Exam 4 Flashcards
(35 cards)
Which one of the following is NOT true regarding nucleotide synthesis?
a) hypoxanthine is the precursor to the purine ring
b) orotate is the precursor to the pyridamine ring
c) a dehydrate closes a ring
d) a dehydrogenate creates a single bond
d) a dehydrogenate creates a single bond…false…it creates a double bond
Which one of the following is NOT true regarding the 2 pathways for biosynthesis of nucleotides?
a) the DeNovo method makes nucleotides from scratch and is energy expensive
b) the Salvage pathway recycles free bases and is energy economical
c) The committed step of the DeNovo purine pathway (formation of 5-phosphororibosyl-1-amine) is catalyzed by glutamine-pprp amidotransferase
d) PPRP is a only a key substrate in the synthesis of purines but not with pyrimidines
d) PPRP is a only a key substrate in the synthesis of purines but not with pyrimidines…false…it is a key substrate for both
What medication inhibits the catalyzation of the committed step of the DeNovo pathway?
Azaserine or Acivicin
Match the following medications with their function:
1) Allopurinol (treats gout)
2) Novobiocin/nalidixic acid/ciprofloxacin
3) methotrexate/trimethoprim/aminopterin
4) rifamyacin (treats tuberculosis)
a) inhibits bacterial DNA gyrase and prevents supercoiling
b) inhibits dihydrofolate reductase which prevents formation of tetrahydrofolate which is important in nucleotide synthesis (a deficiency in this causes spina bifida)
c) blocks urate synthesis
d) inhibits prokaryotic RNA polymerase and blocks initiation of transcription
1) Allopurinol (treats gout)–c) blocks urate synthesis
2) Novobiocin/nalidixic acid/ciprofloxacin–a) inhibits bacterial DNA gyrase and prevents supercoiling
3) methotrexate/trimethoprim/aminopterin–b) inhibits dihydrofolate reductase which prevents formation of tetrahydrofolate which is important in nucleotide synthesis (a deficiency in this causes spina bifida)
4) rifamyacin (treats tuberculosis)–d) inhibits prokaryotic RNA polymerase and blocks initiation of transcription
All of the following inhibit translation, EXCEPT:
a) Diphtheria toxin
b) tetracyclines
c) bacitracin
d) streptomycin
e) chloramphenicol
c) bacitracin (bacitracin targets cell wall synthesis by blocking phosphatase that recycles dolichol phosphate)
Which medication inhibits thymidylate synthase, an enzyme that converts dUMP to dTMP?
a) methotrexate
b) fluorourcil
c) tetracycline
d) tunicamycin
b) fluorourcil
Which disorder is linked to a deficiency in phosphotransferase, therefore cannot hydrolyze mannose leading to severe psychomotor retardation and skeletal deformities?
a) Prader-willi syndrome
b) Angelman syndrome
c) I-cell disease
d) Tay-sachs disease
c) I-cell disease
Match the following disorders to their causes:
1) Gout
2) Lesh-Nyhan syndrome
3) Prader-willi syndrme
4) Angelman syndrome
5) Tay-sachs disease
a) complete lack of HGPRT
b) partial lack of HGPRT
c) hexoaminodase A deficiency
d) Mutant maternal chromosome 15 (deletion of 15q11-13), only paternal expressed
e) Mutant paternal chromosome 15 (deletion of 15q11-13), only maternal expressed
1) Gout–b) partial lack of HGPRT
2) Lesh-Nyhan syndrome–a) complete lack of HGPRT
3) Prader-willi syndrme–e) Mutant paternal chromosome 15 (deletion of 15q11-13), only maternal expressed
4) Angelman syndrome–d) Mutant maternal chromosome 15 (deletion of 15q11-13), only paternal expressed
5) Tay-sachs disease–c) hexoaminodase A deficiency
Match the following disorders to their causes:
1) split-hand deformity
2) SCID (boy in bubble) disease
3) Cystic fibrosis
4) phenylketonuria
5) Xeroderma pigmentosum
a) defective thymine dimer repair system, cannot protect against UV
b) Adenosine deaminase (ADA) deficiency
c) reduced penetrance genetics
d) phenylalanine hydroxylase deficiency
e) deletion mutation for 1 whole codon (triplet deletion) for PHE
1) split-hand deformity–c) reduced penetrance genetics
2) SCID (boy in bubble) disease–b) Adenosine deaminase (ADA) deficiency
3) Cystic fibrosis–e) deletion mutation for 1 whole codon (triplet deletion) for PHE
4) phenylketonuria–d) phenylalanine hydroxylase deficiency
5) Xeroderma pigmentosum–a) defective thymine dimer repair system, cannot protect against UV
All of the following disorders are autosomal recessive EXCEPT which TWO?
