Final Study Guide Deck Flashcards
What are 2 strands of DNA held together by
Hydrogen bonds
How many hydrogen bonds are between G and C
3
How many hydrogen bonds between A and T
2 ( that’s why there is a TATA box at the beginning of Transcription- break apart the A-T double bond bc its weaker than G-C triple bond)
Nucleoside vs Nucleotide
Nucleoside: Sugar and base
Nucleotide: Sugar, Base, Phosphate group
What are the purines and what are the pyrimidines
Purines: A/G (double ringed)
Pyrimidines: C and T, U (single ringed)
What are 3 structural features of DNA
- Right handed double helix, antiparallel, complementary
Which enzyme seperates the 2 strands of DNA during replication
Helicase
Which enzyme makes the RNA primer
Primase
Difference between DNA polymerase 1 and DNA polymerase 3
1: Removes DNA primers
3: Adds DNA bases 5’–>3’
What are telomeres
At the end of the chromosomes, prevent gene loss ( In somatic cells, the telomeres shorten whith every dvision. In Stem/Cancer cells, telomerase ensures that telomeres do not shorten).
Where is the telomerase gene found
In stem cells and gametes
What is a clinical application with telomerase
Premature aging occurs when there is no telomerase.
Telomerase is expressed in 90% of cancers, stimulates cell division.
What is Mismatch repair, and which cancer is related to it?
Mismatch repair: One nucleotide is removed by an exonuclease and strand is repaired
Colorectal cancer (lynch syndrome) loss of function in DNA mismatch repair
What is nucleotide excision repair and its clinical application
- Remove bulkey DNA lesions (caused by UV light, i.e. skin cancer)
- Xeroderma Pigmentosum is a defect in nucleotide excision, skin cells can’t fix themselves, so early and frequent skin cancers
Base excision repair
One or a few bases damaged, corrected easily
Double strand break repair and clinical correlation
- Most dangerous- A number of bases are damaged and there is non-homologous end joining, not accurate, and DNA lost in process.
- BRCA 1 associated (Breast Cancer)
rRNA function
site of translation, structural and functional components of ribosome
tRNA function
transfers amino acid for protein synthesis
Common structure of tRNA
cloverleaf
mRNA function
template for protein synthesis, carries genetic information from DNA to ribosome
What do eukaryotes have in their mRNA that differs from prokaryotes?
Poly- A tai and Cap
Enhancer vs silencer at promotor
Enhancer: bound by enhancer-binding transcription factor
Increase the rate of txn
Silencer: Decrease the rate of txn
3 steps of transcription in Eukaryotes
Initiation, Elongation, Termination
Transcription difference between bacteria and Eukaryotes:
SImilar
Steps: initiation, elongation and termination
Differences:
Euk have 3 different polymerase and bacteria have one
Euk DNA is complexed with proteins
Where does splicing occur
in the nucleus ( Introns taken out, exons left in and EXPRESS)
Beta Thalassemia is a condition where there is an error in which protein?
Splisosome, there is inproper splicing of the genes.
4 steps of protein synthesis
tRNA charging
Initiation
Elongation
Termination
Difference between Silent, missense, and nonsense mutations
Silent
Changed base results in the same amino acid
Missense
Changed base codes for a different amino acid
Nonsense
Changed base becomes a stop codon
Describe tRNA charging
Amino acid is transfered to RNA
Where does mRNA bind during initiation in prokaryotes?
mRNA binds to small subunit at Shine Dalgarno sequence
3 ribosome sites in elongation
A - aminoacyl
P- peptidyl
E - exit
Negative control vs positive control in operons
Negative control:
Regulatory protein is a repressor
Positive control
Regulatory protein is an activator
Inducible vs repressible control of an operon
Inducible
Transcriptional is usually off
Repressible
Transcription is usually on
What is a negative inducible
Negative control
Regulator protein is a repressor
Inducible
Txn is normally off
Something must happen to turn it in
What type of control is the LAC operon
Negative control- regulator protein is a repressor (Transcription is normally off, but if glucose is absent AND lactose is present, it is on)
Which 3 proteins does the Lac operon induce transcription of when it is on
A, Y, Z
Do eukaryotes have operons?
no, not usually. Mostly bacteria.
