Exam 1 Flashcards
Genetics
branch of biology that deals with the heredity and variation of organisms
Human genetics
heredity and variation in humans
Medical genetics
subset of human genetic variation that is of significance in the practice of medicine and medical research
involves the application of genetics to medical practice
4 types of genetic diseases discussed in this class
1) Single gene disorders
2) Chromosomal disorders
3) Multifactorial disorders
4) Mitochondrial disorders
homologous chromosomes
posses genes for same characteristics at corresponding
gene locus
refers to specific location of gene on a chromosome
alleles
refers to different versions or forms of genes
represented by different DNA codes
humans have 2 copies of all their autosomal genes
homozygous
two identical alleles at gene loci
heterozygous
different alleles at the loci
genotype
individuals allelic constitution at locus
phenotype
observed characteristics of an individual, produced by interaction of genes with their environment
dominant
an allele that is expressed in the same way with a single copy as a double copy
recessive
allele that is pehonypically expressed as a homozygous (double copy) or hemizygous state
genome
totality of an organisms DNA
list of instructions encoded in DNA (needed to make a human)
made up of 3 billion bases of DNA split into 23 pairs
DNA sequencing
process of determining the exact order of bases (A,T, C, & G) in a piece of DNA
incomplete dominance
situation in which both alleles of a hertozygote influence the phenotype
typically somewhere intermediate between the two traits
ex. red and white make pink flowers
co dominance
situation in which a heterozygote shoes the phenotypic effects of both alleles fully and equally
ex. blood type
polygenic trait
an additive effect of two or more gene loci on a single phenotype character
ex. hair/eye color
4 laws of Heredity
Gregor Mendel
- law of uniformity
- law of segregation
- law of independent assortment
- Law of Dominance
punnet square
alternative method for determining genotypes in offspring
genetic code
combinations of mRNA codes that specify individual amino acids
codons
three nucleotide bases
coded by mRNA
wild type allele
DNA sequence of a gene that is associated with normal gene function
polymorphism
common differences in the DNA sequence
will have same function as wild type despite alteration of in gene sequence
types of polymorphisms
SNPs
tandem repeat polymorphisms (VNTRs and STRPs)
SNP
single nucleotide polymorphism
most ocommon type
variants at single nucleotide position on chromosome
tandem repeat polymorphisms
regions in the genome where the same DNA sequence is repeated over and over in tandem
include VNTRs and STRPs
reading assignment 1 (polymorphisms)
bc of large number of polymorphisms, each individual has their own DNA profile
can be ID by forensic science (PCR of sample DNA)
polymorphisms included in VNTR and STR
disease causing mutation
alterations in DNA sequence of gene associated with altered or absent gene function
double stranded helix
DNA
3 elements of DNA
phosphate
deoxyribose sugar
nitrogenous base
back bone of DNNA
phosphate and sugar groups that collect on outside
bases on inside
DNA bases
cytosine
adenine
thymine
guanine
Base paring
C –> G
A –> T
bonds that hold the base pairs together
hydrogen bonds
link nucleotides from one phosphate to the next
DNA coil levels
DNA coils around histone core =nucleosome
nucleosome coils = helical solenoid
solenoids coil into chromatin loops = chromosome
genes are arranged along ___
chromosomes
chromosomes
threadlike structures consisting of chromatin nd manuver DNA through cell division
how many pairs of chromosomes
23
22 pairs are autosomal and 1 set of sex chromosomes
diploid cells
somatic
contains two complete sets of chromosomes
consists of 23 homologous chromosome pairs, one set donated from ea. parent
mature diploid cells = how many chromosomes?
46 chromosomes (2n)
mature diploid cells = what division?
mitosis
haploid cells
sex cells
one copy of ea. chromosome (half the usual number)
typical state for gametes
after meiosis number of chromosomes in gametes is halved
mature haploid cell
how many chromosomes?
