In eukaryotes, much of the nuclear DNA does not code for polypeptides. There are, for example, introns within genes and multiple repeats between genes. Differences in base sequences of alleles of a single gene may result in non-functional proteins, including non-functional enzymes.
Genetic comparisons can be made between different species by direct examination of their DNA or of the proteins encoded by this DNA. Comparison of DNA base sequences is used to elucidate relationships between organisms.
DNA sequencing and the PCR are used to produce DNA probes that can be used to screen patients for clinically important genes. The use of this information in genetic counselling e.g. for parents who are both carriers of defective genes and, in the case of oncogenes, in deciding the best course of treatment. Explain why scientists might use genetic fingerprints, in the fields of forensic science, medical diagnosis, animal and plant breeding.
Outline the steps involved in sequencing the genome of an organism. Outline how gene sequencing allows for genome-wide comparisons between individuals and between species.
Explain the uses of genetic screening; identification of carriers, preimplantation genetic diagnosis and prenatal testing (amniocentesis and chorionic villus sampling) and discuss the implications of prenatal genetic screening. Identify and discuss the social and ethical issues related to genetic screening from a range of ethical implications.
Explain how a phenotype is the result of an interaction between genotype and the environment (e.g. animal hair colour, human height, monoamine oxidase A and cancers), but the data on the relative contributions of genes and environment is often difficult to interpret.
Genetic and environmental factors produce variation between individuals.
The Human Genome Project has been used to locate and sequence alleles on human chromosomes.The potential uses and abuses of this knowledge. Possibility of automated routine screening for particular predisposing genes. Ethical issues surrounding this knowledge and gene ownership. Genetic fingerprinting of an individual produces a unique pattern of bands of DNA. Gene amplification, PCR. Uses of this technique and associated issues.
SQA Higher Biology
Unit 1 – d) Synthesis and Release of Proteins
The role of DNA, RNA and cellular organelles.
- i) The functional variety of proteins.
- ii) DNA: structure, in particular the double helix, nucleotides and bases; pairing of named bases; genes as regions of chromosomal DNA; the process of DNA replication and its importance.
- iii) RNA: single strand structure; replacement of thymine with uracil and deoxyribose with ribose; mRNA transcription; functions of mRNA and tRNA in synthesis of proteins; triplet code; codons and anticodons.
SQA Advanced Higher Biology
Unit: Cellular and Molecular Biology – Applications of DNA technology
- i) The Human Genome Project. Genetic linkage mapping. Location of genetic markers to allow testing of genetic linkage to known markers. Physical mapping. Determination of order of genes on each chromosome. DNA sequencing. Determining the order of nucleotide pairs of each chromosome. Analysing the genomes of other species. Comparison of the human genome with other species reveals remarkable similarities.
- ii) Human therapeutics. Detecting genetic disorders.
- iii) Forensic uses.
Interaction of genes and the environment produce the phenotype. Twin studies show the effects of genes and environment.
The human genome has been sequenced. The DNA nucleotide sequences have been determined. This does not translate into a list of genes coding for proteins. There is non-coding DNA. There are regulatory genes. Determining the genome of simpler organisms allows the proteome of the organism to be determined. This may allow vaccines to be produced against pathogens.The work of the Sanger Institute in producing a vaccine against Plasmodium.
Outline how the Human Genome Project has enabled the sequencing of human DNA and describe the possible uses of this information.
Describe the role of the genetic counsellor.Discuss the ethical issues involved in the work of the genetic counsellor.
About this resource
This resource was first published in ‘Genes, Genomes and Health’.