Heredity -2 - Class 10 MCQ

Weight of body depends on diet and habits. If somebody is not eating he will definitely lose weight as the body fat will be used for production of energy once glycogen reserve finishes.

Continuous variation can be defined as the variations in the phenotypic traits in which a series of types are distributed on a continuum rather than separate groups. For example body weight.

New species may be formed if DNA undergoes significant change in germ cells. Changes in DNA will be inherited by the germ cells. Germ cells which when passes to the next generation will be inherited in the subsequent generations.

Change in the chromosome number makes a change in the gametes which leads to change in the gene pool and causes variation. 

Different eye colour is a genetic variation.

The earlobe variants found in human population are free and attached.
EXPLANATION:-
All the human beings have two types of earlobes.
One of such earlobes are the attached earlobes which are attached to the skin of human being near his or her ear . 2nd earlobes are the earlobes which are not so attached rather they are hanged freely

Both are modifications of root while potato is a stem modification and brinjal is a fruit.

1. Wing of a bird and wing of a bat are analogous.

Analogous structures are those that have evolved independently to serve a similar function but do not share a common ancestor. The wings of birds and bats are similar in function (both are used for flying), but they have evolved independently in these different groups of animals.

Both thorn of Bougainvillea and potato are modification of stem.

There are certain fossils of ancient reptiles which have both reptilian as well as feature of birds which proves that birds have evolved from reptiles.

Sexual reproduction leads to greater diversity in offspring by inheriting variations from parents, enhancing the chances of survival in changing environments and promoting evolutionary processes.

• The prevalence of traits in a population can suggest their age. Traits present in a larger portion of the population, like trait B at 60%, are often older, as they had more time to spread.


• However, without additional information on selective pressures, mutation rates, or environmental changes, determining which trait arose first is speculative.


• Thus, the correct answer is C: It cannot be determined solely based on prevalence.

 

• The Assertion is false because variations in a species primarily arise due to sexual reproduction, not asexual reproduction.
• The Reason is true as sexual reproduction indeed leads to greater diversity.
• However, the Reason is not the correct explanation of the Assertion since the Assertion itself is incorrect.

• (i): Asexual reproduction generates very minor differences due to small inaccuracies in DNA copying. This is accurate as asexual reproduction results in offspring that are almost identical to the parent, with only minor differences due to DNA copying errors.
• (ii): Sexual reproduction maximizes the number of successful variations. This is true because sexual reproduction involves the combination of genetic material from two parents, leading to greater genetic diversity.
• (iv): Inheritance from previous generations provides a common basic body design and subtle changes for the next generation. This statement is correct as it indicates how inherited traits provide a fundamental structure while allowing for variations.
• (iii): All variations in a species have equal chances of surviving in the environment. This statement is incorrect. Different variations have different survival advantages depending on the environment, which is the basis for natural selection.

Therefore, the correct answer is Option C: (i), (ii) and (iv).

Gregor Mendel conducted experiments primarily focused on plant biology, particularly using garden peas. His work with pea plants allowed him to establish the fundamental principles of heredity, leading to the foundation of modern genetics.

Mendel proposed that two copies of factors controlling traits are present in sexually reproducing organisms, which are now called genes. These genes can be identical or different, leading to the expression of specific traits in offspring based on inheritance patterns.

• The Assertion is true. In Mendel's experiments, he found that the first-generation progeny all displayed the trait of one parent without any blending of traits. This observation led Mendel to propose the presence of two copies of factors controlling traits.
• The Reason is also true. Mendel's conclusion about the presence of two copies of factors controlling traits was based on his observation of the F1 progeny. He inferred that these factors (genes) existed in pairs in sexually reproducing organisms.
• Therefore, Option A is the correct answer as both the Assertion and Reason are true, and the Reason correctly explains the Assertion.

• Option A: (a) Gregor Mendel - Discovered the double helix structure of DNA:
  • Explanation: This is incorrect. The double helix structure of DNA was discovered by James Watson and Francis Crick, not Gregor Mendel. Mendel is known for his work on the inheritance of traits.
• Option B: (b) Free earlobe - Recessive trait:
  • Explanation: This is incorrect. Free earlobes are actually a dominant trait, while attached earlobes are recessive.
• Option C: (c) Attached earlobe - Dominant trait:
  • Explanation: This is incorrect. Attached earlobes are a recessive trait, not dominant.
• Option D: (d) Tall plant - Dominant trait:
  • Explanation: This is correct. In Mendel's experiments with pea plants, he found that the tall trait (T) is dominant over the short trait (t). Therefore, tall plants exhibit the dominant trait.

A plant's height is determined by the number of copies of the letter 'T'. If at least one 'T' is present, the plant will be tall, making 'T' the dominant trait in this scenario.

Traits like 'T' are called dominant traits, while those that behave like 't' are called recessive traits. Dominant traits are expressed when at least one dominant allele is present, whereas recessive traits are only expressed when an individual has two recessive alleles for that trait.

• Explanation: The assertion is true because in a heterozygous individual, the dominant allele will determine the phenotype.
• However, the reason is false because the dominant allele does not "mask" the recessive allele but rather is expressed over it.
• Therefore, the reason is not the correct explanation of the assertion.

• Objective: In the given explanation, a single copy of 'T' is enough to make the plant tall, indicating that 'T' is the dominant trait. For a plant to be short, both copies have to be 't', indicating that 't' is the recessive trait. Therefore:
• Option A: (a) TT - Tall, Tt - Short (Incorrect; Tt is also tall since 'T' is dominant)
• Option B: (b) TT - Short, tt - Tall (Incorrect; TT is tall and tt is short)
• Option C: (c) Tt - Tall, tt - Short (Correct; Tt is tall because 'T' is dominant, and tt is short because both are recessive)
• Option D: (d) TT - Tall, tt - Tall (Incorrect; tt is short, not tall)
• Hence, the correctly matched pair is Tt - Tall, tt - Short, making Option C: (c) the correct answer.

New combinations of traits in the F2 offspring are formed through the processes of random assortment and independent assortment of genes. This means that traits are inherited independently of each other, leading to diverse combinations beyond what was seen in the parent generation.

Cellular DNA serves as the information source for creating proteins within the cell. Proteins play crucial roles in various cellular functions, making them essential components for biological processes.

• The Assertion is correct as new combinations of traits indeed arise in F2 offspring due to the recombination of factors controlling seed shape and color.
• The Reason is also correct as the statement accurately reflects the independent inheritance of the tall/short and round seed/wrinkled seed traits.
• However, the Reason does not provide a direct explanation for the Assertion. While both statements are true, they are not intricately linked in a cause-and-effect relationship, leading to Option B being the correct answer.

The sex of an individual in human beings is largely genetically determined, based on the genes inherited from parents. This genetic inheritance decides whether an individual will be male or female.