Ch.2 Genes and genetic disease Flashcards
1
Q
DNA consists of what three main things?
A
Deoxyribose, phosphate molecule, and four nitrogenous bases
2
Q
Proteins are composed of ____ _____. How many?
A
amino acids; 20
3
Q
What are the two main steps of DNA replication?
A
- Untwisting and unzipping of the DNA strand.
2. Complementary base pairing by DNA polymerase (A-T and C-G)
4
Q
In DNA replication, does the single strand act as a template?
A
Yes
5
Q
in DNA replication, what allows for complementary base pairing?
A
DNA polymerase
6
Q
A ______ is any inherited alteration of genetic material
A
mutation
7
Q
The insertion or deletion of one or more base pairs is which type of mutation?
A
Frameshift
8
Q
Which type of mutation causes a change in the entire reading frame?
A
Frameshift
9
Q
Which type of mutation occurs in the absence of exposure to known mutagens?
A
Spontaneous
10
Q
Areas of chromosomes that have high mutation rates are called?
A
Mutational hot spots
11
Q
What is a mutagen?
A
Agent known to increase the frequency of mutations
12
Q
List some common chemical mutagens
A
Nitrogen mustard, vinyl chloride, alkylating agents, formaldehyde, and sodium nitrate
13
Q
RNA is synthesized from the DNA template. This occurs during _______
A
transcription
14
Q
With transcription, DNA polymerase binds to the promoter site. T or F?
A
False, RNA polymerase binds to promoter site
15
Q
What is the result after RNA is synthesized from the DNA template and RNA polymerase binds to the promoter site?
A
Formation of mRNA
16
Q
after RNA polymerase detaches, where does the mRNA go?
A
It moves out of the nucleus and into the cytoplasm
17
Q
Transcription of mRNA synthesis continues until?
A
Until the termination sequence is reached
18
Q
T or F: introns are removed and the exons are then spliced together before mRNA migrates to the cytoplasm
A
True
19
Q
What is translation?
A
Process by which RNA directs the synthesis of a polypeptide via interaction with tRNA
20
Q
During translation, what is the site of protein synthesis?
A
ribosome
21
Q
_____ is the process by which RNA directs the synthesis of a polypeptide via interaction with tRNA
A
translation
22
Q
tRNA contains a sequence of _______ (anticodon) complementary to the triad of nucleotides on the ____ strand (codon)
A
nucleotides; mRNA
23
Q
The ____ moves along the mRNA sequence to translate the amino acid sequence
A
ribosome
24
Q
Translation continues until….
A
termination sequence is reached
25
After the termination sequence is reached, the polypeptide is released into the ______
cytoplasm
26
T or F, RNA contains the same bases as DNA
False
27
T or F, DNA is replicated in the cytoplasm
False; nucleus
28
T or F, a mutation is an inherited alteration of DNA
True
29
Diploid cells are ______ and haploid cells are _______
somatic; gametes
30
Sperm and egg cells are called
gametes
31
How many chromosomes do gametes contain?
23 (one member of each chromosome pair)
32
How many chromosomes do somatic cells contain?
46 (23 pairs)
33
Mitosis is the formation of ____ cells whereas meiosis is the formation of ______ cells from diploid cells
somatic cells; haploid cells
34
What are autosomes?
The first 22 of the 23 pairs of chromosomes in males and females.
35
T or F, females have a nonhomologous pair of chromosomes XX
False...XX is homologous (same)
36
The ordered display of chromosomes is the _____
karotype
37
____ cells have a multiple of the normal number of chromosomes
Euploid
38
____ and _____ cells are euploid forms
haploid and euploid
39
When is a euploid called a polypoid cell?
When a euploid has more than the diploid number
40
What is a triploidy?
A zygote having three copies of each chromosome (69)
41
What is a tetraploidy?
four copies of each chromosome (92)
42
What is the leading cause of miscarriages and intellectual disability?
Chromosomal aberrations
43
Do triploid or tetraploid fetuses survive?
No
44
What is an aneuploidy?
A somatic cell that does not contain a multiple of 23 chromosomes
45
A ______ is a cell containing three copies of one chromosome
trisomic/trisomy
46
Monosomy is the presence of what?
Presence of only one copy of any chromosome
47
Monosomy is lethal, but infants can survive with trisomy of certain chromosomes. T or F
True; it is better to have extra than less
48
What is the usual cause of aneuploidy?
Nondisjunction
49
What is nondisjunction"?
Failure of the homologous chromosomes or sister chromatids to separate normally during meiosis or mitosis
50
What is a partial trisomy?
When only an extra portion of a chromosome is present in each cell
51
Trisomies occurring only in some cells of the body are called _____ ______
Chromosomal mosaics
52
Trisomy 21 is also known as _____ ______
down syndrome
53
What is the best known example of an aneuploidy?
Down syndrome
54
What is the ratio of Down syndrome to live births?
1:800
55
What are some of the phenotypic traits seen in people with Down syndrome?
Mentally challenged, low nasal bridge, epicentral folds, protruding folds, protruding tongue, low-set ears, poor muscle tone, etc.
56
The risk of birthing an infant with Down syndrome increases with maternal age above
35
57
What is one of the most common sex chromosome aneuploidy?
Trisomy X (three X chromosomes)
58
What are some of the symptoms associated with trisomy X
Sterility, menstrual irregularity, and/or intellectual disability
59
Do symptoms worsen with each additional X with a sex chromosome aneuploidy?
