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Pathophysiology > Genes and Genetic Diseases > Flashcards

Genes and Genetic Diseases Flashcards

1
Q

Genetics is the study of

A

biologic inheritance

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2
Q

the substance that gives the nucleus a granular appearance

A

chromatin

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3
Q

chromatin is observable in ___________ cells

A

non dividing

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4
Q

just before the cell divides, the chromatin condenses to form discrete, dark-staining organelles, which are called

A

chromosomes

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5
Q

With the rediscovery of Mendel’s important breeding experiments at the turn of the twentieth century, it soon became apparent that the chromosomes contained _____, the basic units of inheritance

A

genes

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6
Q

The primary constituent of chromatin is

A

deoxyribonucleic acid (DNA)

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7
Q

Genes are composed of

A

sequences of DNA

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8
Q

By serving as the blueprints of proteins in the body, genes ultimately

A

influence all aspects of body structure and function

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9
Q

Estimates suggest that there are approximately ____________ genes.

A

20,000 to 25,000

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10
Q

An error in one of these genes often leads to

A

a recognizable genetic disease

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11
Q

To date, more than _____ genetic traits and diseases have be identified and cataloged.

A

20,000

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12
Q

As infectious diseases continue to be more effectively controlled, the proportion of beds in pediatric hospitals occupied by children with genetic diseases has

A

risen

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13
Q

many common diseases that primarily affect adults, such as hypertension, coronary heart disease, diabetes, and cancer, are now known to

A

have important genetic components

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14
Q

“gene therapy” is

A

the utilization of normal genes to correct genetic disease

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15
Q

each cell nucleus contains an identical __________ __ ___________

A

complement of chromosomes

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16
Q

DNA is a double _____

A

helix

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17
Q

DNA is made up of these 3 basic components

A

five-carbon monosaccharide deoxyribose(sugar); a phosphate molecule; and four types of nitrogenous bases

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18
Q

Two of the bases, ________ and _______ are single carbon-nitrogen rings called ___________

A

cytosine and thymine

PYRIMIDINES

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19
Q

The other two double carbon-nitrogen ring bases are called _______. Their names are _______ and _______.

A

PURINES

adenine and guanine

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20
Q

the four bases are commonly represented by their first letter —-

A

ACTG

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21
Q

the sides of the dna ladder consist of

A

deoxyribose and phosphate molecules (united by strong phosphodiester bonds)

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22
Q

the rungs of the ladder are formed from

A

the nitrogenous bases

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23
Q

the base (rung) projecting from one side is bound to the base projecting from the other by a weak ________ bond

A

hydrogen

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24
Q

which nitrogenous bases pair with eachother?

A

adenine—thymine

guanine—cytosine

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25
Q

Each DNA subunit—consisting of one deoxyribose molecule, one phosphate group, and one base—is called

A

a nucleotide

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26
Q

dna directs the synthesis of all the body’s

A

proteins

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27
Q

proteins are composed of one or more

A

polypeptides (intermediate protein compounds)

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28
Q

polypeptides in turn consist of

A

sequences of amino acids

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29
Q

the body contains __ different types of amino acids. they are specified by the _ ___________ _____

A

20

4 nitrogenous bases

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30
Q

To specify (code for) 20 different amino acids with only 4 bases, different combinations of bases, occurring in groups of 3, are used. These triplets of bases are known as

A

codons

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31
Q

the genetic code is ‘universal’. what does this mean?

A

ALL living organisms use precisely the same DNA codes to specify proteins EXCEPT FOR MITOCHONDRIA - the cytoplasmic organelles in which cellular respiration takes place - they have their own extra nuclear DNA

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32
Q

each side of the DNA molecule consists of alternating

A

sugar and phosphate groups

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33
Q

the sequence of these nitrogenous pairs constitutes a genetic code that determines

A

the structure and function of a cell

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34
Q

The consistent pairing of adenine with thymine and of guanine with cytosine is known as _____________ ____ _______ and is the key to ________ ___________

A

complementary base pairing

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35
Q

a mutation is

A

any inherited alteration of genetic material

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36
Q

when one base pair replaces another, this type of mutation is called a

A

base pair substitution

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37
Q

base pair mutations may cause _______ or be ______ substitutions that do not change amino acids.

