midterms 25% Flashcards
● A condition when during the heterozygous
condition (Bb) the dominant allele does not
completely overpower the recessive allele.
● Therefore, there is a “blending” of the traits.
incomplete/partial dominance
A condition when during the heterozygous
condition (Bb) the dominant allele does not
completely overpower the recessive allele so
both traits are seen at the same time.
- No recessive allele at all
codominance
This occurs when both alleles are
expressed equally in the phenotype of the
heterozygote.
Codominance
● Inheritance pattern for traits that are controlled
by more than one gene.
● An example would be: height, skin complexion,
eye color, hair color, etc.
polygenic inheritance
● Genes capable of causing death of organism
carrying them
- Typically the consequence of mutation
lethal genes
Manx cats are heterozygous for a dominant mutation that
results in no tails (or very short tails), large hindlegs, and a distinctive gait. The mating of two Manx cats yields two Manx kittens for each normal, long-tailed kitten, rather than 3:1 as would be predicted from Mendelian genetics. Therefore, the mutation causing the Manx cat phenotype is likely a(n)
_____ allele.
a. Codominant
b. Epistatic
c. Lethal
d. Sex-linked
lethal
● When one gene affects multiple characteristics.
● It refers to the expression of multiple
traits by a single gene.
Pleiotropy
- The transmission of traits through cytoplasmic genetic factors such as mitochondria or chloroplasts.
■ These cytoplasmic organelles are usually inherited with the egg’s cytoplasm from the mother
● Maternal inheritance (also called cytoplasmic
inheritance)
- An individual’s phenotype is controlled
by gene products in the genome (e.g.
proteins) of the mother (oocyte).
Maternal effects (also called maternal
influence)
A cell with a mutant and normal
mitochondria
heteroplasmy
A cell has a uniform set of
mitochondria: all completely
normal mtDNA or completely
mutant mtDNA
homoplasmy
Only the mother pass on the
mitochondrial DNA
true or false
true!
- a complementary cross
between the phenotypes of the female and the
male
Reciprocal cross
● Refers to the inheritance of an agent
(microorganisms, parasites, viruses, bacterias,
etc.) that can be inherited with cytoplasm.
INFECTIOUS INHERITANCE
_______ are formed due to the differential
methylation of paternal and maternal alleles.
Imprints
- low levels of gene
expression - Genes are imprinted
- Not expressed at all
Methylated DNA
- higher level of gene
expression - Genes are not imprinted
- Will be expressed
Unmethylated DNA
Presence of two or more populations of cells
with different genotypes in one individual who
has developed from a single fertilized egg.
mosaicism
This can be a result of X-inactivation or
mutation
- Both could lead to the development of
multiple cell populations
mosaicism
It develops during early
stage of embryonic development
(development of multiple cell
populations)
Mosaicism
it can be seen usually on the
later stage of life or when the individual
was already born
Vitiligo
refers to the
marking process in which an offspring
expresses a gene that is inherited from
one parent but not both.
Genomic Imprinting
used to analyze the patterns of
inheritance of a particular trait that runs in the
family.
Pedigrees
Use a__________ if the gender is not yet known, a
circle or a square if the gender is known.
diamond
○ If the trait is ________, one of the
parents must have the trait.
dominant
__________ traits skips the generation of
the affected family.
Recessive
✔ Only males are affected
Sex linked
✔ Parents doesnt have to be affected
✔ Skips generation (meron sa anak, sa parent
wala)
Sex linked recessive
✔ Does not skip a generation
Autosomal dominant
- One mutated copy of the gene in each cell is
sufficient for a person to be affected - Each affected person usually has one affected
parent
Autosomal dominant
- Two mutated copies (homozygous) of the gene
are present in each cell - Affected person usually has unaffected parents
who each carry a single copy of the mutated
gene (and are referred to as carriers)
Autosomal recessive
● Associated diseases are located in the X
chromosomes
X-LINKED DOMINANT INHERITANCE
- Always expressed in the males
- Expressed in a female homozygote but very
rarely in a heterozygote
X-linked Recessive trait
● Only males are affected
● It is based from father to all sons
- Because it is y-linked
● It does not skip generations
Y-linked Dominant
● Appears in both sexes with equal frequency
● Trait tend to skip generations
● Affected offspring are usually born to unaffected
parents
Autosomal Recessive
If most of the males in the pedigree are
affected, then the disorder is ?
