Exam 2 Correlation Boxes Flashcards
DNA building block
deoxyribonucleotide
Deoxyribonucleotide
Composed of 2-deoxyribose with base (purine/pyrimidine) at 1’ position & phosphate at 5’ position
(Deoxy)ribonucleoside
Base plus (deoxy)ribose
(Deoxy)ribonucleotide
(Deoxy)ribonucleoside with 1 to 3 phosphate groups Base plus (deoxy)ribose with 1 to 3 phosphate groups
Nucleoside analog inhibitors (blue, p. 324)
Lack 3’-OH –> converted to dNTPs –> inhibit DNA replication
Examples: ara-C, acyclovir, AZT
Ara-C (arabinosylcytosine, cytarabine)
Nucleoside analog inhibitor containing the sugar arabinose
Animal cells convert to ara-CTP –> comp inh of DNA pol
Treats leukemia
Acyclovir (acyloguanosine)
Nucleoside analog inhibitor
Herpesvirus-encoded thymidine kinase catalyzes phosphorylation –> host enzymes convert mono-P –> tri-P
Lacks 3’-OH group, acts as chain terminator in DNA synth
AZT (azidothymidine)
Nucleoside analog inhibitor used in HIV therapy
Taken up by HIV-infected cells –> activated –> utilized by viral reverse transcriptase (RNA-dependent DNA pol)
Lacks 3’-OH group, acts as chain terminator in DNA synth
Xeroderma Pigmentosum (p 333)
Defect in NER complex (DNA repair process)
Skin extremely sensitive to sunlight, prone to developing melanomas & squamous cell carcinomas
UV light –> cyclobutane thymine dimers form in DNA (easily repaired in normal people by NER)
Hereditary nonpolyposis colorectal cancers (p 333)
Increased risk w/MER complex gene mutations (MSH2, MLH1)
Mutation in good copy of MER complex gene –> non-functional MER complex –> tumor allowed to develop
Cockayne syndrome (p 334)
Rare autosomal recessive, congenital disorder
Mutations in genes (ERCC6 & ERCC8) that are involved in TCR of DNA; if DNA not repaired –> cell dysfunction and cell death
Developmental and neurologic delay, photosensitivity, progeria; hearing loss/eye abnormalities; death occurs w/in first 20 yrs of life
Type A: ERCC 8, Type B: ERCC 6 (70% of cases)
BRCA associated Breast Cancer (p334)
Mutations in tumor suppressor genes (BRCA1 & BRCA2) –> 5x risk increase in women for breast/ovarian cancer before menopause (inc for men too)
BRCA1: Ass w/higher risk of cervical/uterine/pancreatic/colon cancer in women; pancreatic, testicular, & early prostate cancer in men
BRCA2: inc risk of developing melanoma & pancreatic, stomach, gallbladder, & bile duct cancer in women; pancreatic, testicular, & early prostate cancer in men (more often than BRCA1)
Transcription Factors (p. 341)
Trans-acting proteins that regulate gene transcription across chromosomes
Proteins that bind to many lipophilic hormones (steroid/thyroid hormones, vitamin D)
TF Deregulation (p. 348)
Causes inappropriate in/activation of cell growth genes –> oncogenesis/cancer
Can occur by aberrant increase in expression level or by coding sequence mutations that alter TF activity
TF homo/heterodimers
Can promote/repress transcription of target genes
Bind target sequences on DNA –> recruit other proteins (like RNA Pol)
TF regulatory hydrophilic molecules
Hydrophilic molecules that act at surface of cell via GPCR/receptor tyrosine kinase/receptor-ass kinase
Regulate gene expression, usually involving regulated phosphorylation
DNA-binding domains
Enable transcription factors to bind specific DNA sequences (response elements) in promoter/regulatory gene region
Promoter regions
Located immediately upstream of transcription start site
Regulatory sequences
May resides thousands of kb up/downstream from transcribed gene
Aberrant DNA methylation (p. 348)
Exemplified by FMR1: CGG expansion –> cytosine methylation –> region extends into promoter area –> transcription turned off
Oncogenes
Significantly represented by mutated TF genes
Increased TF expression level
Result of TF misregulation exemplified by an increase in number of gene copies
TF coding sequence mutations
Result of TF misregulation exemplified by loss of phosphorylation site required for regulated shutdown of TF activity
Preproinsulin to mature insulin (p. 363)
20-residue signal peptide cleaved in ER lumen –> pro insulin –> folds to form 2 intramolecular disulfide bridges –> passes through Golgi into beta granules –> cleaved to 33-residue C peptide (leaves behind mature insulin)
Fragile X Mental Retardation Syndrome
Gene encodes a protein involved in neurologic function