A

disease or be subtle

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38
Q

base pair mutations that DO NOT CHANGE THE AMINO ACID SEQUENCE and HAVE NO CONSEQUENCE are called

A

silent mutations

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39
Q

base pair mutations that do alter amino acids consist of two basic types:

A

missense and nonsense mutations

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40
Q

missense mutations produce a change in

A

a single amino acid

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41
Q

nonsense mutations produce

A

a stop codon in the messenger RNA (mRNA)

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42
Q

frameshift mutations result from

A

the ADDITION or DELETION of a number of bases THAT IS NOT A MULTIPLE OF THREE

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43
Q

a frameshift mutation alters

A

all of the codons downstream from the site of insertion of deletion

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44
Q

how many base pairs in a codon?

A

3

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45
Q

why are frameshift mutations called so?

A

they change the entire “reading frame”

46
Q

why do “in-frame” insertions or deletions tend to have less severe disease consequences?

A

a multiple of three bases is inserted or lost

47
Q

what are mutagens?

A

they are agents increase the frequency of mutations

radiation, mustard gas, formaldehyde etc

48
Q

mutations are rare events. The rate of spontaneous mutations in humans is

A

10^-4 to 10^-7 per gene per generation

49
Q

dna sequences that have particularly high mutation rates are called

A

mutational hot spots

50
Q

DNA is formed and replicated in the

A

cell nucleus

51
Q

protein synthesis takes place in the

A

ribosome

52
Q

DNA code is transported from

A

nucleus to cytoplasm

53
Q

protein is formed through two basic processes:

A

transcription and translation

54
Q

transcription and translation are mediated by

A

ribonucleic acid (RNA)

55
Q

a karyotype or karyogram is

A

an ordered display of chromosomes

56
Q

A cell that does not contain a multiple of 23 chromosomes is

A

an aneuploid cell

57
Q

Aneuploidy is usually the result of

A

nondisjunction

58
Q

among live births, how many have a form of sex chromosome aneuploidy

A

about 1 in 500 males and 1 in 900 females

59
Q

trisomy x effects

A

1 in 1000 newborn females

60
Q

describe trisomy x

A

no overt physical abnormalities, although sterility, menstrual irregularity, or mental retardation is sometimes seen

61
Q

in general, the more x chromosomes a female has the more

A

retardation tends to be present, along with various physical defects in those with 5 or more

62
Q

sterile means

A

not able to produce children

63
Q

Genetic diseases caused by single genes usually follow

A

autosomal dominant, autosomal recessive, or X-linked recessive modes of inheritance.

64
Q

Pedigree charts are important tools in the

A

analysis of modes of inheritance

65
Q

Recurrence risks specify

A

the probability that future offspring will inherit a genetic disease.

66
Q

For single-gene diseases, recurrence risks remain

A

the same for each offspring, regardless of the number of affected or unaffected offspring.

67
Q

The recurrence risk for autosomal dominant diseases is usually

A

50%

68
Q

Germline mosaicism can alter recurrence risks for genetic diseases because

A

unaffected parents can produce multiple affected offspring

69
Q

This situation in germline mosaicism occurs because

A

the germline of one parent is affected by a mutation but the parent’s somatic cells are unaffected.

70
Q

Skipped generations are not seen in

A

classic autosomal dominant pedigrees

71
Q

Males and females are equally likely to exhibit _________ _______ _______ and to pass them on to their offspring

A

autosomal dominant diseases.

72
Q

Many genetic diseases have a _______ age of onset.

