Flashcards in Medical genetics final Deck (72):
what causes fragile X?
portion of X chromoosome dangels by a thread. unstable CGG repetition at Xq27
MC widespread single gene cause of autism?
MC form of mental retardation?
fragile X (1/1000 males)
what changes pre to full retardation in fragile X syndrome?
alien 3 syndrome, cause and genotype?
XYY, anaphase II of meisois II error in chromosome separation, 1/1000 males
taller than average males, not excessively violent
how do humans have most phenotypic variation with least genotypic variation among mammals?
epigenetics, epigenome and regulation
mostly male phenotype; with androgenous characteristics:
hypogonadism, low T, weaker muscles and reduced strength, taller, less muscle and fail and body hair, broad hips, weaker bones, low energy.
3 control points of chromatin stage regulation?
histone methylation, histone acetylation, other modification?
what are target sites for histone methylation and what do they do?
cystidine residues dinucleotide (CpG), which down regulate transcritption
what occurs with histone acetylation?
DNA does not get condensed. active transcription is increased
what else modifies histones?
chromatin vs nucleosome vs hsitone?
histone are the protein that organizes DNA for expression. chromatin is the form of the whole thin. nuccleosomes are the spool around which dna winds
introns vs extrons
non-coding, affect mRNA regulation vs coding areas of DNA which can be turned into proteins
can extrons be shuffled?
CGCG sequence do what?
target sequence for enzyme to cleave DNA
3 sources of regulating transcription?
promoters (CCATT or TATA boxes) - immediately before the gene
enhancers (transcription factors that bind enhancer regions) before the promoter region
what do RNA need to get in and out of nucleus?
most RNA for protein synthesis can only function outside nucleaus
why problem for RNA to get in and out of nucleus?
RNA is a large molecule and needs active transport
how RNA nuclear transport regulated? 2 sources of regulation
karyopherins are either importins or exportins and attach to RNA to move them trough nuclear pore complexes. Ran proteins GTPase proteins regulate the whole thing.
what are proto-oncogenes?
they are involved in nuclear transcription. code for proteins that regulate cell growth and differentiation. they have potential to become oncogenes
what level of tumor suppressor and oncogenes for cancer to develop?
TSG - two hit
oncogene - 1 ht
what three parts of cell cycle do onccogenes affect?
TSG and oncogene mutate. do they produce more or less protein?
oncogenes - more
tumor suppressor genes - less
regulate translation (4)
5' cap, 3' tail, removal of introns, splicing of exons, poly A binding proteins.
what do PABP do?
bring 5' and 3' together to enhance translation
what does 5' cap on mRNA do
regulates nuclear export, prevents degradation, promotes translation, prmotes intron excision
what does 3' tail do
proteins mRNA from destruction, promotes export, and translation
where are location of modications marked in epigenmic maps?
above BP sequences. altering, activating, repressing, winding/unwinding and
how does proximity affect gene linkage?
during meisis recomination of genetic info occurs. the closer the gene are the less likely the are to experience crossover and may be linked
how to assess distance between loci on chromosomes
recomindaiton frequency. further apart more recombination
4 types of DNA polymorophisms?
restricted fragment length polymorophism (RFLP), variable number of tandem repeats (VNTR), short tandem repeat polymorphisms (STRP), single nucleoptide polymorphism (SNP)
DNA of different lengths
which polymorphisms used in paternity testing and forensic analysis?
Variable number of tandem repeats and short tandem repeat.
difference between VNTR and STRP?
both repeating satellite area. STRP 2-6 bases long. VNTR areas flanked on both sides by a restriction site 20-70 bases long
which polymorphism is used in gene mapping?
STRP. they are throughout the chromosome and make variation for alleles.
what is amnioentesis?
a test for prenatal genetic testing. small sample of amniotic fluid is collected
what is fetal risk of amniocentesis?
what are 3 complicatoins of amniocentesis?
infection, bleeding, damage to amniotics sack
when is amniocentesis performed?
16 weeks gestation
BRCA 1 expressed where?
bRCA1 genetic location?
chromosome 17, region 2, band 1
BRCA 1 produces what compared to BRCA 2?
breast cancer type 1 protein which sould repair doubel stranded breaks in DNA, BRCA repairs single stranded DNA breaks
what gene does BRCA1 interact with?
RAD51 for aids in strang break repair
limitations of gene therapy 4?
1) short lived - cells rapidly divide, difficult to reach all cells
2) immune response
3) viral vectors - difficult to control
4) multigene disorders - more common and difficult to target all the areas
RNAi what does it do and target?
interference RNA inhibits gene expression or translation by neutralizing targeted mRNA
who does post transcriptional gene silencing? and who does it defend against?
RNAi. defends against paraistic and viral sequences
scientific application of RNAi
silences genes for knowdown studies to understand what each gene does
CA 19-9 cancer?
CA 125 cancer?
AFP cancer marker?
beta HcG cancer marker?
BRCA increased risk for 8 cancers?
melanoma, pancreatic, gall bladder, bile duct, stomach, laryngeal, leukemia, and lymphoma?
BRCA 1 increase fro which 3 cancers?
ovarian, fallopian tube, prostate
gene control can be regulated at what 5 stages?
post translation control in cytoplasm
post translational modicfication
study of allele frequency change = evolution; distribution under influence of evolutional proceses
4 ievolutional proceses influence population genetics?
natural slection, genetic drift, mutation, gene flow
how does genetic drift influence allele freq?
how does gene flow influence allele freq?
exchange of genes btw population that live near each other
gene mutation are they harmful?
yes 70% harmful
how does natural selction influence allele?
promotes those that increase survival
what is founder effect?
when population begins with only a few individuals. less geentic variability
what is hardy weinberg?
mendelian genetic stability in absence of evolutionary processes. without the process we can anaylyze how much those processes are working
what is only monsomy consistent with life?
what is karyotype of turner?
45 X 50%, 46 XX, or 47 XXX
what is phenotype of turner syndrome?
short stature, ovarian dysgenesis,
how like to get breast cancer BRCA stats lifetime?
60% to 80% risk BRCA 1
40-70% BRCA 2
what may be responsible for fanconi anemia?
BRCA 2, with AML, and bonemarow failure by 40, endocrine problems, as well as congenital defects
how like to get ovarian BRCA stats lifetime?