Genetics - Genetic Variation and how it causes Diseases Flashcards
What does SNP stand for?
Single Nucleotide Polymorphisms. Slide 2.40
What would the chances of a female carrier’s children have?
Half of male children will be affected, half of female children will be carriers. Slide 2.27
What are the temperature cycles of PCR?
100, 50, 72. Slide 18-22
What are the ways a child can get mutations?
- If one parent has a mutation
- No parents have it, new mutation occurs in gametogenesis
- One parent is mosaic
- Mutation is post-zygotic. Slide 57
Why might a carrier female show mild features of the disease?
Due to only one X chromosome is active, so some affected genes might be turned off and some normal ones might be randomly inactivated. Slide 2.30
What is a multifactorial disease?
When more than one environmental or genetic factors influence the disease. Slide 2.55
What is usual about common disorders?
They have a rather small effect but are very common. Slide 2.56
What are CNVs?
They are extra or missing stretches of DNA. Slide 2.49
What do SNPs do?
Most have no effect, some that do are expected to have smaller effects than a rare disease causing mutation and some completely destroy the gene without causing disease. Slide 2.48
What is a mutation?
A genetic variation that causes a disease. Slide 11
What is X linked recessive?
When the gene fault lies on the X chromosome. Slide 2.25
What would the chances of an affected male’s children have?
All male children would be normal, all of female children would be carriers. Slide 2.27
Are all females who carry a faulty gene on their X chromosome affected?
No, due to X inactivation, they are often a carrier but not affected. Slide 2.25
Where is mitochondrial DNA inherited from?
The maternal side. Slide 2.76
What are the pedigree drawing basic symbols of male, female, affected and not, miscarried and dead?
Male - box Female - circle Affected - coloured Unaffected - white Miscarried - Triangle Dead - Line through shape. Slide 2.9
What does autosomal dominant mean?
If you have the mutation then you’ll have the disease with 100% penetrance. Slide 2.11
What happens when there are mutations in a gene before a stop codon?
A stop codon may be kept in by accident and will cause it to be finished early so the protein will be short or absent. Slide 40
What is each temperature for in PCR?
100 - denature DNA strands
50 - for primers to bind
72 - optimum temp. for taq. polymerase to replicate. Slide 21
What are the 4 types of Mendelian Inheritance?
Autosomal Dominant
Autosomal Recessive
X linked
Mitochondrial. Slide 2.5
What happens when there are mutations in a gene between exons and introns?
An intron my be left in or a exon may be left out of the mature mRNA. That creates an abnormal or absent proteins. Slide 39
What is common about Mendelian disorders?
They have a big effect but are very rare. Slide 2.56
Can different mutations have different effects on the protein produced and can they be predicted?
Yes. Slide 2.17
What happens when the promotor has a mutation?
There is no or reduced transcription, therefore there are no or reduced protein. Slide 38
In a ‘rare’ genetic disorder, what has more of an impact to the genetic disorder; genotype or environment?
Genotype (single mutation). Slide 2.36
What is penetrance?
It is the likelihood of having a disease if you have the gene mutation. E.g. 100% penetrance means you will always have the disease if you have the mutation. Slide 2.3
What is autosomal recessive?
When there are 2 faulty copies of the gene to cause disease. 25% chance of parents having an effected child. Slide 2.20+2.21
What percentage of the genome are exons?
2-3%. Slide 8
Can different mutations in the same gene can cause the same disease?
Yes. Slide 2.17
What does CNVs mean?
Copy Number Variations. Slide 2.49
What ways does X inactivation come about?
So a gene dosage compensation can be provided.
Some genes on the pseudoautosomal region escape inactivation.
The XIST gene at Xq13 is essential to inactivate X.
Methylation is one mechanism of X inactivation. Slide 2.32
If more than half of the female carrier’s cells have the normal chromosome randomly inactivated, what happens to the phenotype of the female?
Her features from the disease will be much more prominent as there are more affected cells working. Slide 2.31
What are Mendelian Disorders
A disease that is predominantly cause by a change in a single gene (high penetrance) and segregate in families in the manner predicted by Mendel’s Laws. Slide 2.4
If the father was affected in X linked inheritance, why would the male offspring be normal?
There is no male to male transition, mothers provide the x chromosome for males. Slide 2.27
