Chap 10 Developmental Genetics and Abnormalities Flashcards
What is aneuploidy and polyploidy?
Aneuploidy is the presence of abnormal number of chromosomes in a cell
Polyploidy is the state of a cell having more than two paired sets of chromosomes.
Explain Deletion in Chromosomes
Portions of chromosome are deleted and the effects depend on the region deleted, if a non essential part of the chromosome is deleted no harmful effects will occur. eg.17q12
Explain duplication in chromosomes and give an example.
Portion of the chromosome is duplicated. e.g Potocki Lupski Syndrome 17p11.2.Infants withPotocki-Lupski syndromemay have weak muscle tone (hypotonia) and swallowing difficulties (dysphagia) that lead to feeding problems.
Babies and children withPotocki-Lupski syndromehave delayed development, including delayed speech and language skills and gross motor skills such sitting, standing, and walking.
Explain inversion in chromosomes
Aninversioninvolves the breakage of a chromosome in two places; the resulting piece of DNA is reversed and re-inserted into the chromosome.
2 Types of Inversion
Paracentric inversion is inversion that occurs along the p or q arm and does not involve centromere
Pericentric inversion is inversion that involves the centromere
Explain translocation in chromosomes
A piece of a chromosome being attached to a non homologous chromosome.
Reciprocal Translocation where two detached fragments of non homologous chromosomes are switched.
Non Reciprocal Translocation where there is a transfer of segment if DNA from one chromosome to another non homologous chromosome.
Robertsonian Translocation is fusion of the whole long arms of two acrocentric homologous chromosomes.(acrocentric means small p arm)
Explain ring chromosomes and give an example.
Ring Chromosome is where the ends of a chromosome are fused together. eg. Ring Chromosome 14 Syndrome a condition characterized by seizures and intellectual disability.
Explain Isochromosome
Isochromosome is an abnormal chromsome that has two identical arms due to duplication of one arm and loss of the other.The chromosomes break on the transverse plane.
How do chromosomal abnormalities occur?
Non disjunction during M1 OR M2 (failure of the chromosomes to seperate)
During development of sperm and egg leads to meiotic disjunction trisomy or monosomy.