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Genetic Variations and Chromosomal Abnormalities: Lecture Notes, Exams of Advanced Education

Princeton UniversityAdvanced Education

A detailed overview of genetic variations, including constitutional variation, genetic mosaicism, single nucleotide variants (snvs), and structural variants. It covers the consequences of snvs, such as missense and nonsense mutations, and discusses disease heterogeneity and dominant negative missense mutations. The document also explains chromosomal abnormalities like aneuploidy, deletions, duplications, and translocations, including robertsonian and reciprocal translocations. Additionally, it addresses non-disjunction in meiosis and its effects, x chromosome inactivation, and examples of diseases caused by specific mutations, offering a comprehensive review of key concepts in genetics and genomics.

Typology: Exams

2024/2025

Available from 07/13/2025

Prof-Cornel
Prof-Cornel 🇺🇸

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MGY250 - Lecture 3 Test With
Complete Solution
Constitutional variation - Answer Genetic variation that is present in the genome of
every (or the vast majority of every) cell in an individual
Genetic mosaicism - Answer Condition in which regions of tissue within a single
individual have different chromosome constitutions.
Tissue specific
Example - Retinoblastoma
- Mutation in the eye - disease
True or false: Variants in the gremline are heritable but somatic mutation are not? -
Answer True
single nucleotide variants - Answer silent nucleotide change that occurs more often,
doesn't have a large effect
MAF > 1%
What are the 4 consequences of SNV? - Answer 1. Change in AA - missense
2. Introduction of a stop codon - nonsense
3. Alteration of a splice site
4. Alteration fo a splice enhancer
SNV can be: - Answer - Substitutions
- Deletions
- Insertion
True or false; different proteins have different tolerance for AA substitutions? - Answer
True
All mutations in ACTA1 are - Answer Pathogenic
Missense - Answer changes amino acid and changes the function of a protein
- depending on the impact of the AA change we can predict if the change will be
deleterious, depends on:
1. Alteration in AA size or charge
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MGY250 - Lecture 3 Test With

Complete Solution

Constitutional variation - Answer Genetic variation that is present in the genome of every (or the vast majority of every) cell in an individual Genetic mosaicism - Answer Condition in which regions of tissue within a single individual have different chromosome constitutions. Tissue specific Example - Retinoblastoma

  • Mutation in the eye - disease True or false: Variants in the gremline are heritable but somatic mutation are not? - Answer True single nucleotide variants - Answer silent nucleotide change that occurs more often, doesn't have a large effect MAF > 1% What are the 4 consequences of SNV? - Answer 1. Change in AA - missense
  1. Introduction of a stop codon - nonsense
  2. Alteration of a splice site
  3. Alteration fo a splice enhancer SNV can be: - Answer - Substitutions
  • Deletions
  • Insertion True or false; different proteins have different tolerance for AA substitutions? - Answer True All mutations in ACTA1 are - Answer Pathogenic Missense - Answer changes amino acid and changes the function of a protein
  • depending on the impact of the AA change we can predict if the change will be deleterious, depends on:
  1. Alteration in AA size or charge
  1. Highly conserved AA
  2. Functionally important part of the protein Dominant negative missense mutation - Answer Mutation interferes with the function of WT Example: ARG403Gln - cardiomyopathy
  • Mutation interferes with the dimerization of protein -> effecting normal function Disease heterogeneity - Answer Mutations in the same gene can manifest different diseases Example: Mutation in MYH7 can manifest either
  1. Muscular dystrophy
  2. Cardiomyopathy Recessive missense mutation - Answer Requires both mutant alleles Example: GD551D mutation in CFTR Nonsense mutation - Answer introduces a stop codon and initiates nonsense mediated decay and RNA degradation, causing a truncated protein Example: LMDO3 -> no protein expression - severe truncated protein
  • Formation - Answer a protein that does not achieve its full length or its proper form, and thus is missing some of the amino acid residues that are present in a normal protein. A truncated protein generally cannot perform the function for which it was intended because its structure is incapable of doing so Formation: If the mutation is in the last 2 exons - evades degradation splice site mutation
  • Can result in: - Answer Interfere with the processing of pre-mRNA, changes the way the RNA is spliced (introns cut out)
  • Can result in:
  1. Exon removal - dominant negative, frameshift, stop codon
  2. Intronic sequence (retention of intron 1) - stop codon Example: Ullrich congenital muscular dystrophy, benthlem myopathy

lost -karyotype has only 45 chromosomes -people with this are phenotypically normal but offspring might be unblanaced True or false, balanced Chromosomal abnormalitie do not affect offspring - Answer false Chromosomal abnormalities - Reciprocal translocation - Answer -occurs when 2 chromsoomes break and exchange chromosome pieces -no material genetic lost or gained so not typically associated with phenotypic abnormalities -produces unbalanced gamete -however offspirng may unbalanced Aneuploidy

  • Two types - Answer Abnormal number of chromosomes in a cell
  1. Autosomes
  2. Sex chromosome BCR-ABL (Philadelphia Chromosome) - Answer An abnormal chromosome produced by translocation of parts of the long arms of chromosomes 9(abl) and 22(bcr). -bcr and abl fuse -increased activity of abl -causes cancer non disjunction in meiosis 1 - Answer one cell gets both chromosomes and the other gets none in the second meiotic division 2 cells will have a set of chromosomes and 2 of them will have nothing if these cells fuse with another games during sexual reproduction 2 of the progeny will have a trisomy and the other 2 will have a monosomy Non-disjunction in Meiosis II - Answer depends on if only 1 of the cells have non-disjunction or if both of them do Ex. if one of them does it will result 1 abnormal diploid cell(with form a trisomy), 1 cell with no chromosomes(will form a monosomy), and 2 normal haploid gametes How X and Y pair in male meiosis - Answer share regions of homology PAR1 and PAR

When is a mutation deleterious? - Answer - alter amino acid shape or charge -> effect protein folding

  • mutation in a conserved amino acid
  • occurs in a functional part of the protien What type of mutation is Arg403Gln in MYH7 gene? - Answer Missense dominant negative MYH7 gene is an example of - Answer Disease heterogeneity P.Ala1636Pro mutation in MHY7 -> muscular dystrophy ARG403GLN mutation in MYH7 -> cardiomyopathy What is an example of a recessive missense mutation? - Answer GD551D mutations in CFTR gene If a nonsense mutation occurred in untranslated region - Answer No effect unless it affects gene processing If a nonsense mutation occurs at ATG site - Answer RNA decay If nonsense mutation occurs around 55 nuclear tides (NMD- free zone] - Answer Truncated protein - shortened protein Escapes decay Homozygous mutation in LMOD3 is an example of - Answer Nonsense mutation No protein expression Mutation vs polymorphism - Answer both are variants A mutation is defined as any change in a DNA sequence away from normal. -frequency < 0. -associated with disease

Polymorphism is a DNA sequence variation that is common in the population. -frequency > 0.01 in population -not associated with disease

Structural variant mutation - Answer Deletions, Duplications, rearrangements

Cri du chat syndrome - Answer Caused by a deletion in the short arm of chromosome 5

True or false; impact/severity of chromosomal deletion depends on - Answer Genes lost and function of lost genes

Why are Robertsonian translocations balanced? - Answer Considered balance because the short arms only had non-coding DNA, so there is no gene dosage imbalance as a result