X-linked
If it is a 50/50 ratio between men and women
the disorder is?
autosomal
● Both males and females are affected; often more
females than males are affected
● Does not skip generations.
● Affected sons must have an affected mother
X-linked Dominant
● Affected daughters must have either an affected
mother or an affected father
● Affected fathers will pass the trait on to all their
daughters
● Affected mothers if heterozygous will pass the
trait on to 1/2 of their sons and 1/2 of their
daughters
X LINKED DOMINANT
● It is NEVER PASSED FROM FATHER TO SON
● All daughters of affected fathers are carriers
X LINKED RECESSIVE
occurs when a homologous
pair of chromosomes fails to disjoin or separate
during cell division.
Nondisjunction
________ NONDISJUNCTION
● Failure of the chromosomes to disjoin and pass
to opposite poles
● Major cause of chromosomal abnormalities
MEIOTIC
● 75% occurs in oogenesis, where the
probability of nondisjunction increases with
maternal age
● Almost 80% occur in the first meiotic division
meiotic nondisjunction
During this stage, sister copies of DNA are
supposed to break apart and chromosomes are pulled
by the spindle
Anaphase
describes the chromosomal
complement of an individual.
Karyotype
petit, short arm
p
p-arm
○ Region 1
■ Contains __ band
1 band
p-arm
○ Region 2
■ Contains __ bands
2 bands
q-arm
○ Region 1
■ Contains __ bands
3 bands
q-arm
○ Region 2
■ Contains __ bands
8 bands
69, XXX ; 69, XXY ; 69, XYY
- 3 sets of chromosome
- Happens when ovum is fertilized by 2
sets of sperm
TRIPLOIDY
4, XX,+21
- Gain of 1 chromosome
TRISOMY
45,X
- 1 chromosome is missing
MONOSOMY
47,XXX / 46,XX
- 2 population of cells: 1 with trisomy, 1
normal cells
MOSAICISM
________ deletion - 1 break in the chromosome
→ chromosome segment distal to the break gets
detached and is lost
Terminal
_________ deletion - 2 breaks in the
chromosome → chromosome segment distal to
the break gets reattached
Interstitial
● 2 breaks in the chromosome arm (pwedeng both
arm or isang arm lang)
● Nagflip upside down yung segments tsaka siya
nag reattach
INVERSION
When the inversion involves BOTH arms and involves the centromere
PERICENTRIC INVERSION
When the inversion involves ONLY ONE arm
PARACENTRIC INVERSION
This involves the long arm of chromosome 1 region 2 band 2; has two segments
duplication
● The chromosome break, another chromosome
break
translocation
● The break occurs in the arm and they are fused
with each other
● The fragment that was cut off are lost during cell
division and it loses genetic material
ring chromosome
46.XY,r(9)(p12q21)
RING CHROMOSOME
formed when you have 1 break on its
arm: both in short and long arm, and the two
ends of the two arms fuse together because
they are sticky forming a ______ at the centromere
ring chromosome
46,XX,del(5)(q13q33)
interstitial
46,XY,del(4)(p16.3)
terminal
Abnormalities based on cell chromosomal
constituent are
1.
2.
○ Constitutional
○ Somatic or acquired
________ ABNORMALITY
● Found in ALL cells of the body
● Occurs very early in development
CONSTITUTIONAL
_________ ABNORMALITY
● Present only in CERTAIN tissues or cells
● Cell types with different chromosome
compositions
SOMATIC OR ACQUIRED
Abnormalities in chromosomes are produced
by the following, EXCEPT:
a. Misrepair of broken chromosomes
b. Improper recombination
c. Erroneous segregation during cell
division
d. DNA mutation
DNA MUTATION
Nondisjunction that occurs during meiosis II
will NOT result in which of the following
chromosome number in the zygote?
a. Normal
b. Monosomy
c. Nullisomy
d. Trisomy
NULLISOMY
Meiotic nondisjunction is more commonly
seen among which of the following?
