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VICBiologyQuick questions
Unit 2: How does inheritance impact on diversity?
Quick questions on Meiosis, crossing over and genetic diversity: VCE Biology Unit 2
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are the two meiotic divisions?Show answer
Meiosis consists of two consecutive divisions after one round of DNA replication. It produces four haploid daughter cells from one diploid parent cell.
What is crossing over (prophase I)?Show answer
During prophase I, homologous chromosomes pair up tightly (synapsis). Non-sister chromatids cross each other at chiasmata and exchange DNA segments.
What is independent assortment (metaphase I)?Show answer
At metaphase I, each homologous pair lines up at the equator independently of every other pair. The maternal homologue may face the "top" pole or the "bottom" pole, with equal probability, and each pair makes that choice independently.
What is errors in meiosis?Show answer
Non-disjunction: failure of homologous chromosomes (meiosis I) or sister chromatids (meiosis II) to separate. Produces gametes with the wrong chromosome number (n+1 or n-1). After fertilisation, this leads to aneuploidies like trisomy 21 (Down syndrome), XO (Turner) or XXY (Klinefelter).
What is interphase?Show answer
DNA is replicated in S phase. Each chromosome now consists of two identical sister chromatids joined at the centromere.
What is meiosis I?Show answer
Separates homologous chromosomes (one homologue to each daughter cell). Halves the chromosome number from 2n to n.
What is meiosis II?Show answer
Separates sister chromatids. Does not change chromosome number.
What is q1?Show answer
State two mechanisms that increase genetic variation during meiosis, and identify the phase at which each occurs. [2 marks]
What is q2?Show answer
A cell has chromosomes. Calculate the number of distinct gametes possible from independent assortment alone (ignore crossing over) and explain your method. [2 marks]
What is q3?Show answer
Refer to meiosis in mammals. (a) Distinguish meiosis I from meiosis II in terms of what separates. (b) Explain how non-disjunction at meiosis I can produce a trisomy.