Genetics Flashcards
What direction is DNA replicated in?
5’ to 3’
What phase of the cell cycle does DNA get replicated?
S phase
What is the amount of protein produced determined by?
- rate of transcription
- rate of splicing to mRNA
- rate of processing of polypeptide
What is a polymorphism?
a variation in the human genome with population frequency of greater than 1% or any variation that doesn’t cause disease but may predispose to a common disease
How many chromosomes does the normal human have?
46 including sex
What is the arm of a chromosome called?
telomere
What is an acrocentric chromosome?
a chromosome with one very short arm
What is unbalanced chromosome rearrangement?
there is an extra or missing chromosome
What is anueploidy?
a whole or extra missing chromosome
What is translocation?
rearrangement of chromosomes
What is Down syndrome caused by?
third copy of chromosome 21
What is a Robertsonian translocation?
two acrocentric chromosomes stuck end to end
What is Edwards syndrome?
an extra chromosome 18
Why is X chromosome aneuploidy sometimes not as bad?
due to X inactivation
What are the results of a large or a small translocation of DNA?
- large results in miscarriage
- small results in large child malformations
What is aCGH?
first line test which finds polymorphisms but doesn’t detect balanced arrangements
What is FISH used for?
to identify DNA segements
What is mosaicism?
being composed of cells of two genetically different types so there is two genetic makeups
What can somatic mosaicism contribute to?
for a chromosome abnormality it can contribute to cancer
How are individual DNA sequences analysed?
PCR and sequencing
What is next generation sequencing good for?
large scale cheap sequencing for a whole genome or exome
What is the non-coding part of DNA involved in?
regulation of genes
spaces genes out
insulates genes from promoters
What is c. for?
complementary or coding so effects the mRNA
What is p. for?
protein so affects the peptide chain
What does a change in the promoter or spice sequence do?
stops transcription or causes abnormal splicing
What is penetrance?
likelihood of having the disease if you have a mutation
What are Mendelian disorders?
segregate in families according to Mendel’s law
Why do females show some characteristics of X linked disease?
X inactivation
What type of disease is cancer?
a disease of mosaicism caused by post-zygotic mutations
What are the characteristics that cell acquire on the way to becoming cancerous?
- proliferation
- evading immune response
- acquiring vascular supply
- avoiding apoptosis
- metastasis
What are driver mutations?
drive carcinogenesis
What are passenger mutations?
incidental mutations that happen because the tumour is unstable
What is DNA methylation?
adding a methyl to a cytosine base leading to repression of transcription
What can methylation cause in cancer?
gene silencing
Why is the methylation of cytosine a problem?
it is then one deamination away from being a thymine which could be a series mutation
What are the characteristics of cancer determined by?
its driver mutations not by its tissue of origin
What things can a gene be activated by?
- duplication
- activation of gene promoter
- change in amino acid sequence
How can cancer be analysed?
by genetic sequence or by light microscpoy
What are the features of predisposition to cancer?
it is monogenic or multifactorial
