chromosome biology Flashcards
what direction does DNA polymerase work in
5’ to 3’
what is the function of telomerase
protects the ends of the chromosome
what strand is the strand that has okazaki fragments
lagging strand
what are the phases of mitosis
G1, S (replication), G2, M (mitotic phase)
whats prophase
Chromosomes condense
Nuclear membrane disappears
Spindle fibres form from the centriole
whats metaphase
Chromosomes aligned at the equator of the cell
Attached by fibre to each centriole
Maximum condensation of chromosome
whats anaphase
Sister chromatids separate at centromere
Separate longitudinally
Move to opposite ends of cell
whats telophase
New nuclear membranes form
Each cell contains 46 chromosomes (diploid)
whats cytokinesis
Cytoplasm separates
Two new daughter cells
what is the purpose of centromeres
joins sister chromatids
site of kinetochore
whats interphase
genes are transcibed and dna replication occurs
whats the difference between heterochromatin and euchromatin
heterochromatin - condensed structure and silenced genes whereas euchromatin - open structure and actiive genes
what is the extragenic region?
DNA space between two genes of a genome
how is chromatin formed
dna packaged with histone proteins
what is the charge of histones?
positive
what are chromatins packaged into?
nucleosomes
what probe is useful for chromosome number?
centromeric probes
what probe is useful for detecting subtelomeric rearrangements
telomeric probes
whats the difference between meiosis and mitosis
meiosis is cell division in germ cells, diploid cells divide to form haploid (2 divides)
recombined copies as they mix
whats Oogenesis
process of egg formation
what is Spermatogenesis
process of sperm formation
which sexual gametes has more divisions
males
how many spermatids are produced per miosis
4
what are the three types of chromosomal abnormalities
numerical, structural, mutational
what is trisomy 21 and what is it caused by
down syndrome
non dysjunction
what is the incident rate of trisomy 21
1 in 650 to 1 in 700
what is trisomy 13?
paatau syndrome
whats the incidence rate of trisomy 13
1 in 5000
whats the cause of trisomy 13
non- dysjunction and unbalanced translocatoin
what is triomy 18
edwards syndrome
whats the incidence of trisome 18
1 in 3000
whats the cause of trisomy 18
non-dysjunction
what is 45,X?
what is its incidence
what are symptoms
turner syndrome and 1 in 5000 to 1 in 10000
females of short stature and infertile, neck webbing and widely spaced nipples
what is 45,XXY and what is its incidence rate
klinefelter syndrome, 1 in 1000
tall stature, long limbs, male but infertile, small testes
what is gynaecomastia
abnormal development of breast tissue in males
what are the two types of translocations
Reciprocal: involving breaks in two chromosomes with formation of two new derivative chromosomes
Robertsonian: fusion of two acrocentric chromosomes
what are the 4 structural abnormalities
translocation, deltiens, insertions and inversions
whats the differemce between germline and somatic mutations
Somatic mutations – occur in a single body cell and cannot be inherited
Germline mutations – occur in gametes and can be passed onto offspring
what are the 4 types of coding mutation
silent, missesnse, nonesense, frameshift
what do we need for polymerase chain reaction
sequence information, oligonucleotide primers, DNA, nucleotides, DNA polymerase
what are the three steps to PCR
dentaure, anneal, extend
what temperature does annealing happen
50-70
what are the advantages of gel elcetropheresis
speed, ease of use, sensitive, robust
what are the advantages of ARMS (amplification refractory mutation system)
cheap
labelling not required
electrophoresis required
primer design critical
what are the disadvantages of ARMS
needs sequence information
limited amplification size
limited amounts of product
infidelity of DNA replication
whats the function of restriction endonuclease
protective mechanism, degrades dna of invading viruses
what is restriction endonuclease?
enzymes from bacterial cells
whats the advantages of restriction digest assay
simple, cheap, no radioactive, requires gel electrophereis, not always feasible
what are the advantages/ limitations of DNA sequencing
gold standard for mutation detecting, automation and high throughput
expensive equipment
poor quality sequence read
what would alter your choice of method
direct test quick and easy cheap sensitivity specificity
