Lecture 2: incomplete Flashcards
what order is a DNA sequence written?
5’ –> 3’
what direction is DNA and RNA synthesised?
5’ –> 3’
what is the sense strand in a gene?
The strand which ends up in the mRNA
parent strand
strand of double helix which is used as a template to create the daughter strand during replication
daughter strand
replicated strand of DNA from parent strand of double helix
Okazaki fragments
short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication. formed on the 5’ –> 3’
Centromere
the region of a chromosome to which the micro-tubules of the spindle attach
Telomere
a region of repetitive nucleotide sequences at each end of a chromosome. Determines number of replication a cell undergo.
what is the short arm of a chromosome also known as?
P
what is the long arm of a chromosome also known as?
Q
what is the telomeric sequence?
TTAGGG
what is a normal human Karyotype?
46 chromosomes, inc. X and Y
what is the structure of a telomere at the beginning of a chromosome?
initially double stranded but has a single stranded tail which loops around into a special structure.
what enzyme replicates telomeres during development?
Telomerase
where is telomerase inactive?
somatic cells
what happens to telomeres with somatic cell division?
shorten, result in finite number of cell division to senescence.
when is telomerase active?
short period during development.
what is the activity of Telomerase like in cancer cells?
Telomerase reactivation allowing cancer cells to continue dividing.
what is G-banding?
stained patterns on chromosomes. different for each chromosome.
what are chromosome coordinates?
references to genes on a chromosome. universal/standard reference
why are chromosome coordinates read from top to bottom?
chromosomes are linear
what is dipoidy?
the state of having 2 sets of genes/chromosome
what does diploidy occur?
maternal and paternal sets
why is dosage of genes/chromosome important?
For many genes, 2 copies must be present for it to function adequately. For chromosomes, 2 copies must be present.
what happens when there is an error in dosage of gene/chromosome?
haplo-insufficiency
what is haplo-insufficiency?
a copy of a gene is lost = individual is haploid for that gene. this results in pathological insufficiency
what chromosome is an exception of the diploidy rule?
X chromosome
define pseudoautosomal
a region shared by the X + Y chromosomes consisting of similar genes.
define Heterochromatin
repetitive DNA on Y chromosome which stains differently and mostly does not contain functional genes.
what region on the Y chromosome is has a vital/specific function ?
SRY in the non-heterochromatin part of the Y chromosome
what does the SRY gene do?
specify the formation of the Testis for development of male characteristics.
why does the Y chromosome lead to a male fetus?
the SRY gene on the Y chromosome. this does not depend on the number of X or Y chromosomes.
