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Clinical Science > Genetics intro > Flashcards

Genetics intro Flashcards

1
Q

Who was the Australian monk and founder of modern genetics?

A

Gregor Mendel

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2
Q

Before Gregor Mendel, how did scientists think traits were inherited?

A

by blending of parents’ traits

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3
Q

What were the results of the DNA analysis on Gregor Mendel when his body was exhumed?

A

-very large brain
-neurologic disease genes identified

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4
Q

What did Gregor Mendel experiment with?

A

pea plants

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5
Q

What are the names of Mendel’s Laws?

A
  1. law of segregation
  2. law of independent assortment
  3. law of dominance
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6
Q

What is the law of segregation?

A

each person has two alleles for each gene and only one is contributed to a gamete in a random manner with equal frequency

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7
Q

What is the law of independent assortment?

A

alleles for different genes are sorted into gametes independently of each other, therefor one allele of a gene does not affect a different allele of a different gene

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8
Q

What is the law of dominance?

A

in a heterozygote, one trait will conceal the other and the presence of a dominant allele will conceal the trait of the recessive allele

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9
Q

What is it called when alleles of a gene are identical (AA or aa)?

A

homozygous

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10
Q

What is it called when alleles of a gene are different (Aa)?

A

heterozygous

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11
Q

What is the location of a gene on a chromosome called?

A

locus

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12
Q

What is the individuals collection of genes, or can reference to two alleles that code for a gene (AA, Aa, aa)?

A

genotype

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13
Q

What is the observable trait or set of traits that is created from your genetic makeup–hair color, flower color, wrinkled seeds?

A

phenotype

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14
Q

Genotype determines ___________

A

phenotype

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15
Q

What is is called when a disease is expressed in 100% of people with a particular genotype, incomplete or complete?

A

penetrance

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16
Q

most diseases are _______

A

polygenic

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17
Q

What does it mean when it is said that most diseases are polygenic?

A

several or many alleles of several genes are interacting

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18
Q

How many chromosomes do humans have?

A

46 chromosomes
-22 pairs of autosomes
-1 par of sex chromosomes

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19
Q

During cell division, what can lead to an abnormal number of chromosomes?

A

nondisjunction

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20
Q

What is nondisjuction?

A

failure of chromosome pairs to separate

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21
Q

What are examples of nondisjunction that occurs during cell division?

A

monosomy
trisomy
polysomy

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22
Q

What is it called when only one member of chromosome pair is present?

A

monosomy

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23
Q

What is it called when three chromosomes are present?

A

trisomy

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24
Q

What is it called when one chromosome is present 4 or more times?

A

polysomy

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25
Q

What can occur in a chromosomal region that can cause no or severe changes in a phenotype?

A

deletions and inversions

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26
Q

What is the most common trisomy?

A

down syndrome (trisomy 21)

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27
Q

The risk of having a child with down syndrome increases with _______

A

maternal age

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28
Q

Women who become pregnant at 35 or older are considered high-risk for what?

A

down syndrome and other malformations due to increased age

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29
Q

What tests are beneficial for diagnosis of down syndrome during pregnancy?

A

labs and ultrasounds

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30
Q

What are these facial characteristics associated with?
-flat facial features
-upward slant of eyes
-brushfield spots on iris of eyes
-changes to ear structure
-small nose
-enlarged and protruding tongue

A

down syndrome

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31
Q

These abnormalities can be present in individuals with what?
-deep palmar crease (simian crease)
-extra space between first and second toe
-hyper flexibility of joints
-decreased muscle tone (hypotonia)

A

Down syndrome

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32
Q

What are the organ manifestations of down syndrome?

A

*cardiac defects:
-most common cause of mortality in DS
-atrioventricular septal defects
*gastrointestinal malformations
*vision and hearing loss
*pulmonary infections

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33
Q

What are the growth feature manifestations of Down syndrome?

A

*short stature
*short fingers

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34
Q

What are the neuropsychiatric manifestations associated with down syndrome?

A

*behavioral issues:
-issues managing compulsive behaviors and dealing with frustration
*increased risk of Alzheimer’s beginning as early as fifth decade of like (40s):
-affects 40-80% of DS patients
-manifests with early onset of memory loss, then progresses

35
Q

What occurs in Klinefelter syndrome?

A

the ovum with XX is fertilized by a sperm with a Y leading to an XXY genotype

36
Q

Klinefelter syndrome is the most common genetic abnormality that causes what?

A

primary hypogonadism and infertility

37
Q

What is hypogonadism?

A

testicular development is not normal for where it should be leading to small testes

38
Q

In Klinefelter syndrome, infertility is often due to what?

A

impaired spermatogenesis

39
Q

What percentage of those born with Klinefelter syndrome will develop feminine appearing breasts?

A

50%

40
Q

Affected individuals with Klinefelter syndrome may have?

A

*impaired psychosocial skills:
-ADHD, impaired judgement, and impaired insight
*impaired higher language skills
*increased risk of:
-Non-Hodgkin’s Lymphoma
-ulcers of the legs
-diabetes
-lupus

41
Q

Affected individuals with Klinefelter syndrome will have?

A

*decreased serum testosterone resulting in:
-small testes
-abnormally low sperm count
-abnormal arm and leg length (tall stature)
*increased risk of breast cancer and pulmonary disease

42
Q

What occurs in Turner syndrome?

A

ovum that lacks X fertilized by sperm with X or normal ovum (X) fertilized by sperm lacking X or Y, representing a genotype as XO

43
Q

Those with turner syndrome will have what type of mental development?

A

normal mental development

44
Q

What is the female appearance of individuals with Turner syndrome?

