Flashcards in W2 Deck (136)
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1. What are the 4 stages of mitosis, describe each.
2. conversion of 2n content of DNA into?
-Prophase (DNA has been replicated and the duplicated chromosomes are arranged as sister chromatids, attached at the centromere)
-Metaphase (the sister chromatids line up in preparation for cell division)
-Anaphase (sister chromatids separate)
-Telophase (cell division)
2n content of DNA -->4n preparation for cell division-->2 daughter cells (2n)
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Meiosis generate what type of cells?
How many divisions?
Describe the chromosome/sister chromatids in the process.
-generate haploid cells from diploid cells –
-two cell divisions are required.
-After the first division, the sister chromatids are still attached, as opposed to separated as in mitosis.
-The second cell division then separates the identical chromosomes.
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Describe Independent Assortment of Chromosomes
As chromosomes migrate to daughter cells during meiotic division, they do so independently of other chromosomes (otherwise, Mendelian genetics would not work)
independent assortment of nonhomologous chromosome during meiotic division I
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Crossing over in meiosis happens when?
What type of chromosome is involved?
The ares of crossing over is called?
How many cross overs during division and per chromosome?
What does this link to?
-prophase I of meiosis (synapsis)
-pairs of sister chromatids crossover of genetic material can occur btw chromatids
-chiasma
-30-40 (1-2)
-genetic linkage
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Definition of:
1. Metacentric
2. submetacentric
3. acrocentric
4. telomere
5. chromosome arms
1. centromere center
2. centromere non-centere
3. stalk
4. end of chromosome
p=short; q= long
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banding patterns of chromosomes
1. two types of treatments, describe
2. What allows further subdivision into what?
3. Other banding techniques? (5)
1. enzymatic tx with trypsin & stain chromosomes
- G-banding (Giemsa)-->light band=euchromatin, transcriptionally active; dark abnd= heterochromatin
3. Giemsa binds better to AT rich region-->subdivsion of regions & sub-region (14q21)
4.
Q-banding (fluorescent)
R-banding (reverse banding from Giemsa, need to heat DNA)
C-banding (highlights centromeres; remove proteins)
Spectral karyotypes (either chromosome specific, or analyze different areas of the same chromosome)
FISH – fluorescent in situ hybridization
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Chromosome & karyotype nomenclature
Meaning of & example relating to chromosome
1. 1-22
2. X, Y
3. p
4. q
5. del
7. der
8. dup
9. ins
10. inv
11. /
12. t
13. ter
14. r
15. +/-
1. autosome number
2. sex chromosomes
3. short arm of chrome, petit
4. long arm
5. deletion of chromosome material
6. derivative, structurally rearranged chrom
7. duplication of parts of chrom
8. insertion of DNA into
9. inversion of DNA within
10. indicate mosaicism (2 different cell types within one individual)
11. translocation (region moved are described after t symbol)
12. terminal (or pter, qter)
13. ring chrom
14. placed before chromo #, addiitons/deletion of whole chromo
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Explain Karyotype
1. 46, XY
2. 47, XX, +21
3. 47, XY, +21/46, XY
4. 46, XY, del(4)(p14)
5. 46, XX, dup(5p)
6. 46, XX, inv(3)(p21;q13)
7. 46, X, r(X)
1. normal male chromosome constitution
2. female with trisomy 21
3. male c mosaic of trisomy 21 cells and normal cells
4. male with deletion at chromosome 4 at short arm designated band 14
5. woman with duplication of short arm at chromosome 5
6. female with inversion on chromosome 3 between band 21 on short arm and band 13 on long arm
7. female with one normal X chromosome and one ring X chromosome
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Definition of:
1. euploid
2. diploid
3. triploidy
4. aneuploid
-monosomies
-trisomies
5. consequences of these abnormality?
1. human with multiple of 23 chromosomes
2. 46 chromosomes
3. 69 chromosomes
4. does not have a multiple of 23 chromosomes
-1 copy of a chromosome always lethal if autosomal
-a limited number allow survival
5. spontaneous abortion due to too many expressed genes in polyploidy, on autosomes, is detrimental to development
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What causes polyploidy?
