Exam 2 Flashcards by Brad Francis

What are the 4 types of Chromatin?

Euchromatin (less dense and active)

Heterochromatin (condensed and inactie)

Perinucleolar Chromatin

Intranucleolar Chromatin

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Functions of the Nucleus

Command center

Reproduction
Heredity
Moment by moment functions of all cells

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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

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What is a gene?

Segment of DNA that determines sequence of amino acids in a protein.

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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

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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

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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

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Watch Transcription, Translation, Replication videos

OKAAY

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A typical protein coding gene has which three elements?

A core promoter

Proximal control elements

A transcription unit

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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

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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

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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

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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.

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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

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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

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Requirements of Activation

Inatitation?

Elongation?

Termination?

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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

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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

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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

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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

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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?

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End-Product inhibition.

Five levels of gene regulation

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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

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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 ????????

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

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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

Exam 2 Flashcards

(41 cards)