CGG expansion –> cytosine methylation –> region extends into promoter area –> transcription turned off
Gene is silent (even though triplet expansion occurs upstream of protein-coding region)
FMR1 gene
Encodes a protein involved in neurologic function
DNA sequence contains 30 repeats of CGG
Mutated DNA sequence contains >200 repeats of CGG
Preproinsulin
Made in pancreatic beta cells (single polypeptide w/104 AA’s)
PT collagen modification (p 364)
Inside cell: some lysines on precollagen –> 5-hydroxylysines –> some glycosylated w/gal & glc
Outside cell: some lysines/hydroxylysines oxidatively deaminated to aldehydic residues, some prolines on procollagen hydroxylated –> 4- & 3-hydroxyprolines
Essential to assembly/cross-linking of collagen helices
Need ascorbic acid
Mature insulin
Contains two peptides of 30 & 21 residues linked by 2 disulfide linkages
Stored in beta granules as Zn-bound hexamer until secretion
Produced/released in equimolar amounts to C peptide
Circulating C peptide
Produced/released in equimolar amounts to mature insulin
Immunoassay to assess pancreatic beta cell function (particularly in patients w/circulating anti-insulin antibodies)
Distinguish b/w hypoglycemic disorders due to islet cell tumors & facetious hypoglycemia
Islet cell tumors
Due to overproduction of insulin
Cause hypoglycemic disorders
Facetious hypoglycemia
Due to exogenous insulin infusion
Heterotrimeric type I collagen
Most abundant structural protein in vertebrates
Lysyl hydroxylase
Part of PT collagen modification, needs ascorbic acid
Mutations –> skin/bone/joint disorders (Ehlers-Danlos syndrome type VI, Nevo syndrome, Bruck syndrome type 2, epidermolysis bullosa simplex)
Prolyl hydroxylase
Part of PT collagen modification, needs ascorbic acid
Karyotyping (p 385)
Allows determination of the number, size & gross structure of metaphase chromosomes
Traditional gold standard cytogenetic method in identifying chromosomal abnormalities ass w/genetic disorders
Does not provide info at molecular level
Chromosomal Mutations (p 328)
Involve large segments of DNA (millions of bp’s)
4 types: inversion, deletion, duplication, translocation
Meiosis (p 368)
Process by which a diploid (2N) germline cell divides into haploid (1N) gametes
Occurs in 2 stages
Inversion
Type of chromosomal mutation in which a segment of chromosomal DNA is present in its reverse orientation
Deletion
Type of chromosomal mutation in which a segment of chromosomal DNA is lost
Duplication
Type of chromosomal mutation in which a segment of chromosomal DNA is copied, resulting in amplification of genes contained in that region
Translocation
Type of chromosomal mutation in which two different chromosomes exchange segments of their DNA
Can be either balanced or unbalanced
Balanced Translocation
Type of chromosomal mutation in which resultant hybrid chromosomes are similar in length to their normal counterparts
Unbalanced Translocation
Type of chromosomal mutation in which resultant hybrid chromosomes are dissimilar in length to their normal counterparts
Mitosis
Process by which a diploid (2N) somatic cell divides to produce 2 identical daughter cells, each of which also contains 2N amounts of DNA
Meiosis I
Following interphase, chromosomes divide as in mitosis
During prophase, duplicated homologous chromosomes pair up to form a bivalent (which has 4 chromatids, 1 for each chromosome), allowing homologous recombination
Cell division proceeds to generate 2 daughter cells (each has 1 unmodified parental chromosome and one recombinant chromosome)
Homologous recombination
Exchanging of fragments of maternal and paternal chromatids
Occurs in Meiosis I
Leads to genetic variation
Bivalent
Structure with 4 chromatids, 1 for each chromosome
Formed during prophase I when duplicated homologous chromosomes pair up to allow homologous recombination
Meiosis II
Sister chromatids in each cell separate to produce 4 gametes (each with 1N amount of DNA)
Does not involve any further DNA synthesis
Uniparental disomy (p 319)
Phenomenon when an individual receives 2 copies of a chromosome or part of a chromosome from 1 parent and no copies from the other parent
May occur as a random error in meiosis during the formation of egg or sperm cells or in early fetal development
Often asymptomatic because the individual has at least one copy of each gene
