Laba Flashcards
Cytogenetics
Nucleoprotein
Cellular events involving chromosomes with genetics
DNA+ histones
Staged of DNA coiling
Nucleosome
Solenoid
Filament
Chromosome
Hetero vs eu
Tight, silenced or repetitive DNA
Relaxed and active genes
First step in gene activation
Chromosomes morphology
Freeing DNA from histones
Length/ centromere) knobs/ satellites
8 parts of a chromosome
Centromere / kinetochore(spindles attach)
Chromatid (2 sisters)
Chromatin(DNA+proteins)
2ndry constriction for nucleolar org
Telomere
Chromomeres(bead like structures that carry genes)
Matrix (non genetic material)
Chromosome membrane is
Pellicle
Plant stress is
External factor that has disadvantageous effect on the plant
Stress effects
Ex to ratio matters
Positive, eustress
Negative, distress
Water deficiency = hardening which is positive, as long as below wilting which negative
All stress types
Factors
Effect
Time
Where
Biotic and abiotic (physical can be measured)
Positive eustress and negative distress
Short term and long term
Internal and external
Biotic stress
Partial or significant damage
Microorganisms cause disease
Insects and animals cause physical damage through perdition
Plants phyto-parasitism and competition
Tolerance in plants
Adaptation, genetic and inherited to increase function and fitness in stressful environment
Acclimation, non heritable physiological modification due to stress
Mitosis studied in….which has…and ..
Meristem
Region of elongation
Region of maturation
Needed solutions
Carnoys buffer for killing and fixation (6 alcohol: 3 chloroform: 1 glacial acetic acid)
Aceto carmine stain
1M HCl for hydrolysis (10 ml abs: 90 ml water)
How to prepare aceto carmine stain
1 gm carmine in 200 ml acetic acid 45% reflux for 20 mins by gentle boiling then filter
Steps for onion roots, normal
Grow, cut 1-2 cm, carnoy, 70% ethanol, store at 4°C
Wash by water
HCl and water bath for 10 mins
Wash
Root on slidr
Treatment at 4°C
Transfer healthy bulbs to refrigerator at 4° C for 24h
And repeat the rest
Effect at 4° C
Sticky chromosomes which increases the chance for rearrangements events.
Cooling affects histones so they form sticky shapes.
Seen in metaphase and anaphase.
What is karyotyping
Procedure to study the whole set of chromosomes of an organism mainly at metaphase as they are the shortest and thickest in that phase
Onion roots at 0.5° C
Sticky and condensed in one part of the cell due to breakage and denaturation causing the regions to stick together and not undergo mitosis
Cytogenetics include
Routine analysis of G banded chromosomes and cytogenetic banding techniques and molecular cytogenetics FISH and comparative genomic hybridization.
Karyotype vs idiogram vs karyogram
Photograph of all chromosomes arranged as homologous pairs acc to size
Diagram of chromosome pairs
Diagram showing location of genes as bands
Onion 2n is
16 chromsomes
.
After many cell divisions the telomeres
shorten which causes cellular senescence
and many age-related diseases when functional
genes near telomeres are lost.
How cooling affects stickness
Telomeres have sheltrin proteins that protect them, low temp alter the shape of sheltrin causing telomeres to be naked. This causes instability and loss of cellular viability as chromosomes stick to each other.
Cooling does also affect the units of micro tubulin that forms the spindle fibers so chromosomes are unable to separate at poles so they stick and condense.
Telomeres and their function
Repetitive DNA at the end of the chromsomes.
Cap for chromosomes to prevent sticking.
Protect from degradation.
Help distinguish between normal. chromosomes and fragments.
Related to cell’s age.
Carnoys buffer use
Cell fixation to prevent futher changes
Cell permeabilization by ethanol for stain
Chromosomal spreading to visualise them
Preservation of cell, maitin integrity
Aceto carmine use
HCl use
Non specific nuclear stain that binds with chromosomes and form deep red.
