BIOLOGY 2C03- week 7 flashcards
why is the molecular organization of chromosomes essential?
- essential for normal function and distribution f chromosomes in cell division
- plays a pivotal role in the regulation of gene expression that typifies all kinds of eukaryotic cells
Does every organism have the safe chromosome number and shape?
No, chromosome number and shape vary by organism but closely related species tend to have similar chromosome numbers
when are chromosomes dynamically active?
cells are dynamically active during interphase and move, twist and turn during transcription and dna replication
when can chromosomes be individually visualized and identified through molecular microscopic techniques?
visualized in mid-prophase through metaphase
what is a karyotype
an organized image of the chromosomes from a nucleus
what are the chromosomes in karyotypes stained with?
special compounds called flurophores
what is FISH? and what does it do?
fish; fluorescent in situ hybridization uses flurophore labels to identify chromosomes/chromosome segment OR we can use gene specific flurophores to locate individual genes
how does chromosome banding work?
- cell cycle stopped in metaphase
- cells are then dropped onto a microscope slide
- this bursts cells and ruptures the nuclear membrane causing chromosomes to spill out (chromosome spread)
- geimsa staining
What is Gemma staining and what is the difference between positive and negative g bands?
used to determine which genes are rich/prominent
positive g band: AT rich, dark and hyrophobic
negative g band: GC rich, light and less hydrophobic
chromosome arms: what do we call a short arm vs a long arm
a short arm is also called a p-arm and a long arm is called a q-arm
what are the 4 different types of chromosome shapes?
- metacentric
- submetacentric
- acrocentric
- telocentric
what is this gene’s cytogenetic location:17q12
17: the chromosome number
q: the arm (long arm)
12: the gene position distance from the centromere
What happens after chromosome breakage and what does it lead to
- when a chromosome breaks, both ends are severed at the breaking point
- the dna strands can retain their structure and attach to one another, other truncated chromosomes or the ends of intact chromosomes
- chromosome breakage can lead to partial chromosome deletion by losing a portion of a chromosome
What is terminal deletion
- a chromosome that breaks a part of its arm or the whole arm
- if the left over fragment has no centromere (acentric), it is lost during cell division
Why is an eccentric chromosome lost or not viable?
without a centromere, the eccentric fragment lacks a kinetochore. therefore, it is able to attach spindle fibres and cannot migrate to a pole of the cell during division
What are partial deletion heterozygotes?
An example of terminal deletion (chromosome losing part of arm or whole arm): chromosomes where there is one wild-type chromosome and the other is a homolog with a terminal deletion
Provide an example of terminal deletion in chromosomes.
human condition called cry-du-chat syndrome, deletion is 5p15.2-5p15.3
known for distinctive cat-cry sound emitted by infants with the condition
What is interstitial deletion
it is the loss if an internal segment os a chromosome that results from two chromosome breaks followed by a joining of the ends from either side of the lost segment (broken pieces fuse together)
What are examples of interstitial deletion
WAGR
W: wilms tumour (gene WT1)–> genitourinary development
A: aniridia (gene PAX6)—> eye development
G: genitourinary abnormalities (WT1)
R: range of development delays (BDNF)–> prevent neutrons from damage and destruction, anorexia, bulimia, memory impairment, and OCD
What happens due to unequal crossover of alleles during reciprocal recombination
unequal crossover: partial deletion, partial duplication of a chromosome
what happens if a broken chromosome attaches to the same chromosome in the wrong orientation?
chromosome inversion (180 degree reorientation of the segment)
What happens when the chromosome attaches to a nonhomogolous chromosome?
chromosome translocation
what are the 2 different types of inversion?
paracentric inversion (breakage does not include centromere) and pericentric (breakage includes centromere)
What is the consequence of crossover in the inversion loop in paracentric inversion
after crossover, we have a dicentric chromosome (chromosome with 2 centromeres) and acentric chromosome (chromosome with 1 centromere). once separated, there is a loss of chromosome segment (the acentric one), and we are left with 2 unviable segments (deletion products), 1 normal chromosome (viable) and one inversion chromosome (viable)
