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CYTOGEN FINALS > MIDTERM LEC 2: MODIFICATIONS OF MENDELIAN RATIOS > Flashcards

MIDTERM LEC 2: MODIFICATIONS OF MENDELIAN RATIOS Flashcards

1
Q
  • genotype ( allele combination) that causes DEATH, homozygous

Ex: Achondroplastic dwarfism
GENOTYPES: PHENOTYPES:
AA Lethal
Aa Achondroplasia
aa Normal Height

ratio:
1/4 die as embryos (AA)
survivors - 2/3 = achondroplasia (Aa), 1/3 = normal height (aa)

A

LETHAL GENOTYPES

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2
Q
  • 3 or more alleles of the same gene
  • different allele combinations can produce variations in the phenotype
  • simplest case: 3 alternative alleles of 1 gene exist

Ex: ABO blood group system in humans
- involves 3 alleles: Ia, Ib, and Io

A

MULTIPLE ALLELES

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3
Q

individual with 2 different mutant alleles with the same gene is called….

A

COMPOUND HETEROZYGOUS

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4
Q
  • characterized by the presence or absence of antigens (A & B) on the surface of RBCs
A

ABO BLOOD GROUP SYSTEM

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5
Q

ABO BLOOD GROUP SYSTEM is discovered by

A

KARL LANDSTEINER

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6
Q

When individuals are tested using antisera that contain antibodies against the A or B antigen, 4 phenotypes are revealed, either:

A
  • A antigen (A phenotype)
  • B antigen (B phenotype)
  • A and B antigen (AB phenotype)
  • or neither antigen (O phenotype)
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7
Q

reagent that is used to determine what antigens is preset on the RBC of an individual

A

ANTISERA

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8
Q

ABO blood group system in humans involves 3 alleles and these are….

A

Ia, Ib, and Io

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9
Q

the I designation stands for

A

ISOAGGLUTINOGEN

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10
Q

GENOTYPE: Ia Ia

ANTIGEN: A

PHENOTYPE:

A

A

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11
Q

GENOTYPE: Ia Io

ANTIGEN: A

PHENOTYPE:

A

A

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12
Q

GENOTYPE: Ib Ib

ANTIGEN: B

PHENOTYPE:

A

B

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13
Q

GENOTYPE: Ib Io

ANTIGEN: B

PHENOTYPE:

A

B

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14
Q

GENOTYPE: Ia Ib

ANTIGEN: A, B

PHENOTYPE:

A

AB

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15
Q

GENOTYPE: Io Io

ANTIGEN: Neither

PHENOTYPE:

A

O

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16
Q

______ are codominant (joint expression of both alleles in a heterozygote)

A

Ia & Ib

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17
Q

DIFFERENT DOMINANCE RELATIONSHIPS:
- 1 allele is expressed while the other is not
- Dominant allele completely masks the recessive allele
Ex: Mendel’s pea plants

A. COMPLETE DOMINANCE
B. INCOMPLETE DOMINANCE
C. CODOMINANCE

A

COMPLETE DOMINANCE

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18
Q

DIFFERENT DOMINANCE RELATIONSHIPS:
- partial dominance
- neither allele dominants the other
- heterozygous phenotype is an intermediate or blended expression of 2 alleles
- 3 genotypes = 3 phenotypes
ex: flower of snapdragon

A. COMPLETE DOMINANCE
B. INCOMPLETE DOMINANCE
C. CODOMINANCE

A

INCOMPLETE DOMINANCE

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19
Q

DIFFERENT DOMINANCE RELATIONSHIPS:
- different alleles are both expressed in a heterozygote
- neither allele is dominant over the other & both contribute to the observable characteristics of the organism
ex: ABO blood group

A. COMPLETE DOMINANCE
B. INCOMPLETE DOMINANCE
C. CODOMINANCE

A

CODOMINANCE

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20
Q
  • absence/ dysfunction of the beta-hexosaminidase A enzyme
A

TAY - SACHS DISEASE

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21
Q

TAY - SACHS DISEASE
- full enzyme level

A. HOMOZYGOUS DOMINANT
B. HETEROZYGOTES
C. HOMOZYGOUS RECESSIVE

A

HOMOZYGOUS DOMINANT

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22
Q

TAY - SACHS DISEASE
- intermediate level of enzyme

A. HOMOZYGOUS DOMINANT
B. HETEROZYGOTES
C. HOMOZYGOUS RECESSIVE

A

HETEROZYGOTES

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23
Q

TAY - SACHS DISEASE
- no enzyme

A. HOMOZYGOUS DOMINANT
B. HETEROZYGOTES
C. HOMOZYGOUS RECESSIVE

A

HOMOZYGOUS RECESSIVE

24
Q
  • effect of one gene masks or modifies the expression of another gene

ex: hh blood group (Bombay phenotype) = interaction between H gene and the I gene (confers ABO blood group)

