This page contains resource questions and discussion points designed to further conversation on the subject of aneuploidy and related biotechnologies used for genetic screening.
1. The diagram on the right is a human karyotype, containing 22 pairs of homologous chromosomes and the sex chromosomes.
a. Is this a male or a female karyotype?
b. Explain what homologous chromosomes are and what information they contain.
c. Define the term chromatin.
d. Describe the structure of a chromosome and explain the difference between chromatids and chromosomes.
2. Explain the difference between a gene and a chromosome mutation.
3. Cystic Fibrosis and Huntington’s disease are examples of inherited conditions caused by gene mutations. Cystic Fibrosis has an autosomal recessive inheritance pattern while Huntington’s Disease has an autosomal dominant inheritance pattern. Describe the difference between these inheritance patterns and explain how these differences impact on the likelihood of inheritance of the disease by the child of a carrier parent.
4. Define the term aneuploidy and explain the difference between monosomy and trisomy.
5. The diagram on the right shows the process of meiosis. Aneuploidy can be caused by non‐disjunction during meiosis, leading to the formation of gametes that are (n+1) or (n‐1). Explain how this occurs.
6. What is the difference between pre‐natal screening and pre‐natal diagnosis?
7. Pre‐natal diagnosis of chromosomal abnormalities uses karyotyping. In pre‐implantation genetic diagnosis karyotype testing is not an option because only one or two cells are collected and the chance of the chromosomes being visible is very slight. At what stage in the cell cycle are the chromosomes visible?
| Allele | Amniocentesis | Aneuploidy |
| Anneal | Autosomal dominant | Autosomal recessive |
| Autosome | Blastocyst | Byopsy |
| Chromatid | Chromatin | Chromosome |
| Chromosome mutation | Chronic villus testing | Comparative genomic hybridisation |
| Diagnosis | Embryo | Fetus |
| Fluorescence in situ hybridisation | Gamete | Gel electrophoresis |
| Gene | Gene mutation | Genetic counselling |
| Homologous | In vitro fertilisation | Karyotype |
| Ligation | Meiosis | Mitosis |
| Monosomy | Non-disjunction | Oocyte |
| Placenta | Polymerase chain reaction | Polyploidy |
| Pre-implantation genetic diagnosis (PGD) | Pre-implantation genetic haplotyping | Pre-natal/antenatal |
| Restriction enzymes | Saviour siblings | Screening |
| Semen | Sex chromosome | Spermatozoa |
| Translocation | Trimester | Trisomy |
| Ultrasound scan | Zygote |
Aspects of reproductive technologies offer good potential as topics for this achievement standard. When selecting a topic you are looking for an issue which will meet the following criteria:
While the use of reproductive technologies such as IVF are reasonably widely accepted in society, advances in reproductive technologies that have led to the availability of pre‐implantation genetic diagnosis offer potential as a topic for this achievement standard. Issues around decision relating to when PGD should be used and how it should be made available would offer a good starting point for the standard. A discussion around identifying where this technology is appropriate would be very interesting. The use of PGD to create saviour siblings is a particular aspect of the issue that would make an interesting topic for this standard.
