Question

Choose the correct answers from the alternatives given :
During prophase I of meiosis homologous chromosomes pair with each other to form bivalents A bivalent is an association of

• A. two chromatids and one centromere
• B. four chromatids and two centromere
• C. two chromatids and two centromere
• D. four chromatids and four centromere

Answer 1

The correct option is B four chromatids and two centromere

• During the leptotene stage of the prophase 1 of the meiosis 1 the chromosomes are condensed and they start to form pairs.
• The homologous chromosomes that pair are called sister chromatids.
• Each pair of chromosomes have 2 chromosomes which are similar to each other. They are connected to each other by the means of centromere which is present in the middle of the chromosomes and are also called primary constriction.
• Bivalents mean that structure has 2 pairs of homologous chromosomes. Which means that each pair has 2 sister chromatids which is each connected by a centromere.
• Therefore the whole structure is made up of 4 chromatids ( 2 pair of sister chromatids) and 2 centromere each present in 1 pair.
• Therefore the correct answer is option 'four chromatids and two centromere'.