Question

Based on the ideas proposed by Morgan, which of the following statements concerning linkage is false? a. Traits determined by genes located close together on the same chromosome are likely to be inherited together. b. Crossing over between homologous chromosomes can create new allele combinations. c. A crossover is more likely to occur in a region between two genes that are close together than in a region between two genes that are farther apart. d. The probability of crossing over depends on the distance between the genes. C. Genes that tend to be transmitted together are physically located on the same chromosome.

Short answer

The false statement is c. A crossover is more likely to occur in a region between two genes that are close together than in a region between two genes that are farther apart.

Step-by-step solution

Understanding Linkage and Morgan's Observations

Genetic linkage is a term used in genetics to refer to the phenomenon where certain genes tend to be inherited together because they are located on the same chromosome. Morgan's observations, albeit in a simplified summary, indicated that: \n1. Genes that are close together on the same chromosome are more likely to be transmitted together (linkage). \n2. Crossing over between homologous chromosomes can lead to new combinations of genes (recombination).\n3. The probability of crossing over (and hence, recombination) depends on the distance between genes - the farther apart two genes are, the more likely a crossover will occur.

Evaluating Each Statement

Now, let's evaluate each statement one by one:\na. This statement is true according to Morgan's observations. Traits determined by genes located close together on a chromosome are more likely to be transmitted together due to linkage. \nb. This statement is also true. Crossing over between homologous chromosomes can result in new combinations of alleles - this is genetic recombination.\nc. This statement is false. According to Morgan's observations, a crossover is less likely to occur in a region between two genes that are close together and more likely to occur in a region between two genes that are farther apart.\nd. This statement is true. The probability of crossover does depend on the distance between genes - the farther apart two genes are, the more likely a crossover will occur.\ne. This statement is true as genes that tend to be transmitted together are physically located on the same chromosome.

Identify the False Statement

After evaluating each statement based on our understanding of genetic linkage and Morgan's observations, we found out that statement c is the false one. This statement contradicts Morgan's observations that a crossover is less likely to occur between two genes that are close together.

Key concepts

Crossing Over

Crossing over is a critical process in genetics where sections of DNA are exchanged between homologous chromosomes. This occurs during meiosis, the type of cell division that produces gametes like sperm and eggs.
During crossing over, chromosomes pair up and exchange segments of their genetic material. This leads to genetic variation, which is vital for evolution.

• It allows for new combinations of alleles, which are different versions of genes, on each chromosome.
• This shuffling contributes to the unique genetic makeup of each individual, even among siblings.

Crossing over has great significance in the study of genetic linkage. Genes that are close together on the same chromosome are less likely to be separated by crossing over. Hence, they tend to be inherited together, unless recombination occurs to break this linkage.

Recombination

Recombination is the process by which genetic material is shuffled to create new combinations of genes. This can happen due to crossing over during meiosis or other forms of genetic manipulation.
Recombination is essential for genetic diversity, allowing organisms to adapt to changing environments.

• It results in offspring having combinations of traits that differ from either parent.
• Through recombination, beneficial mutations can be shuffled together, potentially leading to advantageous traits.

Geneticists can use recombination frequencies to map out genes on chromosomes. By examining how often recombination occurs between gene pairs, researchers can infer the physical distance between genes on a chromosome. A higher frequency of recombination indicates a greater distance between genes, which is useful for creating linkage maps.

Thomas Hunt Morgan

Thomas Hunt Morgan was a pioneering figure in genetics who provided the first solid evidence for the chromosomal theory of inheritance. Working mainly with fruit flies (Drosophila melanogaster), Morgan made groundbreaking discoveries about genetic linkage and recombination.

• He observed that certain traits tend to be inherited together, leading him to propose the idea of genetic linkage.
• Morgan's experiments with fruit flies demonstrated that the likelihood of crossing over increases with distance between genes on a chromosome.
• He was awarded the Nobel Prize in Physiology or Medicine in 1933 for his discoveries concerning the role chromosomes play in heredity.

Morgan's work laid the foundation for modern genetics, enabling scientists to understand and predict genetic phenomena. His findings are integral to both basic genetics and practical applications, such as breeding crops with desirable traits or understanding hereditary diseases.