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MCM Final > Principles Of Genetic Inheritance > Flashcards

Principles Of Genetic Inheritance Flashcards

1
Q

Each gene occupies a specific place, or _______

A

Locus

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2
Q

___________ = one of two identical copies of a chromosome

A

Chromatid

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3
Q

____________ = connects identical sister chromatids

A

Centromere

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4
Q

_____________ = region at the end of chromosome for stability

A

Telomere

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5
Q

Typical human diploid cell has 23 pairs of chromosomes. 22 pairs are called _______, the 23rd pair is _____ or _____

A

Autosomes

XX or XY

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6
Q

Human ________cells are diploid and differentiated

A

Somatic

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7
Q

________are haploid cells

A

Gametes

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8
Q

______ Cells are undifferentiated and can divide into 2 diploid cells

A

Stem

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9
Q

___________ chromosomes refer to pairs of chromosomes, thus there are 2 copies of each gene with the order of the 4 loci being identical

A

Homologous

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10
Q

Entire set of patient’s chromosomes represents their ___________

A

Karyotype

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11
Q

46 chromosomes in a karyotype are in each of the patient’s diploid cells, unless ___________ occurs, which is a condition in which patients have different genotypes

A

Mosaicism

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12
Q

For Chr16p12.2 -

Identify chromosome, region, band, sub-band, and arm

A 
Chr = 16
Region = 1
Band = 2
Sub-band = 0.2
Arm = p arm
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13
Q

What is a natural form of mosaicism?

A

Lyonization - or X-inactivation. The choice of which X chromosome will be inactivated is random

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14
Q

What is the genotype of Downs syndrome?

A

Some 46XX, some 47XX + 21

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15
Q

What is the genotype of Klinefelter syndrome?

A

Some 46XY; some 47XXY

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16
Q

What is the genotype for Turner syndrome?

A

Some 46XX, some 45XO

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17
Q

Meiosis reduces the total number of chromosomes by half, producing four gametes. In meiosis, __________ ________ produces new combinations of genes

A

Homologous recombination

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18
Q

______________ is the failure of one or more pairs of homologous chromosomes, or sister chromatids, to separate normally during division.

What does this cause?

A

Non-disjunction

Causes spontaneous abortion and mental retardation

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19
Q

How does meiotic cell division produce haploid cells?

A

One round of DNA replication + 2 rounds nuclear divisions

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20
Q

____________ are chromosomes common in both genders (one from each parent)

A

Autosomes

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21
Q

In what 2 ways does meiosis generate genetic diversity?

A

Random segregation of homologs

Crossing over

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22
Q

____________ refers to cells with an abnormal chromosome number

A

Aneuploid

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23
Q

What is the most common cause of mental retardation?

A

Trisomy 21 (Downs)

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24
Q

In 90% of trisomy 21 patients, the addition chromosome is ____________

70% occurs during __________
30% occurs during __________

A

Maternal

1
2

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25
Q

__________ refers to cells with the normal number of chromosomes

A

Euploid

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26
Q

What type of Trisomy 21 is characterized by the genotype 47, XX + 21?

A

Translocation type - due to Robertsonian translocation

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27
Q

What is the Robertsonian Translocation?

A

Long q arm 21 fuses to long q arm 14, resulting in acrocentric chromosomes

28
Q

What type of Trisomy 21 has the genotype 46, XX, der(14;21)(q10; q10), +21?

A

Mosaic type

29
Q

What is the result of methylation on genes?

A

Downregulation

30
Q

Methylated genes are considered to be __________, which can be passed on from generation to generation

A

Imprinted

31
Q

What is the result of two chromosomes from the same parent that have parent-specific imprinting?

A

No gene product

32
Q

Two different conditions occur with the exact same deletion on chromosome 15.

What condition does the child develop if the paternal chromosome is deleted?

A

Prader Willi syndrome

33
Q

Two different conditions occur with the exact same deletion on chromosome 15.

What condition does the child develop if the maternal chromosome is deleted?

A

Angelman syndrome

34
Q

Gregor Mendel is the ‘father of modern genetics’. What 3 laws did he come up with?

A

Genes are discrete units

Law of segregation

Law of independent assortment

35
Q

What are the 2 broad types of genetic diseases?

A

Monogenic (single-gene)

Multifactorial

36
Q

Dystrophin –> Duchenne Muscular Dystrophy

What is the genetic mechanism?

A

Loss of function

37
Q

Oncogene –> cancer

What is the genetic mechanism?

A

Gain of function

38
Q

B-globin –> sickle cell anemia

What is the genetic mechanism?