a) Cystic fibrosis
b) Sickle cell anemia
c) Huntington’s corea
d) Tay-Sachs
e) Lesh-nyhan syndrome
f) Xeroderma pigmentosa
g) phenyketonuria
c) Huntington’s corea—-autosomal dominant
e) Lesh-nyhan syndrome—-X-linked
Which one of the following is NOT true?
a) The ring structure components of the DeNovo pyrimidine synthesis are: glutamine, HCO3, and aspartate
b) The ring structure components of the DeNovo purine synthesis are: 2 glutamine, 1 glycine, 1 aspartate, 2 formate, and 1 CO2
c) The committed step of the DeNovo purine pathway is step 1: formation of 5-phosphororibosyl-1-amine and is catalyzed by glutamine-pprp amidotransferase
d) The committed step of the DeNovo Pyrimidine pathway is step 2: formation of N-carboylasptate and is catalyzed by aspartate transcarboylase
e) all of the above are true
e) all of the above are true
Which one of the following is NOT true?
a) Hyperactive PRPP synthetase can lead to elevated serum urate and cause gout.
b) Methotraxate is used to treat gout
c) excess PRPP accelerates purine biosynthesis
d) People with gout have a partial lack of HGPRT which reduces the salvage pathway leading to excess PRPP and accelerated purine synthesis
b) Methotraxate is used to treat gout…false…allopurinol treats gout
(T/F) Chargoffs rule states that the percentage of G’s equals the percentage of C’s and the percentage of A’s equals the percentage of T’s
true
Which one of the following is NOT true?
a) the higher the GC content of DNA, the higher the melting temperature (Tm)
b) Hyperchromism is associated with higher UV absorbance
c) DNA in a cell is maintained in a positively supercoiled state
d) Supercoiling is modified by the following 3 enzymes: topoisomerase 1, DNA gyrase, helicase
c) DNA in a cell is maintained in a positively supercoiled state…false…it is maintained in a ‘negatively” supercoiled state
Which one of the following is NOT true?
a) 2 types of extrachomosomal DNA is bacterial plasmids and eukaryotic mitochondrial DNA
b) the genome is the total amount of DNA within a cell, including extrachromosomal DNA
c) Bacterial chromosomes are always double stranded, circular, and lack telomeres
d) plasmids never carry antibiotic resistance (r-factors)
d) plasmids never carry antibiotic resistance (r-factors)…false…that is where they are
Which one of the following is NOT true?
a) Humans normally have 22 pairs of autosomes and 2 sex chromosomes
b) The Karyotype involves only the nuclear complement of an organism (excludes mitochondrial DNA)
c) 30% of our genome encodes genes, while 1.5% of our genome is exons
d) DNA + histone core=nucleosome
e) all of the above are correct
e) all of the above are correct
How do you squish 1 meter of DNA material into the nucleus of a cell?
You must compact it by supercoiling:
- 2 chromatids=10 coils each
- 1 coil=30 rosettes
- 1 rosette=6 loops
- 1 loop =75,000bp
- 1 solenoid=6 nucleosomes (30nm of fiber)
- nucleosome=beads on a string
- remove nucleosomes and you have double stranded DNA
Which one is not considered one of the 3 specialized regions required for all chromosomes?
a) telomeres
b) centromeres
c) origin of replication (ORI): attracts the DNA polymerase
d) satelite
d) satelite
What 5 chromosomes condense to form the nucleolus?
13.14.15.21.22
Describe the classifications of centromeres
The classifications describe the location of the centromere within the chromosome. metacentric=center, submetacentric=slightly off center, acrocentric=near one end (p arms would be the smallest)
Which one of the following NOT true?
a) arms of chromosomes are called p (petite) and q (long)
b) The DNA template has a template (anti-sense) strand and a non-template (sense) strand
c) the sense strand and the mRNA have the same sequence
d) downstream is 5’ end and upstream is 3’ end
d) downstream is 5’ end and upstream is 3’ end…false….its the opposite (upstream is 5’ and downstream is 3’)
Which of the following is NOT true?
a) AUG is the stop codon
b) Exons code while introns are removed
c) transcription occurs in the nucleus, while translation occurs in the cytoplasm
d) in genetics, wild type means “normal”
a) AUG is the stop codon…false….its the START codon and UAG, UGA, UAA are the 3 stop codons
Which one of the following is NOT true?
a) inactivated X chromosomes are called barr bodies
b) son’s can pass on mitochondrial disorders to their offspring only if it was passed on to them by their mom
c) the lyons hypothesis states that all females are mosaics with respect to their X chromosome
d) the 3 stages of DNA replication are initiation, elongation, and termination
b) son’s can pass on mitochondrial disorders to their offspring only if it was passed on to them by their mom…false…only females can pass to offspring (male or female) but only female offspring can pass it on
(T/F) In X-linked pedigrees, females are usually carriers because they have 2 X’s, females can pass on to males, however daughters of affected males can only be carriers
true
