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31 Cards in this Set
- Front
- Back
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what is the characteristic shape of chromosomes? |
short p arm, long q arm, position of centromere and G banding pattern |
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What does G banding represent? |
base composition, chromatin conformation, density of genes and repetitive sequences |
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What is the karotype? |
the number, size and shape of the chromosomes of an individual |
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What are the different classifications of chromosomes? |
Telocentric= centromere at top Acrocentric= centromere near top of chromosome Metocentric= centromere in middle of chromosome Submetacentric= centromere at 20-40% of chromosome length |
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what is the telomere? |
specialised repeated DNA sequences which protect the ends of chromosomes |
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What is rDNA? |
DNA encoding ribosomal RNA |
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What does it mean if a gene map position is 9q.34.1? |
Gene is sub band 1 of band 4 in region 3 in the long arm of chromosome 9 |
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What is polyploidy? |
When there are multiple sets of chromosomes |
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What is triploidy in humans and what does it cause? |
3n 15-20% spontaneous abortions 1 in 10000 live births, die within 1 month |
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What is tetraploidy and what does it cause |
4n 5% of spontaneous abortions very rare live births |
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What is aneuploidy? |
the condition of having an abnormal number of chromosomes caused by non disjunction |
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What is non disjunction? |
faliure of homologous chromosomes to separate at anaphase |
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What is nullisomy? |
2n-2 loss of one homologous pair of chromosomes no human examples |
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What is monosomy? |
2n-1 loss of a single chromosome one viable human example= turners syndrome |
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What is trisomy? |
2n+1 one extra chromosome lots of human examples |
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What happens in Klinefelter's syndrome? |
47 chrosomsomes = XXX (mostly) Will always be male infertile, low IQ, tall, underdeveloped testes, 50% some breast development |
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What is Turners Syndrome |
45,X (XO) Female Few noticeable defects until puberty where there is no development of secondary sexual characteristics mainly infertile |
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What are the three autosomal trisomies that can survive birth? |
Down's Syndrome Patal's Syndrome Edwards Syndrome |
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What is Downs Syndrome? |
trisomy chromosome 21 many developmental abnormalities and low IQ only autosomal trisomy to survive to adulthood |
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What is Patals syndrome? |
trisomy chromosome 13 |
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What is Edwards syndrome? |
trisomy chromosome 18 |
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Why is trisomy 21 the only one to survive to adulthood? |
it is the smallest chromosome so there are less genes on it |
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why are numerical sex chromosome abnormalities better tolerated than numerical autosomal? |
Few genes on Y chromosome and all but one X gene is inactivated (If this gene affected causes disease) |
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What can structural chromosome abnormalities be induced by? |
radiation viruses chemicals transposable elements errors in crossing over |
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What happens in chromosome deletions? |
Can be at ends of internal Deletions at ends loose telomers so chromosome is unstable and viable but if both ends are broken the chromosome forms a ring and can pass through cell division |
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What is cri-du-chat syndrome? |
Part of short arm of one copy of a chromosome 5 is deleted Causes mental retardation and physical abnormalities cat like cry |
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What are the different types of inversions? |
pericentric= includes centromere paracentric= one chromosome arm |
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What is a translocation? |
a change in the position of a chromosome segment |
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What are the types of inter-chromosomal trans-locations? |
reciprocal where the same piece is changed and non-reciprocal |
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what is the other type of translocations? |
intrachromosomal |
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What is synteny? |
the conservation of gene order in different species |