23 chromosomes (n)
mature haploid cell division?
meiosis
mitosis
part of the cell cycle by which chromosomes in the nucleus are separated into two identical sets of chromosomes each with its own nucleus
process of cell division for diploid cells
no crossing over
stages of mitosis
interphase prophase metaphase anaphase telophase
interphase
cell spends most of life here
DNA synthesis takes place
RNA and protein synthesis occurs
cell doubles in size
end of interphase:
cell has 2 ID copies of each of 46 chromosomes (92 total)
cells spend most of their life in which phase?
interphase
prophase
cell is full of chromatin and replicated
chromosomes are visible
sister chromatids are joined at the centromere
sister chromatids
two identical copies of chromosomes
joined at centromere during prophase
metaphase
chromosomes are most condensed now
EASIEST to visualize
centromeres line up at the equator thanks to spindle
anaphase
centromere of ea. chromosome splits
46 chromosomes are pulled to the side
telophase
nuclear membrane forms around ea. set of 46 chromosomes
result of mitosis
2 diploid daughter cells are created
meiosis
specialized division of sex cells
results in formation of egg and sperm
two sets of division
interphase I
replication of chromosomal DNA
cell suspends their time here
prophase I
homologous pairs of chromosomes become closely associated with their length via synapsis
forms tetrad
synapsis
joining of chromosomes
2 pairs of chromosomes v/2 chromatids ea.
metaphase I
2 pairs of chromosomes align on equatorial plane
forms the meiotic spindle
anaphase I
first division begin
two pairs of chromosomes are pulled to opposite ends of cells
telophase I
nuclear membrane reform and the cells complete division
equally in spermatogenesis (consisting of 2 chromatids)
results of meiotic division I
2 cells with 2 sister chromatids
interphase II
starts right after telophase I
no additional round of DNA synthesis
prophase II
chromatids join together at the centromere
metaphase II
chromosomes condense
anaphase II
chromosomes split at centromere
result of meiosis II
4 haploid cells
half the chromosome number
telophase II
differs in males and females
division of cytoplasm
spermatogenesis (telophase)
cytoplasm is divided equally among daughter cells
result: 4 equally functional haploid cells
continues throughout lifetime of males
oogenesis (telophase II)
unequal divisions of cytoplasm forming the egg cell and another polar body
result: 3 polar bodies with 1 functional ovum
different stages of oogenesis
primary oocytes are formed in utero, suspended in prophase I until puberty
onset of menses primary oocytes finish meiosis I during ovulation
meiosis II then proceeds after fertilization
how are chromosomes transmitted from parent to child?
replication of DNA (during fertilizations)
proteins coded by these genes are expressed via transcription and translation
gene
distinct sequence of DNA that codes for a particular protein
chiasms
points that chromatids attach
recombination
crossing over of chromatids at chasms
creates genetic variation
chromosomal crossover
exchange of genetic material between homologous chromosomes
prophase I of meiosis
occurs when regions of chromosomes break and attach to the other ones
genetic code
combinations of mRNA codons that specific individual amino acids
refers to how the nucleotide language of DNA gets translated and transcribed into amino acid language of proteins
DNA replication
DNA is copied during every division
DNA molecule unzips, exposing 2 parental stands and ea. strand serves as a template to develop the new strand
begins at multiple points with multiple separations
separation bubble
sites where the DNA strands separate
how does DNA direct protein synthesis?
through mRNA
gene expression
process by which the information encoded in a gene is used to direct the assembly of a protein
consists of transcription and translation
transcription
process of copying DNA into mRNA by enzyme RNA polymerase
occurs within the nucleus
DNA code is transcribed into a complementary mRNA molecule
SELECTIVE
mRNA
comprised of codons
mRNA processing
occurs before the primary mRNA molecules leaves the nucleus
excision of the introns from mRNA
then it leaves nucleus and enters cytoplasm to build proteins
translation
ribosomes bind mRNA/codons bind tRNA molecules
tRNA molecules add AA specific to the codon to build a polypeptide chain and give rise to a protein
what causes difference in DNA expression
different proteins expressed in different area of the body DNA can differentiate this
expressitivity
relative capacity of gene to affect the phenotype of organism
cofactors involved in DNA synthesis
RNA polymerase enzymes
promotor nucleotide sequences
enhancer/activators of silencer proteins
etc.