a. Increasing maternal age
b. Increasing paternal age
c. Post-radiation in the young
d. Maternal infection
Increasing maternal age
Single gene mutation is increased in which
of the following?
a. Oogenesis in elderly women
b. Spermatogenesis in elderly men
c. Both
SPERMATOGENESIS IN ELDERLY MEN
Which of the following outcomes of
anaphase lag is almost always not
compatible with embryogenesis or live birth?
a. Monosomy of sex chromosomes
b. Trisomy of sex chromosomes
c. Monosomy of autosomes
d. Trisomy of autosomes
Monosomy of autosomes
GIVE THE KARYOTYPE
Female with classic Trisomy 21
47,XX,+21
Give the karyotype of Male with terminal deletion of chromosome 3, short arm, region 2, band 3, sub-band 1
- 46,XY,del(3)(p23.1)
45,X means
a female with monosomy X
Karyotype of a female with triploidy
69,XXX / 69,XYY
Karyotype of a female with triploidy
69,XXX / 69,XYY
A female with balanced reciprocal
translocation with breakpoint in the long arm
of chromosome 7, region 2, band 3 and the
short arm of chromosome 10, region 3 band
2 sub-band 1
- 46,XX,t(7;10)(q23;p32.1)
individuals with a normal set of
chromosomes; no extra or missing; normal
human somatic cells are diploid, with two sets of
23 chromosomes
Euploidy
- with extra sets of chromosomes;
caused by fertilization of an egg by > 1 sperm;
not compatible with life; e.g. triploidy (69,XXX).
Polyploidy
- two or more genetically different
cell lines
Mixoploidy
- with two cell populations
originating from the same zygote
Mosaic
- arise from two different zygotes
Chimera
- missing a pair of homologs
occuring during the preimplantation stage; lethal.
○ During this stage, baby may be aborted
Nullisomy
- one chromosome missing; occurs
during embryonic stage; lethal and abort in 99%
of cases;
Monosomy
- one chromosome missing; occurs
during embryonic stage; lethal and abort in 99%
of cases;
Monosomy
- gain of one chromosome: occurs
during embryonic (1-2 weeks) or fetal (9-36
weeks) stage;
Trisomy
In NONDISJUNCTION,
1st Meiotic division results to = __ normal zygotes, 1
trisomic, __ monosomic
2 normal zygotes, 1 trisomic, 1 monosomic
In NONDISJUNCTION,
2nd Meiotic division = __ trisomic zygotes, 1
monosomic
1
● May occur at G1 (affects both chromatids) or
G2 (affects one chromatid) phase of cell
cycle.
STRUCTURAL ABNORMALITIES
_____systems in the cell recognize and repair
broken chromosomes
Enzyme
Repair can be either by joining the two ends or
??
capping ends with telomeres
-
healed by adding telomere, if near the
telomere
Single break (terminal deletion)
- ring chromosome formation, duplication, interstitial deletion, inversion, translocation
Two or three breaks
two breaks -> broken portion turned
upside down -> reattached
○ No loss or gain of genetic material ->
inversion carriers, normal
INVERSION
- inversion of a
segment of the p or q arm and DOES NOT
include the centromere
Paracentric inversion
- breaks occur in
both short and long arms and INCLUDES
the centromere in the inverted segment
Pericentric inversion
- loss of a segment of a chromosome;
2 breaks between the centromere and telomere
-> loss -> fusion of broken ends
Deletion
- transfer of a chromosome
segment to another chromosome
Translocation
involves exchange of genetic materials of non-homologous chromosomes
○ No loss or gain of chromosomes but with gene rearrangement -> physically And mentally normal
Reciprocal or balanced translocation -
_________ translocation - involves
acrocentric chromosomes which have short p
arms called satellites
Robertsonian
_________ translocation - involves
acrocentric chromosomes which have short p
arms called satellites
Robertsonian
Robertsonian translocation - involves
acrocentric chromosomes which have short p
arms called ?
