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SFM Quiz 2 > Genetic Inheritance > Flashcards

Genetic Inheritance Flashcards

1
Q

This is the term for the first diagnosed person in a pedigree.

A

Proband

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2
Q

In this type of inheritance, only one allele of a gene is needed for expression. The affected offspring only need one affected parent. Unaffected individuals do not transmit the disease (aa). Trait is expected in every generation at 50 percent.

A

Autosomal Dominant

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3
Q

In autosomal dominant inheritance, males and females can transmit trait to both males and females. That’s why the term _________ is used.

A

Autosomal

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4
Q

In this type of inheritance, two copies of a mutant allele (gene) is needed to influence phenotype. Females and males affected equally. Occurrence more likely among individuals who share genes (i.e., first cousins).

A

Autosomal recessive

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5
Q

In autosomal recessive inheritance, if only one mutant allele is present then the individual is a ________ of the mutation but will not display the phenotype.

A

Carrier

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6
Q

In autosomal recessive inheritance, if two carriers procreate then what are the percentage outcomes (punnet square)?

A

25 percent chance unaffected
25 percent chance affected
50 percent chance unaffected carrier

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7
Q

In this type of inheritance, mostly males are affected but females can be too if they are homozygous for the trait. It is always expressed in male carriers. Females can be heterozygous or homozygous.

A

X-linked recessive

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8
Q

Disease allele on X in males is termed…

A

Hemizygous

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9
Q

In X-linked recessive inheritance, female carriers transmit the disease allele to _____ of sons and _____ of daughters. All ________ of affected males are heterozygous carriers.

A

50 percent
50 percent
Daughters

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10
Q

T/F. There can be father-to-son transmission with X-linked inheritance.

A

False. Fathers only pass Y chromosome to sons.

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11
Q

What is an example of an X-linked recessive disease?

A

DMD

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12
Q

What does mtDNA encode for?

A

rRNA
tRNA
13 polypeptides involved in OxPhos

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13
Q

mtDNA undergoes transcription in the mitochondrion, independent of the nucleus. It contains no _______, and is inherited exclusively from the ________.

A

Introns

Mother

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14
Q

T/F. The mutation rate of mtDNA is 10x higher than nDNA.

A

True

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15
Q

Why does mtDNA have a higher mutation rate than nDNA?

A
    • No DNA repair mechanisms

- - Damage from free oxygen radicals from OxPhos

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16
Q

In a pedigree, if the mother is affected and then affects all her offspring, what type of inheritance could that be?

A

Mitochondrial inheritance

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17
Q

This mitochondrial disorder is due to a degeneration of retinal ganglion cells. It is caused by one of three pathogenic mtDNA point mutations affecting NADH dehydrogenase.

A

Leber’s hereditary optic neuropathy (LHON)

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18
Q

LHON is caused by a point mutation affecting which enzyme?

A

NADH dehydrogenase

***Starves RGCs of energy, making them unable to transmit signals to the brain

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19
Q

LHON can cause an acute or subacute loss of…

A

Central vision

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20
Q

This mitochondrial disorder is caused by a mutation in the gene encoding for tRNA for lysine, which disrupts the synthesis of cytochrome-c oxidase.

A

Myoclonic epilepsy and ragged red fibers (MERRF)

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21
Q

Patients with MERRF present with ataxia and seizures, largely affects the muscles and nerves. This is due to a mutation in the synthesis of which enzyme?

A

Cytochrome-c oxidase

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22
Q

This is the most common maternally-inherited mitochondrial disease. It affects many body systems, particularly the brain, nervous system, and muscles. It can cause stroke, dementia, diabetes, deafness, short stature, and infertility.

A

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS)

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23
Q

This is the definition for mitochondrial disorders that vary depending on the number of diseased mitochondria within the cells. There is a specific “threshold” for how many mitochondria must be diseased.

A

Heteroplasmy

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24
Q

This type of inheritance is very rare, and there are no carriers. Males with the disease allele transmit the trait only to their daughters at 100 percent transmission. Females with the allele transmit to both daughters and sons at 50 percent transmission.

A

X-linked dominant

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25
Q

This is the term for cells with a normal number of chromosomes.

A

Euploid

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26
Q

This is the term for cells that contain a complete set of extra chromosomes.

A

Polyploidy

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27
Q

This is the term for cells containing a missing or additional individual chromosome.

A

Aneuploidy (i.e., monosomy, trisomy)

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28
Q

This occurs due to improper cell division during meiosis, causing there to be too many or too few chromosomes in offspring.

A

Nondisjunction

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29
Q

Why does a mother’s age affect the risk of down syndrome in their babies?

A

Women are born with the complete number of eggs they’ll have their whole life. As they age, these cells can mutate or develop abnormalities. So, the older the woman is then the more likely eggs have mutated, causing diseases such as down syndrome.