very complex and very regulated
source of genetic variation
mutation
advantages of mutations
- changes the DNA to get new forms of alleles
- would be no change w/o the
- mutations result in genetic variations
advantageous mutations are often passed onto next generation
disadvantage of mutations
may result in changes to cell function that causes death or disease
typically not preserved
gain of function mutation
good or bad
- results in gaining a new product
- can result in over expression of product
- can result in inappropriate expression of the product
often dominant disorders
loss of function mutation
- result in loss of product (recessive)
heterozygotes and loss of function
not effected by this unless there is a loss of more than 50% of product
otherwise the remaining alleles are still able to compensate
why do mutations occur
action of damaging chemicals or through errors in DNA replication processes
can change when DNA is undergoing replication
mutation causes
spontaneous
induced (radiation/chemcial)
spontaneous mutations
arise naturally during the process of DNA replication
induced mutations
caused by natural or human made agents
physical or chemical
alter structure or sequence of DNA
mutagens
agents that alter the DNA sequence
radiation mutagens
can be ionizing or non ionizing
ionizing radiation
charged ions are ejected from an atom and produce free radicals that cause damage to cells/DNA/lipid membrane
non ionizing radiation
NOT from charged ions
can move electrons from inner to outer orbits within an atom causes the atom to become chemically unstable
ex. UV radiant
UV radiation
non ionizing
causes formation of covalent bonds b/t the bases (instead of H)
gives rise to pyrimidine dimers
unable to pair properly with purines during replication = base substitution
can’t reach germ line cells but causes skin CA
chemical mutagens
can cause mutations in cells by altering DNAs structure:
forming base analogs, intercalating agent
base analogs
chemical mutagens
DNA bases are substituted with another
intercalating agents
chemical mutagens
physical insertion between existing bases
mutation repair mechanisms
body is good at repairing itself
damage reversal
damage removal
damage tolerance
damage reversal
simplest mechanisms
enzymatic action restores normal structure WO breaking the backbone
damage removal
cutting out and replacing a damaged or inappropriate base or section of nucleotides
damage tolerance
not true repair but way to cope with damage so life can go on
how often does mutation occur?
at nucleotide level
10^-9 per base per cell division
how often does mutation occur?
at gene level
variable
ranges from 10^-4 to 10^-7
mutation rate varies with:
- size of gene (bigger gene is more likely to be mutated)
- some nucleotide sequences are more susceptible
- age of parent during reproduction
cell type where can mutations occur?
- single germline cell
- exclusively somatic cells
- in some germline and some somatic cells
- in all cells
where do most mutations occur?
somatic cells
most of our cells are diploid so more mutations here
ex. cancer, aging
germline mutations
sex cells, mutation in sperm or ovum
the only mutations of genetic consequence that can be inherited
reading assignment
radiation exposure
Hiroshima and Nagasaki survivors
compared exposure of radiation
those closer to blast = higher exposure
abnormalities between group were insignificant
most of the results were problems on somatic cells not germline cells
mosaicism
refers to existence of two or more genetically different cell lines in an individual
mutation occurring in one cell of the embryo and all descendants of THAT cell have mutation
higher mosaicism = greater variability
disorders that are associated with mosaicism
trisomy 21
turner syndrome
Klinefelter syndrome
cause of alterations to genes or DNA sequences
alteration of single DNA base pair
alterations caused by gain or loos of entire chromosome
mutations of single base pairs:
mutations that take place in the coding DNA or in regulatory sequences
can’t be seen on microscopy
what happens if one of the bases is changed from C to A?
will have a significant impact on the amino acid
consequences of single base pair mutation
silent mutation non silent (nonsense or missense)
silent mutation
a mutation that is tolerated in most cases
no consequences of this
non silent mutation types
missense
nonsense
mis sense mutation
changes the codon to one that will encode for a DIFFERENT AA
may change the protein enough to cause ti to be unstable or structurally abnormal
nonsense mutation
changes the codon from encoding an AA to encoding a stop codon
base pair deletion or insertion can result
in extra or missing amino acid or protein
this is particularly problematic if the extra pairs are not multiple of three
frameshift mutation
when an insertion/deletion is NOT a multiple of 3
shifts the DNA base pairs
causes all the following AAs in sequence to be different, creating abnormal protein/none made at all
in frame mutation
occurs when insertion/deletion IS multiple of 3