A

Protein alteration

39
Q

Individuals with distinct genotypes can have a single phenotype, as is the case with ________ _________

Conversely, individuals with the same genotype can have multiple phenotypes, as is the case with _________

A

Cystic fibrosis

PKU

40
Q

Why is it that PKU patients with the same genotype (PAH deficiency) have multiple phenotypes?

A

Some patients will be able to metabolize and excrete Phe more efficiently than others

41
Q

Why is it that cystic fibrosis patients have distinct genotypes and only one phenotype?

A

Whether you have no CFTR proteins at all, or dysfunction of your existing CFTR proteins, you will have the same resulting symptoms

42
Q

When looking at pedigrees, the ________ refers to the first diagnosed person in the pedigree.

A

Proband

43
Q

What type of inheritance is characterized by only 1 allele needed for expression, so only one parent was affected

A

Autosomal dominant inheritance

44
Q

With autosomal dominant inheritance, unaffected individuals do not transmit the trait.

Males and females can transmit the trait to both males and females - (_______________)

Trait is expected in ________ generation

Recurrent risk is ________%

A

Autosomal

Every

50

45
Q

Postaxial polydactyly is an example of what type of inherited disorder?

A

Autosomal dominant

46
Q

What type of inheritance requires 2 copies of a gene to influence the phenotype?

A

Autosomal recessive

47
Q

Tyrosinase-negative albinism is an example of what type of inherited disorder?

A

Autosomal recessive

48
Q

What is the recurrent risk of autosomal recessive diseases?

A

25%

49
Q

With autosomal recessive disease, occurence is more likely among individuals who engage in ___________ mating

A

Consanguinous

50
Q

X-linked Recessive disorders:

Disease allele on X in males is termed ___________

Females can be __________ or ______________

Unaffected males do not transmit the trait

Females transmit to ____% of sons and _____% of daughters

A

Hemizygous

Heterozygous; homozygous

50; 50

51
Q

If a male is a carrier of an x-linked recessive disorder, how many of his potential daughters will be heterozygous carriers?

A

All of them

52
Q

Duchenne muscular dystrophy is an example of what type of inherited disorder?

A

X-linked recessive

53
Q

Hypophosphatemia is what type of inherited disorder?

A

X-linked dominant

54
Q

How do males and females compare in their ability to pass on an x-linked dominant trait?

A

Males with disease allele transmit the trait only to females with 100% transmission rate

Females with disease allele transmit the trait to both male and female offspring with 50% transmission rate

55
Q

The frequency that a gene manifests itself is called _________

A

Penetrance

[with retinoblastoma, the phenotype occurs in 90% of individuals inheriting the gene defect, so 90% penetrance]

56
Q

What type of inheritance is demonstrated by retinoblastoma?

A

Autosomal dominant

57
Q

What is the term used to describe a range of phenotypes that vary between individuals with a specific genotype?

A

Variable expressivity

58
Q

What is a disease example of variable expressivity?

A

Neurofibromatosis

People develop tumor like growths called neurofibromas - cafe-au-lait spots = pigmented areas that vary in their clinical presentation

59
Q

Osteogenesis imperfecta may result from a mutation in either Chr 7 or Chr 17, this is an example of what concept of mendelian inheritance

A

Locus heterogeneity - a single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci

60
Q

What principle specifies the relationship between gene frequencies and genotype frequencies?

A

Hardy-Weinberg principle

61
Q

What type of inheritance is characterized by vertical transmission of phenotype, lack of skipped generations, roughly equal males and females affected, and father-son transmission may occur?

A

Autosomal dominant

62
Q

What type of inheritance is characterized by clustering of disease phenotype among siblings, but not usually seen among parents or other ancestors, equal males and females affected, consanguinity may be present

A

Autosomal recessive

63
Q

Traits in which variation is thought to be caused by the combined effects of multiple genes = _________

A

Polygenic

64
Q

When environmental factors cause variation in the trait, the term __________ is used

A

Multifactorial

65
Q

For diseases that do not follow the bell-curve distribution, there is an underlying ___________distribution. For multifactorial diseases that are either present or absent, it is thought that a ________________ must be crossed before the disease is expressed. Below that, the person appears normal.

A

Liability

Threshold of liability

66
Q

Explain the concept of the threshold model as it relates to pyloric stenosis, which is 5x more common in males than females

A

Children of women with pyloric stenosis are more likely to be born with the condition - especially males

Children of affected males with pyloric stenosis are less likely to be born with the condition

67
Q

The recurrence risk is ______ if more than one family member is affected

If the expression of disease in proband is more severe, the recurrence risk is ________

The recurrence risk is ______ if the proband is of the less commonly affected sex

The recurrence risk is usually _____ in more remotely related areas

A

Higher
Higher
Higher
Decreased

MCM Final (14 decks)

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