13318639
Description
Flashcards by Sophie Byrne, updated more than 1 year ago
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Created by Sophie Byrne
about 6 years ago
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| 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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