Genetics Flashcards
What are coding and non coding portions of genes called
Coding- Exons
Non coding- introns
Which base pairs are purines and which are pyramidines
What is different about RNA
Purines- A and G (earlier in alphabet)
Pyrimidines- T and C
u instead of T
What are telomeres
Ends of genes- stop codons to prevent genes getting lost in replication
What is unique about mitochondrial DNA (2 things)
Circular
Only present in Eggs so only maternally inherited
Mitosis
What is it
What are the stages
What is formed at the end
Division of normally growing cells
Interphase- genetic material doubles Prophase- chromosomes pair up Metaphase- line up and spindles attach Anaphase- chromatids pulled apart Telophase- chromosomes line up at each pole. Cell divides into to
2 identical daughter cells- DIPLOID
Meiosis
What is it
What are the stages- what is different to mitosis
What forms at the end
Formation of egg and sperm
Mitosis one and PMAT2. No interphase 2
4 identical daughter cells which are all HAPLOID
What three things can go wrong in mitosis
What can go wrong in meiosis
Mitosis- insertions deletions and single nucleotide substitutions
Meiosis- non dysfunction
What is the usual gene issue in CF
What happens in a non sense mutation
Mid sense mutation- different amino acid forms- glutamine changes to valine
A non functional protein occurs
What is a robertsonian translocation
What types of chromosomes are involved? What are they? Which ones?
Does it affect the offspring and carrier equally
Give an example
Unbalanced translocation- p arm is lost
Acrocentric ch- centromere is near the end- 14,13,15,21&22
Won’t affect the individual, their offspring are likely to have issues
14:21- 1:8 chance of t21
What is imprinting
What causes an imprinting disorder
What is the normal and abnormal imprinting in: Prader willi Beckwith widemann Russel silver Angelman
Which chromosomes do the above involve?
Normal deletion (methylation) of a gene depending on who it’s inherited from Disorder= deletion of the active parents gene or UPD of the inactive
Prader willi- normal- maternal deletion. Defect is paternal deletion or maternal UPD ch15
BW- ‘ ch 11
Russell silver- normal is maternal deletion. Disease usually only maternal UPD. Ch7. Rarely can be paternal deletion ch 11
Angelman- normal- paternal deletion. Defect is maternal deletion- ch15 or paternal UPD- UBE3A
What is gene expression
What are the three stages
Turning a gene into a polypeptide (protein or enzyme)
1- transcription- turn DNA to mRNA- RNA polymerase reads from 3-5 and adds matching base pairs (u substitutes for t)
2- processing- non coding regions removed by splicing
3- translation- ribosome moves along mRNA 5-3. T RNA adds base pairs. Stops at stop codon and releases protein
How do you calculate incidence from carrier frequency?
(Carrier frequency squared) x 4
What does FISH look for
What are the two types of microarray available? Which finds consanguinity?why? Which shows more mosaicism?
Known microduplications or deletions
CGH- finds mosaicism up to 15%.
SNP- finds to 7%. Finds long stretches of homozygosity- consanguinity
What tests are used in whole genome sequencing to find:
RNA
DNA
Protein
Northern blot
Southern blot
Proteins
When is NIPT done?
What is the most likely cause of a false positive?
First trimester
Confined placental mosaicism
What will a microarray not find
Give an example
Balances Karyotypes
Triploidy
Autosomal dominant
What are the rules of transmission. If 1 parent has it what is the risk to offspring?
Can have male to male transmission
Equally affects men and women
50% chance of boys or girls having it
Autosomal recessive
What are the rules of transmission
If a sibling has it what does this mean
What is the risk to offspring if 1 parent has the disease
Equally male and female
2/3 chance siblings are carriers. Both Parents have to be carriers
All children are carriers
X linked recessive
What is the rule
If mum is a carrier what does this mean?
“If dad is affected
No male to male transmission
50% daughters are carriers, 50% sons affected. Rest normal
All daughters are carriers, no sons are affected
X linked dominant
Give 2 examples of conditions
What are the rules
Incontenenti pigmenti, Rett syndrome
Lethal in males
Same as XLR
Mitochondrial
What are the rules
Only mum can transmit it. All her children will be affected
Which triplet repeats are seen in: Myotonic dystrophy Friederichs ataxia Huntington’s Fragile x
What is unique about the anticipation seen in Huntington’s and MD
Md- CTG
FA- GAA
Huntington’s- CAG
Fragile X- CGG
Huntington’s shows anticipation with paternal inheritance, MD with maternal
Which locus is associated with low IQ
15q11.2
What three things can exon sequencing not pick up
Balanced things! Triplet repeats Mitochondrial Imprinting Balanced translocations