changes only a few Das
may have functional protein
splice site mutaitons
alters the patterns of mRNA splicing
occurs at intron exon boundaries
promotor mutation
alters regulation of transcription or translation
can result in net increased or decreased gene expression
(regulatory region mutation)
Hemoglobin
found RBC carries oxygen from the lungs to the body tissues
2 alpha and 2 non alpha chains
non alpha chains
gamma chains (fetus)
beta chains (adults)
Hg F
2 alpha chains
2 gamma chains
HgA
2 alpha chains
2 beta chains
form adult hemoglobin 18-24 weeks
Hg A2
2 alpha chains
2 delta chains
beta chains (genes)
encoded by one gene on chromosome 11
alpha chains (genes)
encoded by 2 genes on chromosome 16
4 alpha global genes exist in ea. cell (each one responsible for 25% of HgB synthesis0
genese and HgB control
2 beta global genes express their protein in a quantity that is EQUAL to the four alpha global genes
2/4 contribute equally to production of subunit
hemoglobinopathies
single base mutations of human Hg
most common group of single gene dx
3 groups of hereditary hemoglobin disorders
- structural variants
- thalassemia
- hereditary persistence of fetal Hg
sickle cell anemia
gene mutation that causes it:
Single missense mutation of valine for glutamic acid at pos. 6 of beta globin chain
results in defective allele HgS
sickle cell
Pathophysiology of defect
- sickle cell crises – activity that boosts body’s requirement for O2 (illness, stress, altitude)
- hypoxia can cause severe pain during crisis
- chronic and progressive destruction in organs and tissues thru body due to infarctions
- molecules stick together and form long polymer chains which distort the cell and cause it to bend out of shape (tangled in vessles = infarctions)
- cells are destroyed (hemolysis) to get anemia
sickle cell inheritance patterns
Autosomal recessive
1 in 400 AA births
Presents in childhood damages to spleen most
sickle cell anemia advantage
-individuals with AS genotype have sickle cell trait phenotype; mis-shape and deflated RBCs, rarely develop severe anemic symptoms
- Advantage: sickle cell trait and dz have resistance to malaria b/c of deflated RBCs
- Disadvantage: sickle cell dx is deadly, SS genotype kills during childhood. Sickled cells are destroyed = anemia
hand foot and mouth syndrome
usually 1st symptom of sickle cell
Caused by clogging/infarcts, treat with pain meds and fluid
sickle cell patients are susceptible to…
Very susceptible to infection bc spleen is damaged
treat w/vaccines against penumo bacteria, prophylactic penicillin and hydroxyurea to increase HgbF
acute chest syndrome
sickle cell
occurs when lungs are deprived of O2 during crisis
treatment of sickle cell
Blood transfusions (reduce pain crises)
need chelation therapy to lower Fe levels
alpha thalassemia
gene mutation that causes it:
deletions of 1+ alpha globin genes on C16
results in reduced synthesis or stability of alpha chain; alpha globin gene fails
Trait 1-2 genes, Dx= 3-4 genes
alpha thalassemia pathophysiology (7)
- Decreased synthesis of one+ globin chains = imbalance in amounts of alpha chains.
Result is decreased O2 binding capacity, producing hypoxemia
- results in microcytic, hypochromic anemia
- imbalance in the ratio of alpha to beta chains (shortage of alpha and excess of beta)
- homotetramers form from excess B-chain
- affects both fetal and adult, bc BOTH fetal and adult Hg contain alpha chains
- severity of dx is dependent on number of alpha globin genes affected
thalassemia (alpha and beta) inheritance pattern
Autosomal recessive; occurs esp. among people in SE Asia and Mediterranean Basin
thalassemia advantage (alpha and beta)
those with thalassemia trait confer resistance to malaria
symptoms of alpha thalassemia
- Trait = not severe symptoms
- Disease = symptomatic, severe anemia and splenomegaly (3-4 genes)
HgbH Dx
3 dz genes
only one functional alpha globin gene
severe and transfusion dependent
lots of hemolysis
alpha thalassemia
Hydrops Fetalis
4 dz genes
typically dies as a fetus
incompatible with life
seen mostly in SE Asia
genetic cause Beta thalassemia
Single base pair substitutions in one or more B-globin gene at C11
results in reduced synthesis or stability of beta chain
beta globin gene fails
B-thalassemia pathophys (5)
- imbalance in amounts of beta chains
- microcytic hypochromic anemia
- imbalance in ratio of alpha to beta chains (shortage of beta subunits and an excess of alpha subunits)
- Homotetramers form from the excess alpha chains
- both globin genes are present in cell, but fail to produce HgB adequately
treatment B-thalassemia
correction of anemia by blood transfusion, control of iron accumulation via chelation, bone marrow transplant
minor B-thalassemia
trait
little to no symptoms, only if one beta gene fails
Diagnosed with HgB electrophoresis
major b-thalassemia
disease
occurs when both B-genes fail
produces severe anemia (Cooley’s Anemia)
Hereditary persistence of Fetal Hemoglobin
when the adult HgB fails to switch from gamma to beta
2 a and 2 g HgB