Hydrolyze cell wall for visualisation
Colchicine….the chromosome and prevents…..resulting in….chromosome
This is with conc…for…hours
Shortens
Spindle formation
Spread out
0.04%
4
How colchicine inhibits mitosis
Spindle disruption
Chromosome condensation
Metaphase delay
Cell cycle arrest
Mechanism of colchicine in details
It interferes with polymerization of spindle by integrating into a- tubulin and b- tubulin dimer inducing GTP hydrolysis by GTPase turning the b subunit into an E site.
This prolongs the metaphase and nearly inhibits anaphase stimulating duplication and polyploidy.
When to use colchicine
For gout attacks it eases pain by inhibiting neutrophiles by binding to spindle preventing gout flare and having an anti inflammatory effect.
Agriculture as it induces polyploidy so better root system and nutrient uptake so increased yield and cost effective.
Details abt gout
Why
Symptoms
Why gout flare
Increased uric acid levels
Pain,swelling,joint stiffness, big toe affected
Macrophages phagocyting monosodium urate crystals
Effect of colchicine
Distorted and abnormal growth patterns for root tips with increased thickness
Sticky metaphase
Chromosomal fragmentation
Larger chromosomes
Chromosomal bridges and rings
Role of meiosis
Haploid gametes for sexual reproduction
Prevent chromosome doubling and polyploidy
Genetic variation by crossing over
Evolutionary adaptation, disease tolerance
Breeding and crop improvement enhance traits from genes from wild relatives
Meiosis phases
Leptotene
Zygote
Pachetene
Diplotene
Diakinesis
Microspore is
Microsporangium
Mother cell of pollen
Male in plants
Bread wheat is…
With …. Chromosome
Organised as
Each set represents a recombination from…..each contribute to 2 sets
This causes
Hexaploid
42
A genome, B genome, D genome
The 3 subgenomes
Variability and adaptibility
Effects of irradiation
Chromosome aberrations, disrupting notmal pairing
Meiotic abnormalities, no synaptonemal complex so increased reaarangements and breakage
Mutations to genes controlling meiotic homologous pairing
Variation, appearance of new traits
Ploidy, unbalanced gametes
Why does irradiation have various effects on meiosis
Ability to induce genetic mutations
Chromosomal abberations
Cell..and..
Breakage so structural changes
Rearrangements by deletion, duplication, translocation
Death and reproductive sterility due to radiation
Ionizibg radiation DNA damage
X-ray / gamma rays
DNA lesions
Single and double stranded breaks
Irradiation on mitosis
Sticky
Fragments
Ring
Bridge
Why study populations
Evolution, how freq of an allele that controls a trait changed with time
Factors that lead to allele freq change, many loci
How gene freq affects evolution through phenotype
Micro evolution
Natural selection
Population genetics
Allele freq
Gene pool
Change in gene freq in short time period
Well suited survives
Study allele freq in populations and how they change
How common an allele is (allele no./total alleles no.)
All copies of all genes in a population
Allele freq
Genotype fre
Phenotype freq
Allele/total alleles
Genotype/ total genotypes
No. Of white/ all
Hardy weinberg principle
In large random mating population both allele and genotype freq remain constant from generation to another unless impacted by an external factor
The formulas
P+q= 1
P2+2pq+q2= 1
P is dominant
Q is reccessive
P2 is homozygous dominant
Q2 is homozygous reccessive
2pq is heterozygous
Assumptions for hardy weinberg population
No mutation
Random mating
No gene flow
Very large population size
No natural selection
Chromosomal abnormalities
Deletion
Duplication
Inversion (paracentric , centromere not involved, pericentric)
Translocation (reciprocal and robertsonian)
Ring formation
Robertsonian vs reciprocal
Robertsonian is 2 acrocentric chromosome fusing leading to change from 46 to 45
Reciprocal is segment transfer but no change in number
Synaptonemal complex
Multiprotein complex that mediates synapsis and recombination bet homologous chromosomes
