Exam 2 Flashcards
What are the 4 types of Chromatin?
Euchromatin (less dense and active)
Heterochromatin (condensed and inactie)
Perinucleolar Chromatin
Intranucleolar Chromatin
Functions of the Nucleus
Command center
Reproduction
Heredity
Moment by moment functions of all cells
Define a human genome
How many kinds of genomes are there in human cells?
An organisms genome consists of the DNA that contains one complete copy of all the genetic information that it contains
Two types Mitochondrial and Nuclear
What is a gene?
Segment of DNA that determines sequence of amino acids in a protein.
DNA Location
Sugar
Bases
Form
Synthesis
Function
Nucleus and some in mito and chlroplasts
Deoxyribose
AGCT
Dbl stranded in euk nucleus, single in mito
During S phase of interphase only
Storage of genetic info
RNA Location
Sugar
Bases
Form
Synthesis
Function
Cytoplasm, 10 percent in nucleolus
Ribose
AGCU
Single stranded except folded tRNA
Continually made and broken during all interphase
Synthesis of proteins
What is a ribozyme?
Link the existence of ribozymes with origin of life
The rRNA component is also thought to perform the peptidyl transferase activity
First catalytic macromolecules were RNAs cuz could carry information AND replicate itself to replicate and transfer infer between generations
Watch Transcription, Translation, Replication videos
OKAAY
A typical protein coding gene has which three elements?
A core promoter
Proximal control elements
A transcription unit
What is the DNA promoter site?
Core promoter?
Proximal control elements?
Enhancer elements?
Specific sequence of several dozen base pairs that determines the location of RNA synthesis and which DNA strand will act as template strand. Located on left side of Start codon (3’ end)
TATA box
Further upstream from TATA box (left side of it)
Enhancer elements are further left than that (CAAT box and GC box
What is the role of Transcription factors in mRNA synthesis?
Significance of the trailer region in mRNA?
To allow RNA polymerase enzyme to attach.
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What are the two types of termination signals in transcription?
rho factor protein and a short GC rich sequence followed by several U bases near 3’ end of mRNA itself. The latter causes RNA to fold into hairpin loop
Role of introns
May protect integrity of genes in families from elimination through unequal crossing over
Act as regulatory elements in transcription of certain genes
Hasten the evolution of new and potentially useful proteins
What are spliceosomes and what are they made of?
They assemble on introns and are made up of small nuclear ribonucleoproteins (snurps) which cut out introns during mRNA processing.
What is the function of the wobble position in tRNA?
Permits flexibility in the pairing between the third base of the mRNA codon and the complementary base in the anticodon.
Inosine example (I) can pair with U, C, or A so anticodon UAI can regonize AUU, AUA, or AUC which all code for isoleucine.
Wobble permits use of fewer tRNAS for some AA than the number of codons that specify those AA
Four processes of protein synthesis
Activation: free AA in cytoplasm combine with tRNAs
Initiation: Ribosomal subuits, mRNA and met tRNA form initiation complex in cytoplasm
Elongation: (binding, transpeptidation, translocation)
Termination: Dissocation
Requirements of Activation
Inatitation?
Elongation?
Termination?
ATP, MG2+, Aminoacylsynthetase
GTP, Mg2+, Initiation factors (IF-1,2, and 3
Another aminoacyl tRNA, GTP, Mg2+ and Elongation factors (EF-Tu
Stop codon, GTP, Release factor (RF1,2 3)
Four different possible sites of regulation of protein synthesis
mRNA synthesis - inhibition blocks protein synth
tRNA and rRNA synthesis inhibition - controls rate of protein synthesis
Protein Synthesis on Ribosome - no translation
Stability of mRNA -
Define induction
Define repression
When something stimulates the synthesis of a product for its own utilization (Lactose stimulates galactosidase)
When something blocks the synthesis of reactants necessary for its own synthesis. (Histidine blocking synthesis of ten enzymes needed to make it)
Summary of Gene level repression mechanism
Repressor gene —> Repressor protein (activated when inducer is absent)
It binds with operator gene
Therefore, repressor blocks both promoter and operator genes –> RNA polymerase can’t combine with promoter gene
Preventing the synthesis of mRNA, which blocks enzyme synthesis
Summary of gene level Induction mechanism
Repressor gene –> Repressor protein synthesized
Repressor protein Inducer (lactose) is present and binds with repressor to inactivate it
Operator and promotor sites are now free
RNA polymerase combines with promoter and transcription begins
mRNA synthesis proceeds which leads to enzyme synthesis
Induction can be viewed as an inhibition of inhibitor
Are all genes in DNA subject to induction and repression?
