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Multiple Choice
Which of the following best describes the homologies shared by rats and elephants with respect to their chromosomes?
A
Both lack homologous chromosomes because they are different species.
B
Both possess homologous chromosomes that carry genes for similar traits inherited from a common mammalian ancestor.
C
Both have identical chromosome numbers and identical DNA sequences.
D
Both have only sex chromosomes in common, with no other chromosomal similarities.
Verified step by step guidance
1
Understand the concept of homologous chromosomes: Homologous chromosomes are pairs of chromosomes that have the same structure and carry genes for the same traits, although the specific alleles may differ. These chromosomes are inherited from a common ancestor and are present in all sexually reproducing organisms.
Recognize that rats and elephants are both mammals: As mammals, they share a common evolutionary ancestor, which means they have homologous chromosomes that carry genes for similar traits, even though they are different species.
Clarify why the first option is incorrect: The statement 'Both lack homologous chromosomes because they are different species' is incorrect because homologous chromosomes are a fundamental feature of sexually reproducing organisms, regardless of species differences.
Explain why the third option is incorrect: The statement 'Both have identical chromosome numbers and identical DNA sequences' is incorrect because different species typically have different chromosome numbers and DNA sequences, even if they share homologous chromosomes.
Address the fourth option: The statement 'Both have only sex chromosomes in common, with no other chromosomal similarities' is incorrect because homologous chromosomes are not limited to sex chromosomes; they are present across the genome and carry genes for similar traits inherited from a common ancestor.