Genetics Flashcards
Inheritance of duchenne muscular dystrophy
X-linked recessive (mostly)
anticipation (genetics)
a genetic disorder is passed on to the next generation, the symptoms of the genetic disorder become apparent at an earlier age with each generation.
uniparental disomy
when a person receives two copies of a chromosome, or of part of a chromosome, from one parent and no copy from the other parent
what is p and q on a chromosome?
p is the small arm and q is the larger one
what is the difference between chromosome and chromatid
chromosome includes the whole thing when it undergoes mitosis but the there are 2 chromatids
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cell cycle
Interphase (cells spends majority of time interphase):
- G1
- Making more organelles, mRNA, histones, increasing the volume of the cytoplasm
- S
- Chromosome duplication
- G2
- Cell with duplicated chromosomes
MItosis
What happens at metaphase in mitosis
The chromosomes are attached to the spindle fibres and lined up (46 chromosomes but 92 chromatids)
What is a tetra in meiosis
the homologous chromosomes from the mother and father that line up
What are the difference between bases in DNA vs RNA
DNA is guanin,e cytosine, adening, thymine
RNA is guanine, cytosine, adenine, uracil
Which direction is DNA synthesised
5’ to 3’
What bases are purine and what are pyrimadine
Pyrimadine = C, T, U
Purine = A, G
what are the 2 strands in DNA and which one is copied to mRNA?
Coding and template
The template strand is copied to make the mRNA version of the coding DNA strand
How is pre-mRNA modified to make mRNA?
- Capping - protects mRNA from degradation and ais in ribosome binding during translation
- poly (A) tail (made by polyA polyerase) - initiates translation
- Splicing (of the introns)
Role of microRNA
To regulate protein production
When the RNA precursor folds upon itself and is chopped up by a dicer and joins onto a protein complex
Binds onto target mRNA to either degrade mRNA or blockage translation
What is redundancy?
That there are more combinations of codons than amino acids
(including 3 stop codons)
In redundancy, what position of nucleotide is normally different? (but still coding for the same AA)
The 3rd nucleoside
What is the mechanism of trinucleotide repeat
Slipped-strand mispairing
- What is a missense mutation?
- What is a nonsense mutation?
- Missense
- A substitution in 1 DNA base pair that change the codon for 1 amino acid into another
- Nonsense
- When the DNA base change results in a stop codon - depends on where in the AA the codon is
What is epistasis (genetics)
When 1 gene affects the expression of another gene (e.g. albinism)
What happens when an oncoene is translocated next to an immunoglobulin heavy or light chain or T-cell receptor gene?
The T-cell receptor/Ig genes naturally undergo extensive rearrangements so that that oncogene can also undergo unregulated rearrangement and growth
(e.g. the heavy Ig gene is on chromosome 14 and a lot of haematological malignancies involve translocations with chromosome 14)
E.g. Mantle cell lymphoma 11:14 - translocation of the cyclin D gene onto the heavy Ig
What happens when there is Robertsonian translocation
When chromosomes with very short arms are lost.
Parents are generally not affected but the offsprings can have trisomy/monosomy
What stage of cell division is karyotype done at?
Metaphase
What does comparative genomics hybridization detect?
- Smaller regions of DNA along the lengths of all of the chromosomes
- CNVs
- Doesn’t detected balanced structural rearangements
What is loss of heterozygosity?
Loss of 1 allele’s DNA
(e.g. loss of normal gene in mutated cancer susceptibility gene
What is a Barr body?
An inactivated X chromosome
What is the mechanism of imprinting?
DNA methylation of the promotor region
What genetic phenomenon can cause haemophilia to manifest in females?
Skewed X-inactivation
What is the mechanism of uniparental disomy in meiosis?
Meiosis I - non disjunction
Meiosis 2 - when 2 games with x1 and x2 chromosome fuse, there is trisomy rescue where the 3 chromosomes are reduced to 2 and if the outcome combination are x2 chromosomes from 1 parent OR when there is monosomy rescue
Can unmask imprinting or develop recessive condition
How to calculate the carrier frequency from allele frequency?
Carrier frequency = 2pq as per the Hardy Weinberg Equation