Result from what during maternal meisos II?
Common forms? (3)
what are dignynic & diandric
-fertilization of same ovum by 2 or more sperm
-errors in maternal meiosis II -->egg with diploid # of chromosomes-->fertilized by a sperm with haploid # chrome.
-69, XXX+69, XXY
-digynic=46 chrom from mom
-diandric= 46 chrom from dad (65%-75%)
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What causes aneuploidy?
-prevalance
-common causes
-related to
1 in 300 newborn infants are aneuploid
- non-disjunction
-More common in eggs > sperm
-trisomies due to errors in maternal meiosis I
egg suspended in meiosis II
-maternal age
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Describe non-disjunction in meiotic & mitotic division
nondysjunction in Meosis I
-chromosome are different in the gametes
nondisjunction Meiosis II
-chromosome are identical gametes
-both lead to trisomic & monosomic zygote
mitotic -->mosaicism
-one of the cells has no disjunction event during mitosis
-will have mixture of normal and trisomic cells, monosomic usually die off
-all daughter cells with trisomy
-single cells could live with trisomy
-common in tumors
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Major Chromosomal Aneuploidy Syndromes Compatible with Live Births
-what is the chromosomal abnormality?
-clinical features?
-why does chrome 13, 18, 21 trisomies occur?
1. patau's syndrome
2. edward's syndrome
3. down syndrome
4. turner syndrome
5. klinefeltter's syndrome
6. Triple X
7. XYY
1. trisomy 13
-cleft lip & palate, several CNS anomaly, polydactyly
2. trisomy 18
-low birth wt, CNS anomalies, heart defects
3. trisomy 21
-hypotonia, characteristic facial features, developmental delays
4. monosomy X
-short stature, amenorrhea, lack secondary sexual development
5. XXY
-small testes, infertility, tall stature, learning problems
6. XXX
-learning disabilities, no major physical anomalies
7. XYY
-learning & behavior problems
13, 18, 21 are small chrom. with large sections of heterochromatin (inactive)
-21 smallest mildest symptoms
-13 & 18 lead to early death
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Structural Abnormalities in Chromosomes
describe:
1. pericentric
2. paracentric
3. duplication
4. interstitial & terminal deletions
5. which are inversion vs.insertion vs. duplication?
6. what has genetic lose and which does not?
1.
2.
3.
4.interstitial= middle; terminal= end
5. pericentric & paracentric= inversion
insertion of one part into another chrom. or duplicated from original and insert into original
6. deletion, isochromosome, microdeletion= genetic loss
7. no genetic loss= inversion, reciprocal translocation
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What is isochromosomes?
What does it lead to?
- abnormal centromere division
-result in either duplication of p arm or deletion of q arm (iso-p)
-or duplication of q arm & deletion of p arm (iso-q)
-loss of genetic material
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Compare & Contrast :
Reciprocal vs. Robertsonian translocation
Reciprocal
-No loss of genetic material
-Carrier usually phenotypically normal; problems with gametes
-The resulting chromosomes are called derivative chromosomes
Robertsonian
-occur between acrocentric (centromere close to the end) chromosomes (13, 14, 15, 21, 22).
-short arms lost, one long arm fused generated.
-genes lost from short arms are rRNA genes, which are duplicated elsewhere in the chromosome
-carriers are phenotypically normal.
-individuals will have a karyotype of 45 chromosomes.
-problems with gamete formation.
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Gametes in reciprocal vs. robertsonian translocation
-both have 1/3 for normal function
-the unbalanced monosomy & trisomy gametes not viable for live
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What is microdeletion syndromes?
what is lost?
how is it detected?
example?
-Disorders due to a small (< 5 megabases) chromosomal deletion; very complex phenotypes observed
-Multiple genes lost via the deletion-->monosomy for a number of genes
-deletions can only be detected using specific probes to the missing region (FISH)
-Angelman and Prader Willi syndromes are example (15q11)
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Indication for prenatal diagnosis include:
Methods to obtain fetal cells for cytogenetic study include
-advanced maternal age (>35)
-Previous child with a chromosomal abnormality
-Family history of chromosomal abnormalities
-Abnormal prenatal screening study
Amniocentesis
Chorionic Villus sampling
Cordocentesis
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amniocentesis
when is it perfumed?
risk of what?
how is it performed?
what is being studied?
1. Gold Standard
2. 0.5% risk of procedure-induced pregnancy loss
3. Perform at 15-16 weeks gestation
4. Amniotic fluid is obtained using ultrasound to guide the placement of the needle in the uterus
5. Remove amniotic cells, culture in lab, do cytogenetics study
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chorionic villus sampling
when is it performed?
risk?
how is it done?
1.Performed at 10-12 weeks gestation
2. Has a 0.5% risk of procedure induced pregnancy loss
3. Removed cells are from the placenta (chorion), although they are contaminated with maternal cells. 4. Ultrasound is used to guide needle placement. A separation procedure is required to remove maternal cells from the sample
5. Cells are grown in the lab and analyzed
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Cordocentesis
what is it?
when is it indicative to use?
how is it done?
at what gestation?
risk?
advantage?
1.Umbilical blood sampling; used if inconclusive results are obtained by other procedures
2. Ultrasound guides needle into the umbilical artery (obtain blood instead of amniotic fluid)
3. Performed after 18 weeks of gestation
4. Has a high rate of fetal loss: 1-2%
5. Advantage is less time is required to obtain results (blood cells grow more rapidly)
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trancriptional initiation & elongation steps (5)
1. binding of DNA pol
2. separate DNA
3. binding of 1 st nuc by base paring
4. binding of 2nd nuc & 1st: PPP remains at 5' end and PPi splits from 2nd nuc
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give a general view of a gene from 5'-->3'
-4 important structures
5'-->3'
1. regulatory sequence
2. promoter
3. start point for transcription
4. coding region of gene
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Promoters--the business end of a gene
1. activator & repressors proteins are know as? and what role does it play?
2. what are the two promoter consensus sequence?
1. transcriptional factors, bind at particular sequence with high affinity that affects transcriptional efficiency
2. TTGACA upstream near -30, TATAAT downstream near -10
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coding strand vs. template strand
1. discuss it's characteristics and complementary
2. which strand is read by RNA polymerase?
1. coding strand has the identical sequence informarion to the mRNA
-template strand is the one actually read by RNA polymerase which synthesize a complementary mRNA identical in sequence to the coding strand
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Prok promoter recognition involve what protein?
what is this protein bound to?
what transcribe all prok genes?
how many ways can pok terminate transcription?
1. alpha protein which only recognizes promoter sequence when it is bound within the holoenzyme
2. RNA pol is a multi-subunit enzyme that transcribes all pork genes
3. two ways for termination: Rho-dependent or Rho-independent
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Compare & contrast
Rho dependent vs. Independent termination of transcription
Rho-dependent
1. helicase protein called rho inds RNA-DNA duplex downstream of translation STOP signal (other signal obscure by ribosomes)
2.denatures the RNA=DNA duplex using its ATP-dependent unwinding activity
Rho-independent
1. termination does not involve other secondary proteins
2. specigic G_C rich sequence signal downstream of translation STOP signal causes RNA pol to stall out over an immediately following A/T rich sequence
-DNA duplex is re-established via annealing, expel RNA from transcription bubble
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Properties of EUK RNa polymerase
I, II, III
1. localization
2. cellular transcripts
3. effect of alpha amanitin
function of:
1. rRNA
2. miRNA
3. tRNA
4. How many RNA pol are in prok. ?
Euk:
pol I:
-nucleolus
-18S, 5.8S, 28S, rRNA
-insensitive
pol II
-nucleoplasm
- mRNA precursors, non-coding RNAs (miRNA) precursors
-strongly inhibited
pol III
-nucleoplasm
-tRNA, 5S rRNA
-inhibted by high concentration only
1. important in translation
2. ...in gene regulation
3. --- in translation
4. PROK.: all RNA species are transcibed by 1 single RNA pol.
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