, and half of them did not.
• As the X-chromosome is involved in the sex determination process, it is termed a sex chromosome.
• The other chromosomes that are not involved in sex determination are known as autosomes.

Explanation:

Option 1: 

• XX/XY type - The females possess a pair of X-chromosomes, while the males possess one X-chromosome and one Y-chromosome. Example. - Man, Monkey.
• Platypus belongs to the class of mammals.
• Therefore, this is not the correct answer.

Option 2: 

• XY/XO type - Snails belong to mollusks.
• In this type male individuals produce two different types of gametes.
• Thus, the sperm determines the sex of the offspring. It involves two kinds of sex-determining mechanisms - XO type and XY type.
• Therefore, this is not the correct answer.

Option 3: 

• XX/XO type - Cockroach belongs to insects.
• XX/XO is observed in a sizable amount of insects e.g., Grasshopper.
• The number of chromosomes is different in male and female individuals.

Option 4: 

• ZW/ZZ type: In this type, the females produce 2 different types of gametes while the males produce a single type of gamete. Females have one Z and one W chromosome, whereas males have a pair of Z chromosomes besides the autosomes.  Example: Birds.
• Therefore, peacocks will have ZW/ZZ type.
• So, the correct answer is option 4.

Additional Information

• Male heterogamety: In XO type and XY type, males produce two different types of gametes, (a) either with or without X-chromosome or (b) some gametes with X-chromosome and some with Y-chromosome. Such types of sex determination mechanisms are designated to be an example of male heterogamety.
• Female heterogamety: In these organisms, the females have one Z and one W chromosome, whereas males have a pair of Z-chromosomes besides the autosomes. Two different types of gametes in terms of the sex chromosomes are produced by females, i.e., female heterogamety.

The correct answer is 'G.J. Mendel'.

 Key Points

• Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance.
• He deduced that genes come in pairs and are inherited as distinct units, one from each parent.
• Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits.
• Mendel's law of inheritance is as follows:
• Law of segregation: During gamete formation, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.
• Law of independent assortment: Genes for different traits can segregate independently during the formation of gametes.

Hint

• It is based on Hardy-Weinberg equation: p² + q² + 2pq = 1​

Key Points

• G.H. Hardy and Wilhelm Weinberg independently described the basic principle of population genetics that is known as the Hardy-Weinberg principle.
• It states that allele frequencies in a population remains constant from generation to generation.
• The gene pool remains constant and is referred to as genetic equilibrium or Hardy-Weinberg equilibrium.
• Gene pool - It is the total of all genes and alleles in a population.
• This is supported by a mathematical equation that can be used to calculate genotype frequencies in a population at equilibrium.

Important Points

Concept:

• Phenylketonuria is an autosomal recessive disorder, meaning the disease is expressed only in homozygous recessive condition.
• If we assume the dominant and recessive alleles as A and a, the genotypic conditions will be:
  • AA - Homozygous dominant
  • aa - Homozygous recessive
  • Aa - Heterozygous
• According to Hardy-Weinberg equation,

Sum of all allelic frequencies = 1

Therefore, p² + q² + 2pq = 1

or, (p + q)² = 1

where, p and q represent the frequencies of the alleles A and a respectively.

• Thus, the specific genotype frequencies are represented as:
  • p² - AA
  • q² - aa
  • 2pq - Aa

Calculation:

• It is given that the frequency of affected newborns is 1 in 14000.

Therefore, q² = 1/14000 = 0.0000714

or, q = 0.0084

Now, (p + q)2 = 1

or, p = 1 - q = 1 - 0.0084 = 0.9916

Therefore, 2pq = 0.0166 ≈ 0.017

• Thus, the frequency of heterozygotes will be 0.017.

Key Points

• Adaptive radiation is a process of evolution of different species in a given geographical area. 
• It starts from an ancestral stock and radiating or moving to other habitats. 
• It was first shown by Darwin while he studied the species of finches in the Galapagos islands.
• There were several species of finches that had diverged from the original seed-eating species.
• Competing with the same resources on the island allowed them to adopt with new beak features that reduced competition for survival.
• The feeding habit of Darwin's finches ranged from seeds to insects and many more.
• Similar example can be given for Australian marsupials and Australian placental mammals, that evolved within the continental island from an ancestral stock.
• The Australian placental mammals also show similarities with a corresponding marsupial. E.g.-Anteater and Numbat.

Additional Information

• Moths in England exemplify natural selection.
• A change was observed in the population of peppermoths of England after industrialization.
• Before industrialization, white-winged moths were more prevalent on the trees that were covered with whitish lichen, which grew in the absence of pollution.
• Post-industrialization, the trees became covered with soot and smoke, exposing the white-winged moths to predators.
• Here, the dark-winged or melanized moths survived better and hence became prevalent.
• In rural areas, however, the white-winged moths prevailed.
• This shows a directional selection in favour of the dark-winged moths in industrial are.