25
building block for the production of the antigens within the ABO blood group
H antigen
26
- has/forms the H antigen
HH & Hh
27
hh individuals cannot produce antigens of the A & B, & appear to be O - type true or false?
TRUE
28
- all-or-none expression of a genotype - frequency of expression of disease phenotype in individuals with a gene lesion
PENETRANCE
29
TYPE OF PENETRANCE - gene(s) for a trait are expressed in ALL POPULATION who have the gene (100 %) A. COMPLETE PENETRANCE B. INCOMPLETE PENETRANCE
COMPLETE PENETRANCE
30
TYPE OF PENETRANCE - genetic trait is expressed only PART OF THE POPULATION (genotype is present but phenotype is not observable) A. COMPLETE PENETRANCE B. INCOMPLETE PENETRANCE
INCOMPLETE PENETRANCE
31
- severity/extent - range of phenotypes in individuals with the same gene lesion ex: polydactyly
EXPRESSIVITY
32
- if a protein affects different body parts or participate in more than one biochemical reactions or has different effects in different amounts - a single gene influences/controls multiple seemingly unrelated traits or phenotypic characteristics - a single gene has multiple effects on the phenotype of an organism - difficult to trace through families because people with different subsets of symptoms may appear to have different disorders ex: PORPHYRIA VARIEGATA (missing protoporphyrinogen oxidase enzyme)
PLEIOTROPY
33
PORPHYRIA VARIEGATA - missing protoporphyrinogen oxidase enzyme) - porphyrin accumulates in the
URINE, DIGESTIVE SYSTEMS, MUSCLES AND NERVOUS TISSUE
34
porphyrin accumulates in the Urine system results in
dark red urine
35
porphyrin accumulates in the digestive system results in
constipation and abdominal pain
36
porphyrin accumulates in the muscles results in
weak limbs and rapid pulse
37
porphyrin accumulates in the nervous tissue results in
delirium, convulsions, mad behavior
38
- mutation in different genes that produce the same phenotype - gene A and gene B has the same phenotype but since gene A mutates then it will produce different phenotype ex: blindness - mutation in more than 100 genes causes degeneration of the retina
GENETIC HETEROGENEITY
39
- an acquired condition that resembles a genetic condition or disease - caused by environmental exposures, infections,nutritional deficiencies , medications and other non-genetic factors ex: Limb birth defect caused by the drug THALIDOMIDE is a _________ of the inherited illness PHOCOMELIA (short limbs/ limb defects)
PHENOCOPY
40
WHAT PHENOMENON? - a phenotypic class DOES NOT SURVIVE to reproduce
LETHAL ALLELES
41
WHAT PHENOMENON? - many VARIANTS or degrees of a phenotype are possible
MULTIPLE ALLELES
42
WHAT PHENOMENON? - a heterozygote's phenotype is INTERMEDIATE between those of the two homozygotes
INCOMPLETE DOMINANCE
43
WHAT PHENOMENON? - a heterozygote's phenotype is DISTINCT from and not intermediate between those of the two homozygotes
CODOMINANCE
44
WHAT PHENOMENON? - one gene MASKS or otherwise affects another's phenotype
EPISTASIS
45
WHAT PHENOMENON? - some individuals with a particular genotype DO NOT HAVE THE ASSOCIATED phenotype
PENETRANCE
46
WHAT PHENOMENON? - A genotype is associated with a phenotype of VARYING INTENSITY
EXPRESSIVITY
47
WHAT PHENOMENON? - the phenotype includes many symptoms, with different subsets in different individuals
PLEIOTROPY
48
WHAT PHENOMENON? - An ENVIRONMENTALLY CAUSED CONDITION has symptoms and a recurrence pattern similar to those of a known inherited trait
PHENOCOPY
49
WHAT PHENOMENON? - genotypes of different genes cause the same phenotype
GENETIC HETEROGENEITY
50
- maternally inherited - sperm head does not include mitochondria - mitochondrion is found in the midsection
MITOCHONDRIAL GENES
51
what will happen when the mitochondria from sperm enter an oocyte?
They are usually selectively destroyed early in the development
52
features of mtDNA
1. circular, 15,569 bp, 37 genes (24 encode RNA molecules & 13 encode proteins that function in cellular proteins) 2. mutates than nuclear DNA because it has fewer types of DNA repair 3. inherited from the mother only 4. No DNA - associated proteins (histones) 5. mt genes are not interrupted by DNA sequences that do not encode protein 6. many copies per mitochondrion and per cell 7. mitochondria with different alleles for the same gene can reside in the same cell
53
- MITOCHONDRIAL MYOPATHIES (muscle tissues) - Affected tissue are those normally with many mitochondria (skeletal muscle - may also result from mutations in nuclear genes that are essential for mitochondrial function - HALLMARK: red-ragged fibers
MITOCHONDRIAL DISEASES
54
- Mutated mitochondria and normal mitochondria in the same cell
HETEROPLASMY
55
Forensics: to link suspects to crimes - can identify war dead & support or challenge historical records
mtDNA REVEALS THE PAST

CYTOGEN FINALS (11 decks)

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