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30
Q

Mendelian inheritance dictates that we receive an active copy of each gene from each of our parents. However, in _______ ________ certain genes are expressed only from the mother or father.

A

Genomic imprinting

31
Q

Imprinted alleles are silenced such that the gene is expressed only form the non-imprinted allele of the mother or father. Imprinting is an epigenetic process that involves the _________ and ________ modification of egg or sperm cells during their formation while the genetic sequence is unchanged.

A

Methylation (silences gene)

Histone (chromatin condensation - silences gene)

32
Q

Imprinting pattern is duplicated in all somatic cells. Very few genes are imprinted, but dysfunction of these genes leads to genetic defects such as…

A

Prader-Willi syndrome

33
Q

This is a phenomenon when an individual receives two copies of a chromosome or part of a chromosome from one parent and no copies from the other parent.

A

Uniparental disomy (UPD)

34
Q

UPD can occur as random error in meiosis during the formation of egg and sperm cells, or could occur in early fetal development. Often is asymptomatic, however if it occurs in ________ genes then there may be issues.

A

Imprinted

35
Q

Prader-Willi syndrome occurs from UPD, which involves imprinting gene on the long arm of __________. Dysfunction of this gene leads to uncontrolled eating and obesity.

A

Chromosome 15

36
Q

This type of chromosomal mutation occurs when a segment of chromosomal DNA is present in its reverse orientation.

A

Inversion

37
Q

This type of chromosomal mutation occurs when a segment of DNA is lost.

A

Deletion

38
Q

This type of chromosomal mutation occurs when a segment of DNA is copied, resulting in amplification of genes contained in that region.

A

Duplication

39
Q

This type of chromosomal mutation occurs when two different chromosomes exchange segments of their DNA. It can either be balanced (where the resultant hybrid chromosomes are similar to length of normal counterparts) or unbalanced (where they are dissimilar in length).

A

Translocation

40
Q

This type of translocation occurs when there is an exchange of material between non homologous chromosomes.

A

Reciprocal translocation

41
Q

This type of translocation occurs when the long arm of two acrocentric chromosomes combine, and the short arm is lost typically.

A

Robertsonian translocation

42
Q

This is a technique that allows the determination of the number, size, and gross structures of metaphase chromosomes.

A

Karyotyping

43
Q

Karyotyping is the traditional gold standard cytogenic method used in identifying several chromosomal abnormalities associated with genetic disorders, but it does not provide information at the _________ level.

A

Molecular

44
Q

The karyotype for this disease is 45, XO. It is a monosomy, and all are female because there can be no Y. They have short stature, ovarian hypofunction/premature ovarian failure, infertility, and most do not undergo puberty. Some have a webbed neck and CV defects, but no cognitive defects.

A

Turner syndrome

45
Q

This disease is due to a deletion of a region of the paternal chromosome 15. It results in short stature, hypotonia, small hands/feet, obesity, mild to moderate intellectual disability, and uncontrolled eating.

A

Prader-Willi Syndrome

46
Q

This disease is due to a deletion of a region of the maternal chromosome 15. It results in severe intellectual disability, seizures, and ataxic gait.

A

Angelman Syndrome

47
Q

This karyotype for this disease is 47, XXY. There can be varying presentations, as well as varying degrees of cognitive, social, behavioral, and learning difficulties.

A

Klinefelter Syndrome

48
Q

This disease can result in primary hypogonadism (low T), small and/or undescended testes, gynecomastia, infertility, and tall stature.

A

Klinefelter Syndrome

49
Q

T/F. In Klinefelter Syndrome, variability in X numbers (48, XXXY; 49, XXXXY) can increase symptoms.

A

True

50
Q

The karyotype for this disease is 47, XX +21. It is the most common and strongly associated with increased maternal age. Results most commonly from maternal meiotic nondisjunction (in the ovum).

A

Trisomy 21 (Downs Syndrome)

51
Q

Downs syndrome has varying cognitive impairment and structural abnormalities including: increased nuchal translucency, _______ defects, duodenal atresia, ventriculomegaly, absent nasal bone, and short limbs.

A

Cardiac

52
Q

The karyotype for this disease is 47, XX +13. There are severe developmental abnormalities, and most die before birth. Most perinatal deaths within 1 week, and they contain heart abnormalities, kidney malformations, CNS dysfunction, microcephaly, malformed ears, cleft lip/palate, closely spaced/absent eyes, and clenched hands and polydactyl.

A

Trisomy 13 (Patau Syndrome)

53
Q

This is the term for the frequency a gene manifests itself and shows the clinical presentation (phenotype). For example, in some cases 100 percent of individuals inheriting a genetic defect show the clinical presentation.

