Genetics - 1 - Class 10 Free MCQ Test with solutions

To determine the proportion of dwarf progeny, we analyse the cross between a heterozygous tall plant (Tt) and a homozygous dwarf plant (tt).

Genotypes:

• Tall plant: Tt
• Dwarf plant: tt

When these plants are crossed, the possible genotypes of the progeny are:

• Tt (tall)
• Tt (tall)
• tt (dwarf)
• tt (dwarf)

From these genotypes, we see that:

• 2 out of 4 possible genotypes (50%) will be tall.
• 2 out of 4 possible genotypes (50%) will be dwarf.

Therefore, the proportion of dwarf progeny is 50%.

- A section of DNA that provides information for one protein is called a gene.

- A gene is a sequence of nucleotides in DNA that encodes the synthesis of a protein.

- Each gene contains the necessary instructions to build a specific protein, which plays a role in various cellular functions.

- Proteins are essential for numerous biological processes, including enzyme function, cellular structure, and signal transmission.

- The correct answer is B: Chromosomes.

- Chromosomes are structures within cells that contain a person's genes.

- Each chromosome is a long DNA molecule that carries part or all of an organism's genetic material.

- They are separate, independent pieces of DNA, distinct from one another.

- Genes are segments of DNA located on chromosomes.

- Nucleotides are the basic building blocks of DNA and RNA.

- Ribosomes are cellular structures that synthesise proteins and are not related to DNA structure.

- Human sex is determined by the presence of sex chromosomes.

- Females typically have two X chromosomes (XX).

- Males possess one X and one Y chromosome (XY).

- The father contributes either an X or a Y chromosome, which determines the child's sex.

- The mother always contributes an X chromosome.

- The sex of a human child is determined by the sex chromosomes inherited from the parents.

- Humans have two types of sex chromosomes: X and Y.

- The mother always contributes an X chromosome, as females have two X chromosomes (XX).

- The father contributes either an X or a Y chromosome, as males have one X and one Y chromosome (XY).

- If the child inherits an X chromosome from the father, the child will be female (XX).

- If the child inherits a Y chromosome from the father, the child will be male (XY).

Contributions to the success of Mendel:

• Knowledge of biology:

  - Mendel's background in biology helped him grasp the principles of inheritance and genetics.

  - His understanding of plant reproduction enabled him to conduct experiments and make precise observations.

• Qualitative analysis of data:

  - He carefully collected and examined data from his experiments.

  - By focusing on qualitative traits, like flower colour or seed texture, he identified clear patterns of inheritance.

• Observation of distinct inherited traits:

  - Mendel studied traits that were easily distinguishable, such as tall vs. short plants.

  - This selection allowed him to track inheritance patterns and make accurate predictions.

• Consideration of one character at a time:

  - Mendel concentrated on one trait per experiment, such as flower colour.

  - This approach helped him establish clear inheritance patterns without confusion.

Mendel's success stemmed from his biology knowledge, qualitative data analysis, distinct trait observations, and focusing on one character at a time. These factors were crucial in his groundbreaking discoveries in genetics.

Reasons why pea plants were more suitable than dogs for Mendel's experiments:

• Pea plants can be self-fertilized:
  • Pea plants possess both male and female reproductive organs, enabling self-fertilisation.
  • This feature allowed Mendel to control breeding and ensure the traits he studied were passed on.
• Dogs have many genetic traits:
  • Dogs display a wide variety of genetic traits, complicating the isolation of specific traits.
  • Mendel required a species with clear and contrasting traits, which pea plants provided.
• There are no pedigree records of dogs:
  • During Mendel's time, pedigree records for dogs were unavailable.
  • Pea plants were easier to track and study due to their simple genetic structure.
• The pea plants favour cross-fertilisation:
  • Pea plants naturally undergo cross-fertilisation, transferring pollen between plants.
  • This allowed Mendel to intentionally cross-pollinate plants with different traits, revealing predictable inheritance patterns.

Mendel chose pea plants for their ability to self-fertilise, distinct traits, available records, and natural cross-fertilisation, making them ideal for his studies on inheritance.