non treatable, typically benign
Hereditary persistence of Fetal Hemoglobin
pathophysiolgy
Impaired switching of globin synthesis
Defect in HgB switch mechanism
chromosomal mutation detection methods
FISH
karotyping
karyotyping
groups chromosomes based on relative sizes and legnths of 2 arms (p and q)
can count # of chromosomes and look for structural change to ID cause
cell is fixed with chemical and stained to reveal characteristic patterns
FISH
detects DNA sequence deletions of excess chromosome material using fluorescent labeled DNA segment
shows detection of tirsomy 21
cytogenetics
study of chromosomes and their abnormalities
centromere
where two chromatids are linked
p-arm
short arm of the chromosome
q-arm
long arm of the chromosome
telomeres
ends of the chromosomes
metacentric
when centromere occurs near middle of chromosome
submetacentric
centromere occurs b/t middle and tip of chromosome
acrocenteric
centromere occurs near tip of chromosome
chemical landing
ea. chromosome is numbered y bands from centromere out
band 9q34.1
1st sub band of 4th sub band of 3rd subdued of long arm of chromosome 9
read backwards
chromosome abnormalities are due to
abnormal number (loss of genetic material)
abnormal structure (relocation of genetic material)
euploid
normal set of chromosomes
polyploidy
extra set of the ENTIRE GENOME
not compatible with life, rare
aneuploidy
number of chromosomes is NOT a multiple of normal haploid number
most common type
MC cause of anyploidy
nondisjunction
nondisjunction
occurs commonly in older individuals
chromosomes are defective in pulling apart
can occur during meiosis I or meiosis II
nondisjunction in meiosis I
both homologous pairs go to same daughter cell, other gets none
nondisjunction in meiosis II
can result in monsomy or trisomy
2 normal haploids, 1 cell with 3 chromosomes and one cell with 1
autosomal aneuploidy
occurs to an autosomal cell
includes trisomy 21
monsomy
missing once chromosome pair
*45 total chromosomes
most incompatible
trisomy
one chromosome set consists of 3 copies instead of 2
47 total chromosomes
chromosomal structural mutations
deletions
inversons
duplications
translocations
deletions
loss of entire chromosomal segment and genetic material
disease caused by chromosomal deletions
Cri-du-chat
Wolf-hirschhorn syndrome
WAGR syndrome
Cri-du-chat
cry of the cat
characterized by high pitch cry
deletion on p of chromosome 5 (short arm)
Wolf hirschhorn syndrome
micro deletion of telemetric segment of 4p
classic greek warrior helmet face
WAGR syndrome
microdeletion of varying lengths along short arm of chromosome 11 (11p)
Wilms tumor, Anirida, Genitourinary abnormalities, Retardation
inversions
extra copy of chromosomal segment caused by break and reverse sequence (normal phenotype)
duplicaitons
less severe
chromosome segment is repeated producing extra alleles for a trait
ex. Pallister Killian Syndrome
Pallister Killian Syndrome
duplication
extra chromosome 12 material
usually mosaicism
severe mental retardation, polydactyly
translocation
exchange of chromosomal segments b/t two non homologous chromosomes
can run in family
two major types: robertsonian and reciprocal
Robertsonian translocation
short arms of two NON HOMOLOGUS acrocentirc chromosomes are lost
LONG ARMS fuse at centromere to form SINGLE chromosome
causes monosomy or trisomy
reciprocal translocation
occurs when breaks happen at 2 different chromosomes and genetic material is exchanged
carrier is unaffected but offspring had partial trisomy
Derivative chromosomes
trisomy 21
most common aneuploidy
90% nondisjunction occurs during meiosis I in oocyte
great survival rate into adulthood, 10% past 50
characteristics of trisomy 21
simian crease heart defects most men are sterile moderate to severe mental retardation (mosaicism) large tounge
trisomy 21 cause
extra chromosome in autosomal cells during meiosis
maternal age is only known correlating factor
edwards syndrome
trisomy 18
rare, most die in utero
unusually clenched fist
traced to nondisjxn in meiosis II of oocyte
Patau syndrome
trisomy 13
very rare, 1/2 die in first MOL
characterized by oral facial clefts and polydactyly
types of autosomal aneuploidy diseases
trisomy
downs syndrome/trisomy 21
edwards syndrome/trisomy 18
patau syndrome/trisomy 13
tuner syndrome
FEMALE always (45,X)
missing X chromosome
turner syndrome
characterized by
short stature
webbed neck
turner syndrome treatment
GH and estrogen to promote sexual development
Klinefelter syndrome
MALE (47, XXY)
characterized by taller than avg, low test score, *gynecomastia, reduced muscle mass
treatment: testosterone therapy
summarizes total number of chromosomes, types of sex chromosomes and types of aberration present
chromosomal shorthand
chromosomal shorthand
Normal Male
46, XY
chromosomal shorthand
normal female
46, XX
chromosomal shorthand
trisomy 21
47, XX+21 Female
chromosomal shorthand
edwards syndrome
trisomy 18
47, XX+18 OR 47, XY+18
chromosomal shorthand
turner syndrome
45, X
chromosomal shorthand
klinfelter syndrome
47, XXY
what may a family history show?