A

Penetrance

**So there is 100 percent penetrance

54
Q

An example of penetrance is ________, which is autosomal dominant inheritance. Phenotype occurs in 90 percent of individuals inheriting gene defect, so there is 90 percent penetrance.

A

Retinoblastoma

55
Q

This is the term that describes the range of phenotypes that vary between individuals with a specific genotype. An example is Neurofibromatosis, which develops tumor-like growths that are pigmented areas the color of coffee with cream. Spots differ in number, shape, size and position.

A

Variable expressivity

56
Q

This disease exhibits variable expressivity and affects the connective tissue, subsequently many different systems. People have really long arms and digits. Ectopia lentil, and weakened and stretched aorta may lead to an aneurysm and aortic dissection.

A

Marfan syndrome

57
Q

Marfan syndrome is due to a mutation in the gene encoding _______ located on chromosome 15. _______, which is the major component of microfibrils, is found in large amounts in the aorta and other connective tissues.

A

Fibrillin

Fibrillin

58
Q

This is the term for a single disorder, trait or pattern of traits caused by mutations in genes at different chromosomal loci. Only one mutant locus is needed for the phenotype to manifest (i.e., mutations in COL1A1, COL1A2, CRTA, and P3H1).

A

Locus heterogeneity

59
Q

This disease is an example of locus heterogeneity. It is also called Brittle-bone disease and is due to mutations in collagen genes (two loci: chromosome 7 and 17), either mutation exhibits similar phenotypes (varying severity).

A

Osteogenesis Imperfecta

60
Q

This is the term for a number that reflects the chance or likelihood that a particular event will occur. Expressed as a number (0-1) or as a percentage (0-100 percent).

A

Probability

61
Q

In probability, if the occurrence of one does not affect the probability of occurrence of the other then it has…

A

Independence

62
Q

The multiplication rule: The probability of a given outcome in multiple trials is the product of the probabilities of each trial outcome.

The addition rule: The probability of either one outcome or another is the sum of the two probabilities.

A 
Multiplication -- 
What's the prob of producing 3 girls?
1/2 x 1/2 x 1/2 = 1/8
What's the prob of producing 3 boys? 
1/2 x 1/2 x 1/2 = 1/8

Addition –
Prob of producing either 3 girls or 3 boys?
1/8 + 1/8 = 1/4

63
Q

What is the Hardy-Weinberg equation?

A

p(2) + 2pq + q(2) = 1

***remember p+q = 1

64
Q

(GENOTYPE/ALLELE) frequency is the number of individuals with a given genotype divided by the total number of individuals in the population. The three possible genotypes are homozygous dominant (AA), homozygous recessive (aa), and heterozygous (Aa).

A

Genotype

***These are p(2), q(2), and 2pq

65
Q

(GENOTYPE/ALLELE) frequency is the frequency of occurrence or proportions of different allele of a particular gene in a given population. Two possible alleles are dominant (A) and recessive (a).

A

Allele

***These are p (dominant) and q (recessive)

66
Q

What does (p) and (q) equal in the Hardy-Weinberg?

A 
p = frequency of dominant allele (i.e., A) 
q = frequency of recessive allele (i.e., a)

***remember have to double allele population (because each person has 2)

67
Q

In this inheritance pattern, there can be vertical transmission of the disease phenotype. There is a lack of skipped generations, and there are roughly equal numbers of affected males and females. Father-to-son transmission may be observed.

A

Autosomal dominant

68
Q

In this inheritance pattern, there is clustering of the disease phenotype among siblings. The disease is not usually seen among parents or other ancestors. Equal number of affected males and females. Consanguinity may be present (mating between relatives).

A

Autosomal recessive

69
Q

_________ mating’s are more likely to produce offspring affected by rare autosomal recessive disorders. Studies show that mortality rates among the offspring of first-cousin mating’s are up to 9 percent higher than the general population.

A

Consanguineous

70
Q

This is the term for trains in which variations are though to be caused by the combined effects of multiple genes.

A

Polygenic

71
Q

This is when environmental factors cause variation in the trait.

A

Multifactorial

72
Q

For diseases that do not follow the bell-curve (distribution in populations) there is an underlying liability distribution. For multifactorial diseases that are either present or absent, it is thought that a ________ of liability must be crossed before the disease is expressed. Below this, then the person appears normal. Above this then the person is affected by the disease.

A

Threshold

73
Q

In multifactorial inheritance, the least affected sex has a (HIGHER/LOWER) risk threshold and transmits the condition more often to the most frequently affected sex.

A

Higher

***i.e., Children of women with pyloric stenosis are more likely to be born with condition (especially males)

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

74
Q

This is due to muscular hypertrophy between stomach and duodenum. It leads to vomiting and obstruction, and is five times more common in males than females. Males need less risk genes to show disease, while females need more risk genes (multifactorial inheritance).

A

Pyloric stenosis

SFM Quiz 2 (12 decks)

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