Mutations and Genetic Analysis Flashcards
Name the three subtopics of chromosomal abnormalities.
Numerical
Structural
Mutational
Describe numerical chromosomal abnormalities.
The wrong number of chromosomes is present in a karyotype, not the normal number of 46.
Describe structural chromosomal abnormalities.
A large-scale rearrangement where chromosomes have fused, or gross change has taken place.
Describe mutational chromosomal abnormalities.
Smaller scale changes which are revealed through more detailed molecular approaches.
Define trisomy.
An extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities.
Why do numerical chromosome abnormalities occur?
Due to a failure of disjunction during meiosis.
What can happen in disfunction during meiosis?
Both of the homologs may end up in the same cell.
What happens if the sister chromatids fail to sperate at the second mitotic division?
Can result in diisomy where two sister chromatids end up in one of the gametes,
What is trisomy 21 better known as?
Down’s Sydrome
What increases the risk of Down’s sydrome?
An increase in maternal age.
Discuss some characterisations that individuals with Down’s syndrome may have.
-Characteristic facial dysmorphologies
-IQ less than 50
-Average life expectancy (50-60 years)
-Alzheimer’s disease in later life
What is the other name for trisomy 13?
Patau syndrome`
Name two features of Patau Syndrome
-Multiple dysmorphic features and mental retardation
-About 5% die within first month, very few survive beyond first year
What is the other name for trisomy 18?
Edwards syndrome
Describe the survival rates for those with Edward’s Syndrome.
Severe developmental problems; most patients die within first year, many within first month
When do sex chromosome aneuploidy syndromes occur?
When there’s an abnormal number of sex chromosomes.
What syndrome has 45 chromosomes and one X gamete?
Turner’s syndrome
Describe some features of those with Turner’s syndrome.
Females of short stature and infertile
Neck webbing and widely spaced nipples
Intelligence and lifespan is normal
Will individuals with Turner’s Syndrome be male, female or both?
Female as only one X chromosome
Which syndrome occurs in individuals with 47 chromosomes and the gametes XXY?
Klinefelter syndrome
Describe some features of those w Klinefelter syndrome
Tall stature, long limbs
Male but infertile, small testes, about 50% gynaecomastia
Mild learning difficulties
What can a structural abnormality involve?
-Balanced or unbalanced rearrangements
-Translocation mutation
-Deletion mutation
-Insertion mutation
-Inversion mutation
Name the two types of translocation.
Reciprocal
Robertsonian
Describe Robertsonian translocation
Fusion of two acrocentric chromosomes
Describe Reciprocal translocation.
Involving breaks in two chromosomes with formation of two new derivative chromosomes
What does balanced translocation look like?
Two completely different chromosomes which exchange large sections of information
-Same number of copies of all the original DNA are still presen
What will happen if a gamete inherits two normal chromosomes?
Gamete may inherit two normal chromosomes. If fertilised by a normal gamete, everything should be fine.
What will happen if a gamete inherits one chromosome w a balanced translocation?
Iif fertilised by a normal zygote, will probably result in a normal phenotype too despite the translocation.
What will happen if a gamete inherits one normal chromosome and another with an unbalanced chromosome?
The gametes will be unbalanced and do not have the normal complement of DNA. If fertilised by a normal gamete, there will still be an abnormal amount of DNA.
What happens in the Robertsonion translocation?
The information which is usually present on two different chromosomes is now on one.
What would happen if we have a Robertsonian translocation that involves chromosome 21 and 14?
Gamete formed in unbalanced.
If fertilized by a normal gamete, it may lead to trisomy 21 or trisomy 14.
How can large-scale deletions be caused?
Breaks forming in chromosomes.
If normal repair fails to happen, DNA material instead gets deleted resulting in a chromosome which has lost material.
How can inversions occur?
When a large piece of DNA is reversed.
-Usually balanced so doesn’t normally have a phenotypic effect.
Where can genetic mutations arise?
In the germ line or somatic cells.
What can gene mutations do?
Disrupt genes and bring about gene associated disease
What are polymorphism mutations?
Don’t have any phenotypic effect and no apparent differences but there are slight differences.
Name the two broad subtopics of mutation which might arise.
Coded
Non-coded
Describe non-coding DNA mutations.
Mutations and changes that take place in DNA that doesn’t directly code for protein but could have an effect if in a promoter region that’s involved in controlling the transcription of a gene.
What kind of coding mutations may there be?
Silent
Missense
Nonsense
Frameshift
Give an example of a silent mutation.
Synonymous (doesn’t change the amino acid coded for)
e.g. CGA (Arg) to CGC (Arg)
->has no effect as both sequences code for argenine
Give an example of a missense mutation.
CGA (Arg) to GGA (Gly)
->change from arginine to glycine which may have a major impact on the function of the protein.
Give an example of a nonsense mutation.
CGA (Arg) to TGA (Stop)
->TGA is a stop codon
Give an example of a frameshift mutation.
Insertion or deletion
Name some processes that can be used to detect mutations.
-Polymerase chain reaction (PCR)
-Gel electrophoresis
-Restriction fragment length polymorphism (RFLP) analysis
-Amplification refractory mutation system (ARMS)
-DNA sequencing
Is PCR in vivo or in vitro?
In vitro
What is required to do a PCR?
-Sequence information
-Oligonucleotide primers
-DNA
-Nucleotides
-DNA polymerase
What is the aim of PCR?
To amplify a region of DNA
Describe the steps of the Polymerase Chain Reaction.
Step 1- denature at 93-95 degrees
Step 2- anneal at 50-70 degrees
Step 3- Extend ay 70-75 degrees
Repeat process 20-30 times
Define the process of annealing relating to DNA
When the temperature is lowered to enable the DNA primers to attach to the template DNA.
What is used to extend the DNA during PCR?
Thermo resistant DNA polymerase
What process would you do after PCR?
Gel electrophoresis
Explain the purpose of gel electrophoresis
Separates DNA fragments by size.
Describe gel electrophoresis takes place.
Apply an electric field
DNA is negatively charged so will separate through agarose gel matrix and allows us to visualise DNA fragments
List some advantages of PCR
-Quick
-Easy to use
-Sensitive
-Robust
Name some applications of PCR.
-DNA cloning
-DNA sequencing
-In vitro mutagenesis
-Gene identification
-Gene expression studies
-Forensic medicine
-Typing genetic markers
-Detection of mutations
What is ARMS?
Amplification Refractory Mutation System
->a simple method for detecting any mutation involving single base changes or small deletions.
List some advantages of ARMS
-Cheap
-Labelling not required
-Electrophoresis required
-Primer design critical
List some disadvantages of ARMS
-Need sequence information
-Limited amplification size
What are restriction endonucleases?
Enzymes originally derived from bacterial cells which are biologically a protective mechanism to degrade the DNA of invading viruses.
Does the site in which restrictive endonuclease cut the DNA differ?
No, always cuts DNA at the same site.
What is RFLP analysis used for?
Finds where a specific gene for a disease lies on a chromosome
Name some advantages of RFLP analysis.
Simple
Cheap
Non-radioactive
List some disadvantages of RFLP analysis.
Requires gel electrophoresis
Not always feasible
What method does most DNA sequencing involve?
Involves the chain termination method
List some advantages of DNA sequencing.
-Gold standard for mutation detection
-Automation and high throughput
List some limitations of DNA sequencing
Expensive equipment
Poor quality sequence read
