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Large Scale Chromosomal Aberrations

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Year 1 BIO154 - Genetics I Flashcards on Large Scale Chromosomal Aberrations, created by Sophie Byrne on 04/17/2018.
Sophie Byrne
Flashcards by Sophie Byrne, updated more than 1 year ago
Sophie Byrne
Created by Sophie Byrne over 4 years ago
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Resource summary

Question Answer
What are the 3 types of chromosome mutations? Relocation Loss of genetic material Gain of genetic material
On chromosomes, which is the short arm and which is the long arm? Short - p arm Long - q arm
What is aneupolidy? When the chromosome number differs from normal euploid (2n) cells by part of a chromosome set
What are 3 types of aneuploidy? Monosomic (2n - 1) Trisomic (2n + 1) Nullosomic; lacking a single chromosome pair (2n - 2)
What are the 4 aneuploids of sex chromosomes? Give 2 examples of conditions that arise from aneuploidy. XXY - Klinefelter sydrome XYY XXX XO - Turner syndrome
How does aneuploidy occur? Give detail of the process. Nondisjunction (when homologous chromosomes or sister chromatids fail to separate during nuclear division --> abnormal chromosomal distrib.) - At first division: Spindle fibres from a single pole attach to centromeres of both homologour chromosomes of a pair. Frequent if no crossing over occurs - At second division: Spindle fibres from a single pole attach to centromeres of both sister chromatids Sister chromatids move to same pole Can be lethal to embryo
Give 3 examples of autosomal trisomy and where they occur Down syndrome - 3 copies of chromosome 21 (increased incidence as maternal age increases) Patau syndrome (trisomy 13) Edwards syndrome (trisomy 18)
What are the 4 types of structural variation of the chromosome? 1. Deletions 2. Duplications 3. Inversions - Pericentric inversion: on one side of centromere - Paracentric inversion - regions change places 4. Translocations - Reciprocal - swap - Nonreciprocal
WHY does structural variation of the chromosome occur? - Errors (e.g. deletions) occur when rejoining broken chromosome segments - Improper crossing over (NAHR - non-allelic homologous recombination)
Give an example for each type of structural variation: deletions and duplications Deletion: - Cri-du-chat/5p syndrome (part of short arm of chromosome 5. 1 in 50,000 births) Duplication: - Cat eye syndrome (rearrangements of chromosome 22) - Rearrangement included inverted duplication spanning p to q11.2
HOW do structural chromosome variations occur? - Spontaneous in gonads of parents with otherwise normal chromosomes - Recombination in a parent w/ heterozygous reciprocal
How do robertsonian translocations in Down's syndrome occur? What is the frequency of this? - Breakage in chromosome causes fusing b/w chromosomes 14 and 21 - Trivalent formation in meiotic pairing - 2 normal copies of chromosome 21, 1 of chrom. 14, 1 21-14 fusion - 3% of Down's syndrome cases
What is the definition of a karyotype? The number and appearance of the chromosomes
What are 2 types of variation in the human karyotype? Variation in chromosome number Variation in chromosome structure
What is the cause of age-related nondisjunction? - Human meiocytes are arrested at diplotene (P1) before birth - Chiasmata hold sister chroms. (bivalents) together and must remain intact until meiosis resumes during menstrual cycle - As time passes, chance of bivalent breakdown increases - Most nondisjunction occurs at Anaphase 1
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