281 lec28 2019 - hasan alhaddad genetics...
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Lecture 28:
Chromosomal mutations
Course 281
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Lessons for life
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AIMS
• Understand the mutations on a chromosomal level.
• Understand the different types of chromosomal mutations.
• Understand the consequences of chromosomal mutations and compare them to point mutations.
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MutationsMutation types
Point mutationChromosomal mutation
• Chromosomal mutations: are mutation that involve changes to the entire chromosome or sections of it. Also called segmental mutations.
• Chromosomal mutations are deviations from the normal condition of a chromosome both in structure and number.
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Chromosomal mutationsChromosomal mutations
Chromosome number mutations
Chromosome structure mutations
• Chromosome structure mutations: mutations that changes the amount of DNA in a chromosome or the orientation of the DNA within a chromosome.
• Chromosome number mutation: mutations that changes the number of chromosomes in a cell.
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Chromosomal structural mutationsChromosomal mutations
DNA orientation in a chromosome
Chromosome structure mutations
DNA content in a chromosome
Deletion Duplication Inversion Translocation
Let’s focus on the chromosomal mutations that are associated with DNA content
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Chromosomal deletion
• Deletions reduce the amount of DNA of a chromosome compared to the normal chromosome.
• Small deletions are less harmful than large deletions.
• Consequences of deletions depend on the genes lost.
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Chromosomal deletion
• Example:
• Williams syndrome
• Wolf-Hirschhorn syndrome
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Chromosomal deletion
Wolf-Hirschhorn syndromeWilliams syndrome
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Chromosomal duplication
• Duplications increase the amount of DNA of a chromosome compared to the normal chromosome.
• Having extra DNA in a chromosome may alter the number of genes and thus alter the amount of gene product.
• Example: • Charcot–Marie–Tooth disease
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Chromosomal duplication
Charcot–Marie–Tooth disease
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Chromosomal structural mutationsChromosomal mutations
DNA orientation in a chromosome
Chromosome structure mutations
DNA content in a chromosome
Deletion Duplication Inversion Translocation
Let’s focus on the chromosomal mutations that are associated with DNA orientation
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Chromosomal inversion
• Inversions involve the breakage of a segment and reversed and reattached.
• This mutation changes the arrangement of genes.
• Example:
• There are some known inversions in the human genome but without an affect.
• Why?
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Chromosomal translocation
• Portions of one chromosome gets relocated to another chromosome.
• There are many types of this chromosomal mutations.
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Chromosomal translocation
• Example:
• XX male syndrome!
• Translocation of SRY gene from Y chromosome to X chromosome.
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Chromosomal translocation
XX male syndrome!
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Chromosomal mutationsChromosomal mutations
Chromosome number mutations
Chromosome structure mutations
• Chromosome structure mutations: mutations that changes the amount of DNA in a chromosome or the orientation of the DNA within a chromosome.
• Chromosome number mutation: mutations that changes the number of chromosomes in a cell.
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Chromosomal number mutations
• Entire loss or gain of chromosomes due to lack of proper segregation of chromosomes during meiosis.
• This results in some gametes containing abnormal number of chromosomes.
How do chromosome separate?
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Chromosomal number mutationsChromosomes segregate due to multiple factors. Failure in any one of these factors may result in
abnormal number of chromosomes.
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Chromosomal number mutations
• What is the proper normal number of chromosomes in a somatic human cell?
• What is the normal number of chromosomes in a gametic human cell?
• Somatic cells are called ……, and gametic cells are called …..
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Chromosomal number mutations
• Euploid cell: is a cell that contains one complete set of chromosomes of exact multiples of complete sets.
• Aneuploid cell: is a cell that has a chromosome number that is not an exact multiple sets of the haploid set of chromosomes.
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Chromosomal number mutations
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Chromosomal number mutationsTypes of aneuploidy
1.Nullisomy: loss of a chromosome pair (2 chromosomes).
What do you think will happen?
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Chromosomal number mutationsTypes of aneuploidy
2.Monosomy: loss of a single chromosome.
Turner syndrome
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Chromosomal number mutationsTypes of aneuploidy
3.Trisomy: an extra chromosome.
Down syndrome
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Chromosomal number mutationsTypes of aneuploidy
4.Tetrasomy: two extra chromosomes.
Tertrasomy X (XXXX)
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To know
Chromosomal mutation
Segmental mutation
Chromosome structure mutations
Chromosome number mutation
Chromosomal deletion
Chromosomal duplicationChromosomal inversion
Chromosomal translocation
EuploidAneuploid
Nullisomy
Monosomy
Trisomy
Tetrasomy
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Expectations
• You know the different types of chromosomal mutations.
• You know chromosomal mutations that affect the DNA content and orientation.
• You know the consequences of chromosomal mutations.
• Can we repair chromosomal mutations?