Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Gel Electrophoresis: A technique used to separate DNA fragments or proteins based on their size and charge. Since DNA is negatively charged due to the phosphate groups (), fragments migrate towards the positive electrode (anode).
PCR (Polymerase Chain Reaction): A method used to amplify small quantities of DNA. It involves three stages: Denaturation at , Annealing at , and Extension at using the heat-stable enzyme Taq DNA polymerase.
DNA Profiling: Comparison of DNA samples using Short Tandem Repeats (STRs). The number of repeats varies between individuals, creating a unique pattern of bands on a gel.
Genetic Modification: The transfer of genes between species, made possible by the universality of the genetic code. It requires restriction endonucleases to cut specific sequences (leaving 'sticky ends') and DNA ligase to join the sugar-phosphate backbone.
Somatic Cell Nuclear Transfer (SCNT): A method of cloning where the nucleus of a differentiated diploid () somatic cell is transferred into an enucleated egg cell, which is then stimulated to divide into an embryo.
Clones: Groups of genetically identical organisms, derived from a single original parent cell. Natural examples include binary fission in bacteria and runners in plants ().
📐Formulae
💡Examples
Problem 1:
A scientist starts a PCR reaction with a single double-stranded DNA molecule (). Calculate the total number of DNA copies produced after cycles.
Solution:
Explanation:
In each cycle of PCR, the number of DNA molecules doubles. Using the formula , where is the number of cycles, we find the exponential growth of the target sequence.
Problem 2:
In a paternity test gel electrophoresis, a child's DNA profile shows five distinct bands. Two bands match the mother's profile. What is the requirement for the remaining three bands?
Solution:
The remaining three bands must align perfectly with the biological father's DNA profile.
Explanation:
Because a child inherits half of their nuclear DNA from each parent, every band in the child's DNA profile that does not originate from the mother MUST have a corresponding match in the biological father's profile.