Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BMS2.01 Single Gene Inheritance (CORBETT) > Patterns of Single Gene Inheritance > Flashcards

Patterns of Single Gene Inheritance Flashcards

1
Q

Locus definition:

A
  • physical site or location of a specific gene on a chromosome
  • two alleles for each locus (one each on each parental chromosome)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Genotype definition:

A
  • set of alleles present at a single locus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Phenotype definition:

A
  • observable expression of the genotype
  • Can be:
    • biochemical
    • cellular
    • physical (clinical)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Single gene disorders are:

A
  • diseases caused by mutations in a single gene.
    • significant disease burden on society, especially in neonates and pediatrics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Homozygous definition:

A
  • both alleles are the same
    • i.e. both wild type or both mutant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Heterozygous definition:

A
  • one allele is wild type
  • one allele is mutant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Compound heterozygous definition:

A
  • both alleles are mutant, but mutations on each chromosome are at different parts of the gene
    • ex: cystic fibrosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Hemizygous:

A
  • abnormal gene is located on chromosome X
    • note: male patients only have a single X chromosome (XY)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Allelic heterogeneity definition:

A
  • DIFFERENT MUTATIONS IN THE SAME GENE result in the SAME clinical phenotype
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Phenotypic heterogeneity definition:

A
  • DIFFERENT MUTATIONS IN THE SAME GENE result in VERY DIFFERENT clinical phenotypes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Locus heterogeneity definition:

A
  • MUTATIONS IN DIFFERENT GENES (at distinct loci) CAN result in the SAME CLINICAL PHENOTYPE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Mendelian diseases:

A
  • follow one of four classic inheritance patterns
  • occur in fixed and predictable proportions in offspring
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Pedigrees are used to:

A
  1. establish the pattern of inheritance of single gene disorders
  2. determine degree of risk of disease in offspring

determined by family history

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Four factors that can confound pedigree interpretation:

A
  1. early lethality of disorder
  2. small family size
  3. variable age of onset; decreased penetrance or variable expressivity
  4. non-Mendelian inheritance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Male pedigree symbol:

A

square

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Female pedigree symbol:

A

circle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The two factors that determine pattern of inheritance of single gene disorders:

A
  1. whether phenotype is dominant or recessive
  2. chromosomal location of gene locus
    • autosome
    • sex chromosome (X or Y)
    • mitochondrial genome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Does the mitochondrial genome follow Mendelian inheritance?

A
  • No
  • always inherited from mother
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the four major patterns of Mendelian inheritance?

A
  1. autosomal recessive
  2. autosomal dominant
  3. X-linked dominant (very rare)
  4. X-linked recessive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Autosomal recessive disease genotype:

A
  • must have two mutant alleles and no wild type
    • the type of mutation in each allele can be different (i.e. compound heterozygote)
  • rare
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Effect of mutant alleles in autosomal recessive disorders:

A
  • reduce or eliminate function of gene product
  • often affect enzyme function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What type of inheritance is this?

(b is mutant allele)

A

autosomal recessive

  • bb has disease phenotype
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Risk that a child of either sex will be affected in autosomal recessive inheritance:

A

1/4 (25%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Risk that a child of either sex will be a healthy carrier in autosomal recessive inheritance:

A

1/2 (50%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Risk that a child of either sex will not be affected in autosomal recessive inheritance:

A

3/4 (75%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Four factors that affect the risk of inheritance of a autosomal recessive disorder:

A
  1. carrier frequency (how prevalent carriers are)
  2. consanguinity (closely related)
  3. inbreeding (small population)
  4. genetic isolates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are the five key features of an autosomal recessive pedigree?

A
  1. parents unaffected carriers
  2. males = females
  3. recurrence risk to unborn sibling of an affected individual is 25%
  4. phenotype found in siblings
  5. rare trait = likelihood of consanguineous mating
28
Q

What type of inheritance is this?

(B is mutant allele)

A

autosomal dominant

only need one copy of mutant allele to have phenotype

29
Q

Risk that a child of either sex will be affected in autosomal dominant inheritance:

A

1/2 (50%)

30
Q

Autosomal dominant disease genotype:

A
  • only need one mutant allele to have phenotype
31
Q

What type of pedigree is this?

A

autosomal recessive

  • parents are unaffected carriers
32
Q

What type of pedigree is this?

A

autosomal dominant

  • every affected individual has an affected parent
  • no skipping of generations
33
Q

Four features of autosomal dominant pedigree:

A
  1. every affected individual has an affected parent; no generation skipping.
  2. males and females equally affected.
  3. about 1/2 of offsprign of affected individual affected.
  4. normal siblings of affected individuals have all normal offspring.
34
Q

In what Mendelian inheritance pattern can male-to-male transmission occur?

A

autosomal dominant

35
Q

Incomplete dominance definition:

A
  • a form of autosomal dominant inheritance
  • individual homozygous for autosomal dominant mutation will be more severely affected than individuals heterozygous for autosomal dominant mutation
  • note: homozygous AD mutations are rare
36
Q

What type of inheritance is this?