If in imprinted genes, there may be delayed development, mental retardation, and other medical issues (most well known is Prader-Willi syndrome w/chromosome 15)
Mosaicism (p 319)
Condition in which cells from an individual who has developed from a single fertilized egg have different genotypes
Caused by an error in cell division early in embryonic life
Percentage of normal to abnormal cells determines disease severity/symptoms/treatment, high %age mosaicism results in similar presentation to typical nonmosaic form of disease
Diagnosed with chromosomal or microarray analysis
Ex: Down, Klinefelter, & Turner syndrome
Prader-Willi syndrome
Involves the imprinting gene on the long arm of chromosome 15
Paternal gene is silenced
Dysfunction leads to uncontrolled eating and obesity
Mosaic Down syndrome
chromosome 21 trisomy in a %age of cells
Mosaic Klinefelter syndrome
some cells are normal/46XY, some have an extra chromosome/47XXY
Mosaic Turner syndrome
some cells are normal/46XX, some have a missing chromosome/45XO
Congenital disorders of glycosylation (p 365)
Caused by defects in assembly of 14-sugar oligosaccharide on phosphorylated dolichol (Type I) or in processing of to complex types of glycoproteins in Golgi (Type II)
1a (70%) caused by phosphomannomutase defect
1b caused by phosphomannose isomerase defect
CDG1a
Phosphomannomutase defect (mannose-6P –> mannose-1P) –> defective assembly of 14-sugar oligosaccharide on phosphorylated dolichol
CDG1b
Phosphomannose isomerase defect (fructose-6P –> mannose-6P) –> defective assembly of 14-sugar oligosaccharide on phosphorylated dolichol
Ascorbic acid
Essential for lysyl and prolyl hydroxylase activity
DNA content (p 366)
Resting mammalian cells in the G1 phase: DNA content of 2N
S phase: DNA content varies b/w 2N & 4N
G2 & M phase: DNA content doubled to 4N
After cytokinesis: back to 2N
Proteolysis of cyclins (p 368)
regulated mechanism to degrade transiently expressed cyclin proteins in order terminate activity of cyclin-CDK complexes
cyclins targeted by polyubiquitination
RAS and cancer (p104)
Mutant forms of mammalian RAS (or its GEFs & GAPs) have been implicated on a wide range of cancers (30-50% of lung/colon cancers, 90% pancreatic cancers)
Point mutations decrease intrinsic GTPase activity-> lock in active/GTP-bound state
Ex- neurofibromatosis (NF-1 gene encodes a GAP for RAS)
RB protein (p 371)
Discovered through examination of microdeletions in chromosome 13 in individuals with retinoblastoma
Hereditary form: 1 copy of gene mutated or lost in every cell & cells become predisposed to cancer (if good second copy is damaged by mutation, cells lose control of G1 checkpoint)
Nonhereditary form: cancerous cells contain different somatic mutations in both copies of the RB gene
Recognition domains (p 105)
SH2 or PTB domains on adaptor proteins that recognize and bind to receptor motifs that have phosphorylated Tyr residues
Ex- GRB-2, IRS-1
Small G proteins (p 105)
Transduce signals from plasma membrane receptors -> effector proteins (ex- kinases)
Intrinsic GTPase activity (mutations lead to cancer)
Control cell prolif, intracellular vesicular traffic, survival/apoptosis, cell shape/polarity, membrane transport, secretion
Monomeric
RAS superfamily w/>150 members, 20-25 kDa
Subfamilies: RAS, RAB, RHO, ARF, RAN
Fibrosarcomas in chickens (p 376)
Caused by Rous sarcoma retrovirus (RSV)
Transforming factor: v-src (Tyr kinase, oncogenic form of normal host Porto-oncogene c-SRC)
Replicative cell senescence (p 371)
Type of aging in somatic cell cultures
Due to progressive shortening of telomeres w/each cell division (especially if cells lack telomerase)-> DNA damage–> p53-mediated cell cycle arrest at G1 checkpoint
Ex- human skin fibroblasts in cell culture stop dividing after 30-50 population doublings, even when abundant growth factors are present in the culture medium
germline cells
contain 23 chromosomes (unpaired)
haploid
also known as gametes
ubiquitin ligases
catalyze targeting of cyclins for proteolysis
ubiquitinate CKIs to target for degradation, releasing the inhibition of S phase cyclin-CDK complexes
p53 and cancer (p 371)
More than 50% of all cancers exhibit mutations in p53
Examples of failed p53 activation: Li-Fraumeni syndrome, ataxia telangiectasia
Metabolic activation of benzo(a)pyrene–> potent mutagen
Activated benzopyrene & Aflatoxin–> p53 mutations by G->T transversions