Yes
60
What causes Turner syndrome?
females only having only one X chromosome (as opposed to XX)
61
What are the characteristics of Turner syndrome?
- Underdeveloped ovaries (sterile)
- Short stature (~ 4"7)
- Webbing of the neck
- edema
- un.dev. breasts with wide set nipples
- high number of aborted fetuses
62
With Turner syndrome, the X is usually inherited from the mother or father?
Mother
63
Which syndrome is associated with being mentally challenged and having poor muscle tone?
Down syndrome
64
Which syndrome is associated with underdeveloped ovaries and webbing of the neck?
Turner syndrome
65
Which syndrome is associated with male appearance, small testes, and sparse body hair
Klinefelter syndrome
66
Individuals with at least two X's and one Y chromosome are born with _____ syndrome
Klinefelter
67
Can individuals with Klinefelter syndrome be XXY and XXXY
Yes
68
Do the abnormalities of Klinefelter syndrome increase with each X or each Y?
X
69
What is a clastogen?
A mutanic agent that disrupts or causes chromosomal breakage
70
Examples of clastogens?
Ionizing radiation, chemicals, and viruses
71
What's important about chromosomal breakage?
If a chromosome break does occur, physiologic mechanism will usually repair the break, but breaks can heal in a way that alters the structure of the chromosome
72
What causes Cri du chat syndrome?
Deletion of the short arm of chromosome 5
73
Cri du chat causes..
low birth weight, severe intellectual disability, and microcephaly
74
does duplication of a gene or gene sequence have more or less consequences than deletion of a gene or gene sequence?
Less consequences
75
Duplication in the same region as. Cri du chat causes intellectual deficiencies but fewer what?
Physical abnormalities
76
Inversions (when looking at abnormalities in chromosome structure) are what?
- Two breaks on a chromosome
| - Reversal of the gene order
77
Inversions usually occur from a breakage that gets reversed during reattachment. T or F
True
78
What are translocations?
The interchanging material between non homologous chromosomes
79
Robertsonian translocation occurs when?
When fusion at centromere forms a single chromosome
80
What are fragile sites?
Areas on chromosomes that develop distinctive breaks or gaps when cells are cultured
81
Fragile sites have no apparent relationship to disease except for ___ _ _____
Fragile X syndrome
82
Where do you find fragile x syndrome?
The long arm of the chromosome
83
Which syndrome is second in occurrence to Down syndrome with intellectual disability?
Fragile X syndrome
84
Why is there a higher incidence of Fragile X syndrome in males?
Because they only have one X chromosome
85
1. Principle of segregation
| 2. Principle of independent assortment. These are....
Mendel's law of inheritance
86
T or F: The current understanding of chromosomal behavior is consistent with Mendel's laws--chromosome theory of inheritance
T
87
Pedigrees begin with the _____, the first person who is diagnosed
Proband
88
Autosomal _____ inheritance relatively rarely causes diseases
dominant
89
Is Huntington disease autosomal dominant or recessive?
Dominant
90
The probability that an individual will develop a genetic disease is _____ ____
recurrence risk
91
_______ is the percentage of individuals with a specific genotype who also express the expected phenotype
Penetrance
92
What is incomplete penetrance?
When an individual who has the gene for a disease, but not does not express the disease
93
Which type of tumor (in children) demonstrates incomplete penetrance (90%)
Retinoblastoma
94
T or F, ADPKD has full or nearly so penetrance
True
95
What is the difference between ADPKD and ARPKD concerning the cysts?
Cysts in kidneys develop much earlier than in people with ADPKD
96
Alterations in PKD1 or PDK2 gene occurs with ______
AD-PKD
97
Does AD-PKD have a high recurrence risk?
Yes
98
______: Same DNA sequence can produce different phenotypes. due to chemical modification that alters expression of genes
Epigenetics
99
What is genomic imprinting?
When one parent imprints (aka inactivates) the gene during transmission to offspring
100
With autosomal recessive inheritance, are both parents of affected individuals heterozygous carriers?
Yes
101
Recurrence for offspring is 25%. This is pertaining to autosomal recessive or dominant?
Recessive
102
Is cystic fibrosis ARI or ADI
recessive
103
People with ARPKD have inherited a faulty version of gene ______
PDK1
104
What is the carrier frequency of ARPKD
1:70 to 1:100
105
Mutation in the cystic fibrosis transmembrane conductance regulator ______ gene results in cystic fibrosis
CFTCR
106
Consanguinity is....
mating of two related individuals
107
_______ dramatically increases the recurrence risk of recessive disorders
Consanguinity
108
Why are sex linked disorders usually expressed by males?
Females have another X chromosome to counteract the abnormal gene
109
Most sex-linked traits are X or Y linked?
X linked
110
Is Duchenne muscular dystrophy sex-linked?
Yes
111
Sex is determined by SRY gene on the short or long arm of the Y chromosome?
Short arm
112
What triggers action of genes on other chromosomes?
The SRY gene on the short arm of the Y chromosome
113
Most X-linked disorders are dominant. T or F
False; recessive
114
Do sons or daughters of female carriers have a 50% risk of being affected?
Sons (daughters have xx)
115
Dominant alleles have observable effects. T or F
True
116
What is crucial about gene mapping?
It can identify links between a disease locus and a "marker" locus
117
Variation in traits caused by interaction between/among genetic and environmental factors
Multifactorial trait
118
What is gene therapy?
Experiments to treat genetic diseases.
119
With _____ ____, you replace a mutated gene with a healthy copy of the gene
gene therapy