Satellites
○ The two p arms or satellites are lost because they are not attached to a spindle fiber during mitosis
○ Total chromosome is 45 due to fusion of the two chromosomes
Robertsonian translocation
Acrocentric chromosomes are __ 14,
15, __ and __ with short arms
(satellites) made up of rRNA
13, 14, 15, 21 AND 22
-
occurs when the exchange of chromosome
material is UNEQUAL resulting in loss or gain of
genes
○ Causes significant clinical outcomes
Nonreciprocal or unbalanced translocation
- chromosomes with two identical arms
○ Arms mirror image of each other; both p or q arms
Isochromosomes
● Study of chromosomes and their heredity
● The study of the physical size, structure,
and behavior of chromosomes.
CYTOGENETICS
○ Dark stain regions -
heterochromatin
Lightly stain regions -
euchromatin
○ Dark bands
○ Heterochromatic
○ Rich in the base pairs A-T (Adenine
and Thymine)
○ Devoid or with inactive genes
G-BANDS
○ Pale or bright bands
○ Euchromatic
○ Rich in G-C (Guanine and Cytosine)
○ Genes actively expressed
G negative bands
○ Pale or bright bands
○ Euchromatic
○ Rich in G-C (Guanine and Cytosine)
○ Genes actively expressed
G negative bands
● Fluorescent dye (Quinacrine, DAPI,
Hoeschst 3328)
● Patterns are similar to G banding
● Uses fluorescent microscope
Q-BANDING
● A-T rich (fluorescing, heterochromatin)
● G-C rich (light regions, euchromatin)
● Applied for rapid ID of Y chromosome in
uncertain genitalia
Q-BANDING
● Reverse of G-banding pattern
● Chromosomes are denatured by heat
before staining with Giemsa
● Patterns are similar to G banding
R-BANDING
● Heat denatures = A-T rich (bright)
● Dark regions - G-C rich (euchromatin)
● Used to detect deletion of telomeres
which are dark bands
R-BANDING
● Severe heat prior to staining (Giemsa or
combination of dye and fluorochromes)
● Identifies telomeres
T-BANDING
● Giemsa
● Treated with alkali solution
● Stains centromeres
C-BANDING
○ Most common SPECIMEN USED FOR
CYTOGENETIC TECHNIQUES
○ Preferred specimen for routine
cytogenetic studies of adult and
children
Heparinized peripheral blood
○ Used in studying hematologic disorders
Bone marrow aspirates
○ Used in Fibroblast cultures
Skin biopsies
○ Most common specimen for prenatal
analysis
Amniotic fluid
Fetal blood from the umbilical cord
○ Useful in ??
rapid karyotyping
Chorionic villus is used for
prenatal analysis
Chorionic villus is used for
prenatal analysis
Tissues such as kidney, liver, muscle, and lung should be handled and transported with?
ice
Excellent sources if obtained soon after death during autopsy or from a fetal loss
Tissues such as
kidney, liver, muscle,
and lung
○ Single enzyme or multiple enzymes
synthesize copies of target nucleic
acid
Target amplification
○ Most mature and widely used nucleic acid amplification method
○ In vitro chemical reaction that permits the synthesis of essentially limitless quantities of a targeted nucleic acid sequence
○ Uses DNA polymerase
Polymerase Chain Reaction
○ Amplification products contain a sequence only present in the initial probes
Probe amplification
○ The concentration of the probe or target does not increase
○ Concentration of label molecu;es attached to target nucleic acid increases
○ Uses multiple enzymes and probes with reduction of background noise to enhance target detection
Signal amplification
A heat-stable DNA polymerase
An equimolar mixture of dNTPs
- (dATP, dCTP, dTTP)
pcr
● DNA polymerase synthesizes a new DNA strand complementary to the DNA template in 5’ to 3’ direction
Extension/Elongation (72°C)
● Cooled to permit the primers to anneal the target DNA in a sequence specific manner
● Polymerase binds to the primer-template hybrid and begins DNA synthesis
Annealing (50 - 65°C for 20-60 secs)
● Reaction mixture is heated to separate 2 strands of target DNA
Denaturation (94 - 98°C for 20-30 secs)
● Amplify ribonucleic acid (RNA) targets
● Complementary (cDNA) is produced first
from RNA targets, then cDNA is amplified
by PCR
● Detection/quantification of hepatitis C virus
(HCV) RNA and HIV-1
rt pcr
● Target amplification and detection steps
occur simultaneously in the same tube
● PCR product is detected as it is
produced
REAL-TIME (HOMOGENOUS, KINETIC)
POLYMERASE CHAIN REACTION
● Fluorescent dyes that preferentially bind to
double-stranded DNA (dsDNA)
● Decrease time required to perform nucleic
acid assays because there are no
post-PCR processing steps
REAL-TIME (HOMOGENOUS, KINETIC)
POLYMERASE CHAIN REACTION
● Use of DNA probes on a chromosome spread.
