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