WEEK 6 (Variation in chromosomes) Flashcards
What are translocations?
Rearrangements of genetic material in which a segment is inverted, exchanged with a segment of a non-homologous chromosome, or merely transferred to another chromosome
What is a Deletion?
When a chromosome breaks in one or more places and a portion of it is lost, the missing piece is called a DELETION
What are Terminal and Intercalary Deletions?
TERMINAL DELETIONS = Deletion occurs near one end of the chromosome
INTERCALARY DELETIONS = Deletion occurs within the interior of the chromosome
What is distinguishable about Progeny cells following mitosis or meiosis?
The portion of the chromosome that retains the CENTROMERE REGION is usually maintained when the cell divides, whereas the segment WITHOUT the CENTROMERE is eventually lost in PROGENY CELLS following mitosis or meiosis
What must happen for synapsis to occur between a chromosome with a large intercalary deletion and a normal homolog?
The unpaired region of the normal homolog must “buckle out” into a DELETION or COMPENSATION LOOP
Describe Cri du Chat syndrome
CAUSES: Congenital deletion on short arm of chromosome 5
SYMPTOMS:
- Microcephaly (small baby head)
- Moderate to severe intellectual disability
- High-pitched crying
- Epicanthal folds
- Cardiac abnormalities
What is Duplication?
When any part of the genetic material is present more than once in the genome
What can produce a compensation loop?
Pairing in heterozygotes
How can Duplications arise?
As the result of unequal crossing over between synapsed chromosomes during meiosis or through a replication error prior to meiosis
What are the important aspects of Duplications?
- May result in GENE REDUNDANCY
- May produce PHENOTYPIC VARIATION
- Important source of GENETIC VARIABILITY during evolution
Duplication of chromosomal segments has the potential to what?
Amplify the number of copies of individual genes
What is Gene redundancy?
The existence of multiple genes in the genome of an organism that perform the same function
What does molecular hybridisation enable us to do?
Determine the percentage of the genome that codes for specific RNA sequences