A

delayed

73
Q

A gene that is not always expressed phenotypically is said to have

A

incomplete penetrance

74
Q

incomplete penetrance means

A

A gene that is not always expressed phenotypically is said to have

75
Q

Variable expressivity is

A

a characteristic of many genetic diseases

76
Q

Genomic imprinting, which is associated with ________, results in

______________________________________________________________________

A

methylation

differing expression of a disease gene, depending on which parent transmitted the gene.

77
Q

Epigenetics involves changes, such as

A

the METHYLATION of DNA bases, that do not alter the DNA sequence but can ALTER THE EXPRESSION OF GENES

78
Q

Most commonly, parents of children with autosomal recessive diseases are

A

BOTH HETEROZYGOUS CARRIERS of the disease gene.

79
Q

The recurrence risk for autosomal recessive diseases is

A

25%

80
Q

When it comes to autosomal recessive diseases, males and females are

A

equally likely to be affected

81
Q

Consanguinity is sometimes present in

A

families with autosomal recessive diseases

82
Q

Consanguinity also becomes more prevalent with

A

rarer recessive diseases

83
Q

Carrier detection tests for an increasing number of _________ _________ ________ are available.

A

autosomal recessive diseases

84
Q

The frequency of genetic diseases approximately _______ in the offspring of first-cousin matings

A

DOUBLES

85
Q

In each normal female somatic cell, one of the two X chromosomes is

A

inactivated early in embryogenesis

86
Q

X inactivation is

A

random, fixed, and incomplete

87
Q

X inactivation also may involve

A

METHYLATION

88
Q

Gender is determined embryonically by the presence of

A

the SRY gene on the Y chromosome

89
Q

Embryos that have a Y chromosome (and thus the SRY gene) become

A

males

90
Q

Embryos that lack the Y chromosome become

A

females

91
Q

When the Y chromosome lacks the SRY gene

A

an XY female can be produced

92
Q

an X chromosome that contains the SRY gene can produce

A

an XX male

93
Q

X-linked genes are those that are located on the

A

X chromosome

94
Q

Nearly all known X-linked diseases are caused by

A

X-linked recessive genes

95
Q

Males are __________ for genes on the X chromosome

A

hemizygous

96
Q

X-linked recessive diseases are seen much more often in which sex? And why?

A

Males because they need only one copy of the gene to express the disease.

97
Q

Fathers cannot pass ________ genes to their sons

A

X-linked

98
Q

Skipped generations often are seen in X-linked recessive disease pedigrees because

A

the gene can be transmitted through carrier females

99
Q

Recurrence risks for X-linked recessive diseases depend on

A

the carrier and affected status of the mother and father

100
Q

A sex-limited trait is one that

A

occurs only in one sex (gender).

101
Q

A sex-influenced trait is one that occurs

A

more often in one sex than in the other.

102
Q

A marker locus, when closely linked to a disease-gene locus, can be used to

A

predict whether an individual will develop a genetic disease

103
Q

A more complete gene map will facilitate

A

marker studies, gene cloning, studies of gene function and interaction, and gene therapy.

104
Q

Traits that result from the combined effects of several loci are

A

polygenic

105
Q

Multifactoral means

A

When environmental factors also influence the trait

106
Q

Many multifactorial traits have a __________ __ _________ that once its crossed has been crossed, the disease may be expressed.

A

threshold of liability

107
Q

What is used to estimate recurrence risks for multifactorial diseases?

A

Empirical risks - based on direct observation of large numbers of families

108
Q

Recurrence risks for multifactorial diseases become higher if

A

more than one family member is affected or if the expression of the disease in the proband is more severe.

109
Q

Recurrence risks for multifactorial diseases ________ _______ for more remote relatives.

A

decrease rapidly

110
Q

The frequency of recombinations can be used to

A

infer the map distance between loci on the same chromosome

111
Q

During meiosis I, _________ occurs and can cause ____________________________________________________

A

crossover

recombinations of alleles located on the same chromosome.

Pathophysiology (4 decks)

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