If not how are they controlled?
NO
End-Product inhibition.
Five levels of gene regulation
Genomic Control
DNA alteration, chromatin decondensation,
histone acetylation
Transcriptional Control
Transcript factors interactions and DNA control
elements so specific genes can turn on or off.
Control of RNA Processing and Nuclear Export
RNA splicing and mRNA export regulation (pores)
Translational Control
Controll rate of mRNA synthesis and degradation
Posttranslataional control Mechanisms
Altering protein structure and function
Describe the Two periods in love of an animals cell cycle
Interphase - non division period G1 - DNA->RNA->protein->growth S - DNA-> 2 daughter DNA G2 - Cytoplasmic cell growth Go - Cells destined never to divide again
Division or Mitosis - DNA condenses to form chromosomes and cells divide
Describe the three main checkpoints in eukaryotic cell cycle.
G1 Checkpoint (restriction point) checks for cell size, nutrients, GF, DNA damage
G2 checkpoint
checks for Cell size, DNA replication
Spindle Assemp=bly checkpoint
Checks for chromosome attachment to spindle
If checkpoints are so great then why cancer happen?
Malfunctioning of growth factor signaling pathway
also caused by mutant genes called oncogenes that code for excessive amounts of growth factor signaling pathway
What are replicons and replication bubbles?
Why is it necessary to synthesize a RNA primer BEFORE DNA replication can begin?
Since linear replication occurs at multiple sites this creates replication units known as replicons
Origin of replication lies at center of each replicon. Replication occurs both opposite ways forming a replication bubble
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What is the end replication problem?
What are telomeres?
During growth of lagging strand, when reaches end of the DNA strand and the final RNA primer is removed by a 5’ to 3’ exonuclease, the final gap cannot be filled because there is no 3’ end to thwich nucleotides can be added. Therefore each round of DNA replication will yield shorter and shorter DNA molecules.
The solution. repeated DNA sequences at terminal ends. up to 2500 noncoding TTAGGG repeated sequences in tandem.
Telomerase can catalyze the formation of additional copies of telomeric subunits
Cancer cells produce telomerase in order to stabilize telomere length throughout rapid replication
Describe the sequence of events and enzymes involved in DNA repair process
Affected portion of DNA strand develops T-T bonding or C-C bonding dimer that is recognized and incised by an endonuclease enzyme
Exonuclease causes excision and broadening of gap
Gap filled by DNA polymerase I by repair replication
Synthesised DNA segment is joined by DNA ligase
Question number 11
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Question 13
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Define Chromatid
Chromosomes
Each chromosome consists of 2 chromatids joined by centromere or kinetochore. Only called a chromatid until division of centromere…then becomes chromosome.
Watch Mitosis and Meiosis videos
Okay
Define mutation and describe various types
An alteration in the DNA base sequence resulting in a change in the corresponding mRNA or protein.
Point, Silent, Missense, Nonsense , Frameshift
Deletion, Translocation, Insertions
List the factors that cause an increase in mutation rate and their effects.
Chemical agents
Ionizing Radiation
UV Light
Define inborn errors of metabolism
Abnormal functions in the body as a result of mutations in the genes, which are passed from generation to generation.
Phenylketoneuria (PKU)
Cause
Symptoms
Interventions
Autosomal recessive gene on chromosome 12
Increased phenylalanine in blood, mental retardation in kids, Epileptic seizures, lighter skin and hair color due to lack of melanin
Low phenylalinine diet must be started soon after birth screening takes place.
Galactosemia Cause
Symptoms
Interventions
Absence of galactose 1-P Uridyl transferase due to mutation
Increased galactose in blood, Hepatomegaly and jaundice, vomiting diarrhea when milk drank, mental retardation or death. Production of toxic galactitol.
Exclusion of galactose from diet after confirmed by amniocentisis
Alkaptoneuria Cause
Symptoms
Interventions
Absence of homogentisate oxidase due to mutation
Increased homogentiic acid in blood, black urine due to excess homogentisate, which turns black upon oxidation, calcified ear cartilage and arthritis like symptoms
None
Sickle Cell anemia Cause
Symptoms
Interventions
Missense mutation in Hb gene causing change in beta chains of Hb A
Sickled RBCs, Severe anemia, Widespread ischemia and infarction, Lymphnode swelling and kidney damage, Death by age 30 common
Use of antisickling agents
Describe the events in Chemical Carcinogenisis
Induction - seed tumor cell created from healthy cel
Promotion - Benign tumor becomes malignant
Progression - irreversible growth