disorder is hereditary
clarify pattern of inheritance
enable you to determine risk of other family members developing condition
red flags in a family history
- unusual physical findings
- congenital or early onset deafness/blindness
- rare cancers/tumors
what questions must you ask when taking a family history
- sex of family member
- infection status
- relationship to other individuals
- biological relationship
first degree relative
related at parent offspring level or sibling
50%
second degree relative
removed by one addiotnal generation (grandparents, aunt/uncle)
25%
third degree relative
first cousin, great grandchildren (12.5%)
shorthand system of recording pertinent information about a family
genetic pedigree
starts with index case
index case
AKA proprand or propsita
individual present with you/you are evaluating
indicated with a P and arrow pointing to shaded circle
study the pictures of symbols on pedigree
:)
characteristics of Mendelian traits
single gene affected
clear pattern of inheritance
complete penetrance
5 pedigree patterns
- autosomal dominant
- autosomal recessive
- X linked recessive
- X linked dominant
- Y linked
autosomal dominant
vertical pattern
every generation has dz
features:
- both sexes
- at least on affected parent
- child of affected and unaffected =50% chance
autosomal recessive
horizontal pattern
parents are not symptomatic
features:
- both sexes
- 25% risk
- only one affected in one generation
X linked recessive
exclusively MEN
if mother is carrier they have 50% risk of dz
no male to male transmission
X-linked dominant
more female then male
all daughters of affected males are affected but no sones
Y linked
only males
always have affected fathers
penetrance
percentage of individuals having a genotype and expressing the phenotype
can be complete (always shows) or incomplete (do not show)
degree to which a phenotypic characteristic is exhibited
expression
can vary depending on factors
genomic imprinting
differential activation of genes
depending on which parent they are inherited from
uniparental disomy
condition in which persons inherit 2 copies of chromosome form 2 parent and no form other
ex. c15
example diseases of genomic imprinting
Prader Willi syndrome
Angelman syndrome
Prader Willi and ANgelman syndrome
both caused by deletion of 3-4 mil BP from 15q
depends on if this deletion is in mom or dad
Prader Willi syndrome
deletion is inherited from father
missing gene is active only on paternal C15 which encodes for RIBOPROTEINS
short stature and severe obesity result when this is deleted
most common GENETIC cause
Angelman syndrome
deletion inherited from mother
missing gene only active on maternal C15 which encodes for protein involved with protein deflation
secrete mental retardation (typically happy)
treated with ritalin
DNA mutation detection methods
protein electrophoresis
DNA amplification
microarray
protein electrophoresis
DNA segments are loaded into gel and electric current is applied
separates proteins based on size (small go further)
reveals DNA profile by evaluating polymorphisms
DNA amplification
PCR
duplicates genetic material at very fat rate
used to ID genetic fingerprints and detecting infectious dz
mircorarray
sophisticated way to isolate abnormalities
looks for activation of genes within cell using a chip
determine genes that turn on in response to treatment or infection
linkage analysis
diagnosed mapped genetic diseases
genes located along same region are transmitted together so you look for MARKERS on other genes
INDIRECT method
once linkage is established it can determine at risk individuals
markers
used in linkage analysis to find problems diseases
often short tandem repeat sequences
linkage analysis advantage
indirect diagnoses of at risk individuals
linkage analysis disadvantage
must test multiple family members
recombination can mess with results
direct mutation analysis
direct way to test if disease gene is known
diagnosis is made through direct ID of gene
direct mutation analysis advantage
no family information needed and no risk of error from recombination
direct mutation analysis disadvantage
must know which disease to look for