What are heavily methylated regions associated with
repression of transcription
Describe restriction endonuclease and its pattern
often in a palindrome, binds and cleaves DNA at restriction sites
What do you find with FISH staining
See parts of chromosomes to find abnormalities, use flourescent staining
PCR steps
Denaturing
Heat up DNA to 95 degrees Celsius
Separate dsDNA into single strands
Annealing
Cool the solution to 50 degrees Celsius
Primers anneal to complementary sequences of ssDNA
Extension
Warmed to 72 degrees Celsius
DNA polymerase is active and synthesis strands on 3’OH primer
What does Northern Blot examine
mRNA (measures expression)
What does ELISA examine
antibodies in the blood
Which pattern of inheritance only appears in males
Y-linked
Which pattern of inheritance has emales passing onto their offspring, but not males?
Mitochondirial
Describe the significance of the P53 gene
Tumor suppressor gene, triggers cell-cycle arrest. Most common genetic change in cancer
What is the proto-oncogene and what is the common mutation for cancer?
This gene is responsible for making the cell divide.
If defective, the cell will divide continuously, causing cancer.
What are oncogenes
mutated version of proto-oncogene, causes cells to grow out of control. Gain of function mutation.
RET/MET are examples.
Describe the 4 types of aneuploidy
Nullisomy
Loss of both membranes of chromosome pair
2n-2
Monosomy
Loss of a single chromosome
2n-1
Trisomy
Gains of a single chromosome
2n+1
Tetrasomy
Gains of two homologous chromosomes
2n+2
What chromosome is linked to Down Syndrome
Trisomy on chromosome 21
Which disorder commonly accompanies a robertsonian translocation
Down’s syndrome- extra part of chromosome 21 is attached to another chromosome
Describe Edward’s Syndrome dysfunction
Extra chromosome 18 ( not viable pregnancy, die soon after birth. Often born with intestines external to body).
Describe Patau syndrome
Extra chromosome 13, average survival of 10 days (not viable).
What is the chromosomal abnormality in Klienfelter syndrome
Male with an extra X chromosome (usually sterile, hypogonadism, tall)
What is the chromosomal abnormality in Poly X syndrome
3 or more X chromosomes in women
Usually benign condition, increases in severity (decreased intelligance with more X’s).
Increased risk of spontaneous abortions
What is the chromosomal abnormality in XYY males
Extra Y chromosome, possible learning disabilities.
What is the chromosomal abnormality in Turner’s syndrome
XO chromosomes (webbed neck common, broad chest, short stature, hypogondaism).
How many Barr bodies in XXYY
1
How many Barr bodies in XXXXX
4
Angelman vs Prader-Willi syndrome
Angelman: Maternal inheritance is lost on ch 15, inappropriate laughter, developmental delay, neurological symptoms.
Prader-Willi: Paternal Inhritance is lost on ch 15, mental handicap, anorexia early in life, obesity later in life.
Diseases with genetic anticipation
Huntington’s disease, Fragile X syndrome, Friedrich ataxia
What is the inheritance pattern of cystic fibrosis
Autosomal recessive
What is the pathology in Sickle Cell disease
Point mutation, leads to sickled RBC shape, hypoxia.
What is the pathology in Tay-Sach’s disease
Mutation on HEXA gene on Chromosome 15
Premature neuron death, progressive degeneration of neurons.
Death between 3-4 years in infantile onset, death between 5-15 in juvanile onset.
What type of mutation is found in the BRCA 1 gene
DNA damage repair gene (Double strand breaks) not functioning.
Activation of P53.