● Used to detect and localize the presence or
absence of specific DNA sequences on
chromosomes
FISH
________FISH
- Uses a computer assisted system
- E.g: Dual fusion probes
Multicolor
________Karyotyping (SKY)
- Identify the chromosome using chromosome with same colors
- Multiple chromosomal aberrations
- White arrows identify some of the chromosome translocations
Spectral
- Uses a telomere probe → recognize 6 base repeat present at the ends of the chromosome
- Confirms the presence or absence of telomeric regions
ALL-TELOMERE FISH
- Involves only co-hybridization of 2 DNA samples
- Detects the copy number variation (CNV) of a DNA sequence
Comparative Genomic Hybridization
- Directly compares the DNA content
of differentially labeled normal and
tumor cell population by their
co-hybridization to normal
metaphase chromosome spreads
Comparative Genomic Hybridization
○ Comparison of labeled normal and tumor cells by their hybridization to a series of genomic oligonucleotides
aligned on a glass slide that serves as probes
○ Hundreds to thousand of features can be placed in 1 solid surface
Microarray Hybridization/DNA Chip
Technology
● Injection of a monodisperse suspension of particles (cells) into the center of a flowing stream of fluid (sheath)
● Passing through a small quartz capillary tube at a constant velocity
FLOW CYTOMETRY
● Light scattered by the particle is collected by detectors positioned at a variety of angles Around the capillary
● Cross-sectional area, and size or complexity/granularity of the particle
● Fluorescent molecules or fluorochromes may be attached to the particles and are excited by the incident light → fluorescent emission
FLOW CYTOMETRY
_________ at different angles - can
distinguish difference in size and internal
complexity
Light scattering
Light emitted from fluorescent labeled
particles or antibodies - can identify cell
surface and ?
cytoplasmic antigens
_________ cells express patterns of antigen
that are distinctly different from those of
their normal counterparts
Neoplastic
Which of the following karyotypes show euploidy?
a.46, XX
b.69,XXX
c.45,X
d.47,XX,+21
46,xx
The karyotype 46,XX,del(10)(q26.1q26.3) is an example of which chromosomal structural abnormality?
interstitial deletion
The cells are committed to advance further into the cell cycle after passing through which point in the cell cycle?
G1 RESTRICTION POINT
Which of the following structural chromosomal abnormalities result in significant loss of genetic information?
a.Balanced reciprocal translocation
b.Ring chromosome formation
c.Duplication
d. Inversion
RING CHROMOSOME
Nondysjunction occurring during the first meiotic division can give rise to which of the following zygotes?
a.Both of the given options
b.Normal
c.Neither of the given options
d.Trisomic
TRISOMIC
This is what we call to an individual if he/she is known to have symptoms of the disease or trait
AFFCTED INDIVIDUAL
The affected individual that brings the family to the attention of a geneticist is called:
PROBAND
- check for DNA damage
o If present, it will stop the cell cycle allow the cell to repair and continue the cell cycle
G1-S checkpoint
- check for damaged or unduplicated DNA
G2-M checkpoint
Which of the following is true in constitutional abnormality?
a.An acquired abnormality
b.Occurs late in the development
c.Seen in mosaicism
d.Found in all cells of the body
d.Found in all cells of the body
A mutation in the mitochondrial DNA may lead to the following diseases, EXCEPT:
A) MELAS
B) Encephalopathy
C) Myopathy
D) Renal cancer
d renal cancer
Alternative forms of genes are called
alleles
