Genetic Aberrations (6) Flashcards
What are genetic aberrations caused by?
Genetic aberrations are caused by mutations.
What is a mutation?
A mutation is any alteration in the genetic makeup (genetic code) of an organism.
Factors that lead to genetic changes (changes in the sequence of nucleotides) during a lifetime may be caused by: (2)
- One or more nucleotides being damaged or lost by chance:
- crossing over of paternal and maternal chromosomes in meiosis
- replication of DNA
- transcription of DNA to RNA. - Breakdown of DNA by mutagens, e.g
- environmental factors such as sunlight, radiation and smoking
- mutagenic chemicals (e.g. formaldehyde, benzene, carbon tetrachloride)
- viruses and microorganisms.
Define mutagen.
Physical or chemical agents that induce and speed up mutations in DNA
What are gene mutations?
Gene mutations are small, localized changes in the structure of DNA strands.
Changes that involve a single nucleotide are called point mutations. They may occur by (3)
- substitution - where one nucleotide is exchanged for another.
- insertions- where one or more extra nucleotides are added to the DNA molecule.
- deletions- where one or more nucleotides are removed from the DNA molecule.
When the sequence of nucleotides is ____, individual codons are affected, altering the mRNA transcribed from the ____ DNA. This causes the absence of or incorrect form of the protein for which that gene codes.
altered
mutated
One of the ways that DNA technology can be applied is in DNA ____ or ________.
profiling
fingerprinting
Each person has unique DNA (except for identical twins), despite the fact that ____ of human DNA is identical. The differences occur in the highly variable, non-coding part of DNA.
99.9%
What does DNA profiling involve?
DNA profiling involves the extracting and identifying the highly variable regions of a person’s DNA that contain repeating sequences of base-pairs called STRS (short tandem repeats), e.g. CAGACAGACAGA is a repeat of CAGA three times.
What distinguishes one DNA profile from another?
At the same point in the DNA of different people, the number of repeated sequences of DNA base pairs varies considerably, OS distinguishing one DNA profile from another.
From 13 to 20 different sites on DNA molecules are investigated; enough to show that an individual’s profile is ____. Scientists can use these repeated sequences that vary to generate a DNA profile of an individual, using samples from ____, bone, hair and other body tissues and products.
unique
blood
DNA profile=
an individual’s unique DNA fragments, separated by electrophoresis.
How is a DNA profile made? (5)
- The cells are treated with chemicals to extract the DNA.
- Restriction enzymes are used to cut at the beginning and end of each repeated sequence, resulting in fragments of different lengths.
- Through a complicated process known as Polymerase Chain Reaction or PCR, large numbers of these fragments are made to provide a substantial amount of DNA to work with.
- The DNA fragments that result are then separated and detected, using different techniques such as electrophoresis.
- In this way a pattern is obtained that reflects different numbers of base-pair repeat in different individuals; the length of a particular DNA fragment depends on the number of repeats present. These separated DNA fragments are represented as dark bands on a piece of film. This is a DNA fingerprint.
What is Polymerase Chain Reaction, or PCR?
a laboratory technique used to make multiple copies of a segment of DNA
