Outline the process of in vitro fertilization (IVF).

Identify the cell labelled X.

Outline the function of this cell.

Explain how meiosis results in genetic variation in gametes.

mother receives hormone treatment/FSH to stimulate egg development;
eggs and sperm collected/harvested / eggs taken from ovary;
egg fertilized outside the body/in a dish/in a lab;
develops into embryo;
embryo(s) implanted (artificially) in mother’s body/uterus;
Do not accept egg/fertilized egg/zygote implanted.

Sertoli cell / nurse cell

nourishes maturing sperm(atozoa) / protects sperm from lymphocytes

crossing over in prophase 1/between chromatids;
random orientation of bivalents/homologous pairs in metaphase 1;
random orientation of chromatids/chromosomes in metaphase 2;

In vitro fertilization was understood well by many, though some answers were too vague to score some of the marks. The main area of misunderstanding was over what is put into the mother‟s uterus. Many candidates thought that it was fertilized eggs or zygotes and others thought that it was blastocysts. The latter was accepted as they are at least embryos, but much older than the stage usually implanted; embryos at the four cell stage.  

Many candidates were able to identify X as a Sertoli cell.

 Many candidates were able to identify X as a Sertoli cell, but not all could then state the function correctly.

This is a question that has often been asked but it is still an area that many candidates find difficult. Crossing over and independent orientation have sometimes been awarded marks in previous papers, if the terms are stated without any understanding of them being shown. In this paper the stage of meiosis was also required or some details of what the processes involve. As a result many candidates scored one mark only or none. Candidates should be encouraged to develop deep understanding of biological processes and not merely learn names; this will very much be the focus of the new IB Biology programme currently under development.