(B is mutant allele)

A

incomplete dominance

  • BB more severely affected than Bb
37
Q

Risk that a child of either sex will be affected in incomplete dominance inheritance:

A
  • 3/4 (75%)
  • a form of autosomal dominant inheritance
38
Q

How do you determine whether an X-linked inheritance is dominant or recessive?

A
  • look at phenotype in heterozygous woman
    • no phenotype = recessive
    • phenotype = dominant
39
Q

What type of inheritance is this?

(Green X is mutant allele)

A

X-linked recessive inheritance

(female carrier parent)

  • offspring females 1/2 chance of carrier
  • offspring males 1/2 chance of affected
40
Q

What type of inheritance is this?

(Green X is mutant allele)

A

X-linked recessive inheritance

(affected male parent)

  • all female offspring carriers (obligate)
  • all normal male offspring
41
Q

What type of inheritance has male-to-male transmission?

A
  • autosomal dominant
42
Q

Can X-linked recessive inheritance have male-to-male transmission?

A

NO

43
Q

In X-linked recessive inheritance, what is the one situation where a carrier female will express some phenotype?

A
  • when she has unbalanced X-inactivation
44
Q

What type of pedigree is this?

A

X-linked recessive

  • males exclusively affected*
    • *unless unbalanced X-inactivation in heterozygous female
45
Q

Four features of X-linked recessive inheritance:

A
  1. males exclusively affected*
    • *unless unbalanced X-inactivation in females
  2. Gene transmitted from affected male to all daughters
  3. Mutant allele may be transmitted through a series of carrier females
46
Q

Distinguishing features of X-linked dominant inheritance:

A
  1. trait never passed from father to son
  2. affected father and normal female parents will have:
    • all affected daughters
    • all normal sons
47
Q

What type of pedigree is this?

A

X-linked dominant

  • all daughters of affected male are affected
  • all sons of affected male are normal
48
Q

What types of genotype does phenotype occur in dominant inheritance?

A
  • homozygote and heterozygote
    • homozygotes more severely affected
49
Q

What types of genotype does phenotype occur in recessive inheritance?

A
  • homozygote, hemizygote, compound heterozygote
50
Q

What type of inheritance pattern are males and females equally affected?

A

autosomal dominant and autosomal recessive

51
Q

What type of inheritance pattern are males affected much more than females?

A

X-linked recessive

52
Q

What type of inheritance pattern are females affected more than males?

A

X-linked dominant

53
Q

Reduced penetrance definition:

A
  • when the probability that a mutant gene will have a phenotypic expression is less than 100%
    • “all or none” phenotype
54
Q

Variable expressivity definition:

A
  • when the severity of expression of the phenotype among individuals with the same disease-expressing genotype is different
55
Q

Sex-limited traits definition:

A
  • when autosomal mutations are inherited by both sexes, but the phenotype is only evident in one sex
  • due to anatomical or physiological differences
56
Q

Male-limited precious puberty is a form of what type of inheritance?

A
  • autosomal dominant sex–limited phenotype
    • only boys affected
57
Q

Hemochromatosis is a form of what type of inheritance?

A

autosomal recessive sex-limited trait

  • more common in males
  • a disease caused by excess iron
  • females rid excess iron through pregnancy and menstruation
58
Q

Mosaicism definition:

A
  • the presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg.
    • pure somatic
    • pure germline
59
Q

How to determine germline mosaicism:

A
  • both parents normal and test negative for being carriers; more than one child affected with a highly penetrant AD or XL-R disorder
  • all gametes of one parent are affected
60
Q

Genetic lethal definition:

A
  • diseases that are produced by dominant alleles with effects so severe that persons with them do not have children
61
Q

Seven factors that create exceptions to Mendelian rules:

A
  1. Reduced penetrance
  2. Variable expressivity
  3. Sex-limited traits
  4. Germ-line mosaicism
  5. Genetic Imprintng
  6. New Mutations
  7. Misattributed Paternity
62
Q

Genomic imprinting definition in regard to inheritance:

A
  • when the sex of the transmitting parent plays a role in the expression of the phenotype in affected children
  • “parent of origin” specific pattern is present in all somatic cells, but reversed in germ cells
63
Q

Genetic imprinting (methylation) is reversed in:

A

the gametes

64
Q

Two most common disorders which arise from genetic imprinting affecting pedigrees:

A
  1. prader-willi
  2. angelman syndrome

DELETIONS OCCUR ON SAME REGION OF CHROMOSOME 15

65
Q

Prader-Willi syndrome:

A
  • loss of paternally inherited gene
  • 20 maternally imprinted genes affected
  • excessive weight gain, motor and developmental delays
66
Q

Angelman syndrome:

A
  • loss of maternally inherited gene
  • one paternally imprinted gene is affected
  • severe mental retardation/happy/non-verbal

BMS2.01 Single Gene Inheritance (CORBETT) (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions