Biochemistry, Chromosomes and Chromosome Diseases
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- 141) Chromatid is the name of either the left or right half of a chromosome in which stage of division?
- Metaphase.
- 142) In replication, one strand can act as a template all the way to the end, the other has to utilize a RNA prime, which is thereafter degraded, what would occur?
- Loss of DNA sequence
- 143) What would be the solution to the above problem?
- Telomeres
- 144) What are telomeres?
- A telomere is a region of highly repetitive DNA at the end of a chromosome similar to the plastic tips or “Aglets†on the end of a shoe lace. Telomeres function as an anglet. Every time linear eukaryotic chromosomes are replicated, the DNA polymerase complex stops several hundred bases before the end; if it were not for telomeres, this would quickly result in the loss of useful genetic information.
- 145) Chromosome looked in a microscope must be from a cell undergoing ______and arrested in the _________ phase?
- Mitosis, metaphase (highly condensed).
- 146) In karyotyping the chromosomes are ordered according to 2 factors?
- Size, position of centromere.
- 147) What are chromosomes with the centromere right in the middle called?
- Metacentric.
- 148) What are chromosomes with the centromere above the middle called?
- Submeta centric.
- 149) What are chromosomes with the centromere right a the top called?
- Acrocentric.
- 150) Dark G-bands in chromosomes have more or less transcriptional active genes?
- Are they more or less condensed chromatin structure? Are they higher in A-T bases or C-G bases? Less transcriptional active genes, more condensed, higher in A-T bp.
- 151) What is an Isochromosome formation?
- A chromosome with two identical arms (splits up and down, rather than left and right side).
- 152) What happens to any chromosome that looses the telomeres at both ends?
- It becomes a ring.
- 153) What type of problem do you get?
- Instability in cell division.
- 154) What is Prader-Willi Syndrome?
- A genetic disorder in which a few genes on chromosome 15 are missing or unexpressed (chromosome 15 partial deletion). Morbid obesity and some mental retardation.
- 155) What is polyploidy?
- 3 or 4 copies of all chromosomes.
- 156) What is trisomy?
- Excess of one chromosome.
- 157) What types of trisomy are compatible with life?
- 13, 18, 21 or X,Y.
- 158) What is monosomy?
- Lack of one chromosome.
- 159) What is the only monosomy compatible with life?
- Monosomy X (turner syndrome).
- 160) Trisomy and monosomy occurs at what percent in Meiosis I and Meiosis II?
- 75% and 25% respectively.
- 161) Non-disjunction leads to?
- Monosomy and trisomy.
- 162) What is Down Syndrome?
- Trisomy 21.
- 163) What percentage of Down Syndrome patients have classical trisomy 21? Mosaicism? Translocation?
- 95%, 1%, 4% respectively
- 164) What is the incident ratio for Down syndrome?
- 1:700
- 165) What is the percentage of Down syndrome fetuses spontaneously aborted?
- 80%
- 166) How many acrocentric chromosomes human chromosome pairs do we have, and which ones are they?
- 5 total) 13,14,15,21 and 22
- 167) What is a Robertsonian translocation?
- A Robertsonian translocation results when the long arms of two acrocentric chromosomes fuse at the centromere and the two short arms are lost and fuse elsewhere.
- 168) How many types of Robertsonian translocation for Down syndrome can you have?
- ? [3] Robertsonian 14-21 translocation carrier (balanced), and 14-21 translocation patient (not bablanced), and also Robertsonian 21-21 patient (not balanced).
- 169) What condition is represented by 47XX or XY, +18?
- Trisomy 18 or Edward’s syndrome.
- 170) What are some signs of trisomy 18?
- Rocker-bottom feet, clenched finger, low-set ears, small chin, 80% female, (maternal age effect), die within a year..
- 171) What condition is represented by 47XX or XY, +13?
- Trisomy 13 or Patau Syndrome.
- 172) What are some signs of Trisomy 13?
- Polydactyly, sloping forehead, cleft palate/lip, (maternal age effect), die within a year.
- 173) What condition is represented by 45X?
- Turner Syndrome (99% lead to spontaneous abortions).
- 174) What are some complications of Turner syndrome?
- Heart and renal defects.
- 175) Treatment for Turner Syndrome includes?
- Estrogen treatment at ~12, to induce secondary sexual characteristics.
- 176) What condition is present by 47 XXY?
- Klinefelter Syndrome.
- 177) What are some signs of Klinefelter syndrome?
- 1:1000 males, learning disabilities, long limbs, small testes, 55% experience gynecomastia (risk of breast cancer).
- 178) Causes percentages for Klinefelter syndrome?
- 56% maternal X, 44% paternal X, 15% mosaics.
- 179) What condition is present by 47, XXX or 47, XYY?
- (1:1000) In females additional barr bodies, maternal age effect, slight mental deficiency. (1:1000) In males increased height, decrease IQ.
- 180) What is Cri-du-Chat syndrome?
- 1:20 to 50K) A deletion of the short arm of chromosome 5.
- 181) What are some signs of Cri-du-Chat?
- Characteristic facies, distinct cry in babies, severely to mild retardation.
- 182) What is the Philadelphia Chromosome?
- The Philadelphia chromosome is a specific genetic, chromosomal abnormality that is associated with chronic myelogenous leukemia (CML) and involves an exchange of material between chromosomes 9 and 22.
- 183) What is Chronic Myelogenous Leukemia?
- Normally presents itself in middle age, involves overproduction of WBC, fatigue, night sweats and low grade fever, enlarged spleen and sternum tenderness. STI571 drug seems to control disease in early stages, and cause improvement in advance cases, this drug will probably replace bone marrow transplant.
- 184) What is the name of the master control on the Y-chromosome?
- SRY.
- 185) Determination of sex is?
- Chromosomal and gene driven
- 186) Presence of SRY will in most cases lead to male____; without SRY, the ______ stay _________?
- Gonad, gonad, female.
- 187) What is Mixed Gonadal Dysgenesis?
- Testis and streak ovary, rare, virilization. Mosaic 46, XY or 45, XO.
- 188) What is virilization?
- Refers to the development of changes which make a male body different from a female body. Most of the changes of virilization are produced by androgens.
- 189) What is Female Pseudo-Hermaphrodite?
- Only ovaries, but virilized phenotype, cause A) prenatal exposure to progesterone or androgen; cause B) inherited deficiency of 11 or 21 hydrolase in adrenal cortex (a.k.a. adrenogenital syndrome) 1:10K.
- 190) What is Adrenogenital Syndrome?
- The picture we saw of a baby with both penis and vagina. Early detection in critical in females, hyperplastia of adrenal cortex, severe cases has hyponatremia and hyperkalemia, treatment with cortisol (androgen conection).
- 192) What is Male Pseudo-hermaphrodites?
- 46, XY. (Type A) Externally and psychosexually female; no uterus and fallopian ducts, no Wolffian ducts, non-functional testes in abdomen. Often infertility and amenorrhea, androgen receptor defect (X-linked recessive), testes should be removed since they are prone to malignancies, a.k.a. testicular feminization. (Type B) 46, XY, partial feminization at birth, Wolffian structures present; most often virilization at puberty, Cause 5 alpha-reductase deficiency (Autosomal Recessive), no conversion of testosterone (less active) to dihydrotestosterone (more active)