QQuestionBiology
QuestionBiology
Which phrase best describes the process of crossing over?
A. Pairs of homologous chromosomes exchange segments.
B. Pairs of sister chromatids exchange segments.
C. Pairs of homologous chromosomes become linked.
D. Pairs of sister chromatids become linked.
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Answer
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Step 1:I'll solve this problem step by step, focusing on the biological concept of crossing over.
Step 2:: Understand the Terminology
Crossing over is a key genetic process that occurs during meiosis, specifically during prophase I of meiosis I. Let's analyze each option carefully.
Step 3:: Examine the Key Components
- Homologous chromosomes: Chromosomes that are similar in size, gene position, and centromere location, but may have different alleles - Sister chromatids: Identical copies of a chromosome created during DNA replication, still attached at the centromere
Step 4:: Analyze the Options
A. Pairs of homologous chromosomes exchange segments. - This is the CORRECT description of crossing over - During prophase I, homologous chromosomes pair up (synapsis) - Segments of these homologous chromosomes can physically exchange genetic material
Step 5:: Eliminate Incorrect Options
B. Pairs of sister chromatids exchange segments. - Incorrect: Sister chromatids are identical, so they do not exchange different genetic information C. Pairs of homologous chromosomes become linked. - Partially true, but does not describe the actual genetic exchange D. Pairs of sister chromatids become linked. - Incorrect: Sister chromatids are already linked at the centromere
Final Answer
Pairs of homologous chromosomes exchange segments.
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