A

-short stature
-prominent neck skin folds
-wide chest with small breasts
-widely spaced nipples
-ovarian dysgenesis leading to low estrogen and often resulting in infertility with primary amenorrhea

45
Q

What is amenorrhea?

A

abnormal menstrual cycle

46
Q

Those with Turner syndrome have an increased risk of what?

A

cardiac disease

47
Q

Why do individuals with Turner syndrome have an increased risk of cardiac disease?

A

they are more likely to have:
-diabetes
-hyperlipidemia
-hypertension
-cardiac structural abnormalities
-aortic dissection

48
Q

Besides the increased risk of cardiac disease, what other consequences are associated with Turner syndrome?

A

-hearing loss
-thyroid disease
-osteoporosis and fracture
-renal structure and abnormalities
-vision/ocular abnormalities
-autoimmune disease

49
Q

What can taking a family history provide?

A

clues to genetic diseases within your patient’s family

50
Q

How many generations should you examine when taking a family history?

A

all first-degree relatives and parents/offspring–3 generations

51
Q

What information should you gather when taking a family history?

A

-age
-sex
-general health
-major illness/disease processes
-cause of death (if applicable)

52
Q

Describe autosomal inheritance

A

-inheritance of an allele from one of the 22 pairs of autosomes
-can be either homozygous or heterozygous
-heterozygous may be termed a “carrier” for the disease

53
Q

In autosomal inheritance, males and females are what?

A

equally likely to inherit the variant gene

54
Q

What are the characteristics of autosomal dominant inheritance?

A

-mutation is a single allele of autosome is enough to cause an altered phenotype or disease
-takes only one affected parent for a child to be affected
-males and females equally affected
-multiple generations are affected causing a vertical pattern (seen in every generation)

55
Q

What are the characteristics of autosomal recessive inheritance?

A

-two copies of an autosome must contain the variant/mutation for disease to occur
-both parents must carry the variant for the disease to manifest in the offspring
-affects males and females equally
-may skip generations, causing a horizontal pattern (skipping generations)

56
Q

Describe x-linked inheritance?

A

-transmitted via x chromosome
-risk of developing disease related to a mutant X-chromosome gene differs between the sexes
**males are hemizygous (XY) for variant allele
**females can be heterozygous (1 copy) or homozygous (2 copies)

57
Q

Why are males more likely to develop the mutated phenotype in X-linked diseases?

A

they only have one X so only one copy of the gene is needed

58
Q

In X-linked dominant diseases, how many copies of the variant X allele is needed to express the phenotype/condition?

A

just one

59
Q

Can a father pass an X-linked dominant disease to his son?

A

no, he only inherits the Y from his dad

60
Q

An affected father of an X-linked dominant disease only passes the disease to who?

A

his daughters (who will be affected)

61
Q

An affected mother of an X-linked dominant disease passes the disease to who?

A

both the males and the females

62
Q

In X-linked dominant diseases, who is affected in every generation?

A

both males and females in each generation because only one variant of X is needed

63
Q

In X-linked dominant diseases, who is more severely affected?

A

males are more severely affected than women and can be lethal in males depending on the allele

64
Q

X-linked recessive diseases are more common in what gender?

A

males

65
Q

Why are X-linked recessive diseases more common in males than females?

A

the presence of an X mutant in a male has no other X to mask its effect because their genotype of XY, whereas females can have an non-affected X than masks the affect of the variant X since their genotype is XX

66
Q

An affected mother with an X-linked recessive disease will have what percentage of affected sons?

A

100% since they get their X from their mother

67
Q

An affected father with an x-linked recessive disease will have how many affected sons?

A

none since the sons get an Y from their father

68
Q

What has their own DNA which encodes tRNA, rRNA, and other proteins?

A

mitochondria

69
Q

Why is the transmission of mitochondrial DNA maternal?

A

sperm does not contribute much to cytoplasm of the zygote

70
Q

In mitochondrial inheritance patterns, the condition is only transmitted via ____________?

A

maternal lines

71
Q

Do affected males of mitochondrial inherited diseases pass the mitochondrial DNA/genes to their offspring?

A

no

72
Q

Who does the mother with a mitochondrial inherited condition pass the condition to?

A

all of her children, both male and female

73
Q

Most of the conditions seen in practice result from what?

A

multifactorial inheritance

74
Q

What is it when genetics plus environment factors or epigenetic changes contribute to a disease, but not all who have the gene develop the disease?

A

multifactorial inheritance

75
Q

What are some diseases associated with multifactorial inheritance?

A

-asthma
-diabetes
-hypertension
-coronary artery disease
-schizophrenia

76
Q

What is the typical inheritance of genetic imprinting?

A

the child receives one allele from each parent

77
Q

What type of inheritance is it when one allele is “silenced” during gamete formation and only when remains functional?

A

genomic imprinting

78
Q

What occurs when methyl groups are attached to the DNA sequences during formation of the egg or sperm and methylation represses the expression of that allele while the other remains unchanged?

A

genomic imprinting

79
Q

Genomic imprinting affected what gender(s)?

A

both male and female, but no mechanism is clear

80
Q

What are some examples of genomic imprinting?

A

-Angelman Syndrome
-Prader-Willi Syndrome

81
Q

What condition occurs when the paternal copy of a gene is imprinted (inactivated) and only the maternal allele is active and there is a variant within the maternal allele?

A

Angelman Syndrome

82
Q

What condition develops when the maternal copy of a gene is imprinted (inactivated) and only the paternal copy is active and there is a variant within the paternal allele?

A

Prader-Willi Syndrome

83
Q

What do both Angelman syndrome and Prader-Willi syndrome result in?

A

neurodevelopment disorders

Clinical Science (18 decks)

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