Human Genetic Diseases Flashcards
1
Q
What is nondisjunction?
A
When chromosomes don’t break away like they are supposed to.
2
Q
What is aneuploidy?
A
The occurrence of one or more extra or missing chromosomes leading to an unbalanced chromosome complement. The most common type of chromosomal abnormality. Most people with aneuploidy have trisomy (three copies of a chromosome) instead of monosomy (single copy of a chromosome). aneuploid cells have an abnormal number of chromosomes.
3
Q
What are trisomies?
A
3 copies of chromosomes. Downs syndrome.
4
Q
What are monosomies?
A
Turner syndrome.
5
Q
What are translocations?
A
A chromosomal abnormality where part or all of a chromosome is transferred to another non-homologous chromosome. There are three types of translocation: balanced, robertsonian, and reciprocal.
6
Q
What are deletions?
A
A genetic change that involves the absence of a segment of DNA. DiGeorge syndrome is a disorder caused due to the deletion of a small segment of chromosome 22.
7
Q
What are duplications?
A
a mutation where one or more copies of a DNA segment is produced and duplicated. A certain chromosome can duplicate causing too much of one protein.
8
Q
Explain reciprocal translocation vs. robertsonian translocation?
A
In a reciprocal translocation, two different chromosomes have exchanged segments with each other. In a Robertsonian translocation, an entire chromosome attaches to another at the centromere.
9
Q
How do pedigree analysis work with DNA genetics?
A
It’s a way we can see how things are passed down through families.
10
Q
Define autosomal Dominant inheritance
A
– these traits are inherited equally in males and females and do not skip generations.
11
Q
Define autosomal recessive
A
these traits are inherited equally in males and females and can skip generations.
12
Q
Define x-lined dominant inheritance
A
these traits are more common in females than males and do not skip generations. Affected fathers will always pass the trait to daughters but never to sons. Affected mothers will pass the trait to both daughters and sons.
13
Q
Define X-linked recessive inheritance
A
these traits are more common in males than females and can skip generations. Affected fathers cannot pass the traits to sons but the daughters will at least be carriers of the condition. Affected mothers will always pass the trait to sons and daughters will at least be carriers.
14
Q
Define y-linked inheritance
A
these traits are not common. Women are never affected. Affected fathers will pass the trait to all of their sons.
15
Q
define mitochondrial inheritance
A
although these traits are not common, they affect both males and females. Mitochondria which are the powerhouses of the cell have their own DNA which can be passed on. However, the trait is only passed from mothers to their offspring. Fathers can be affected but will not be able to pass the trait to offspring.
15
Q
define mitochondrial inheritance
A
although these traits are not common, they affect both males and females. Mitochondria which are the powerhouses of the cell have their own DNA which can be passed on. However, the trait is only passed from mothers to their offspring. Fathers can be affected but will not be able to pass the trait to offspring.
16
Q
What is a zygote?
A
a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum. contains the human genome.
17
Q
What are chromosomes?
A
Chromosomes are the structures that hold genes.
18
Q
What are genes?
A
Genes are the individual instructions that tell our bodies how to develop and function
19
Q
T or F: Many chromosomes have two segments, called “arms,” separated by a pinched region known as the centromere. The shorter arm is called the “p” arm. The longer arm is called the “q” arm.
A
True
20
Q
What is the typical number of chromosomes in a human cell?
A
46, 23 pairs
21
Q
The first 22 pairs of chromosomes are called what?
A
Autosomal
22
Q
The final pair of chromosomes is called
A
Sex Chromosomes.
23
Q
A picture or chromosome map is called a
A
A karyotype
24
T or F: n the past decade, newer techniques have been developed that allow scientists and doctors to screen for chromosomal abnormalities without using a microscope. These newer methods compare the patient's DNA to a normal DNA sample. The comparison can be used to find chromosomal abnormalities where the two samples differ. One such method is called noninvasive prenatal testing. This is a test to screen a pregnancy to determine whether a baby has an increased chance of having specific chromosome disorders. The test examines the baby's DNA in the mother's blood.
True
25
Explain the difference between numerical abnormalities and structural abnormalities
Numerical Abnormalities is when an individual is missing one of the chromosomes from a pair, the condition is called monosomy. When an individual has more than two chromosomes instead of a pair, the condition is called trisomy but these are both numerical abnormalities.
26
Explain the difference between monosomy and trisomy
monosomy is when you are missing on one of the chromosomes and trisomy is when an individual has more than a pairs, such as 3 chromosomes. Examples for trisomy is having more than one pair. Monosomy is when missing a chromosome.
27
Name some trisomy abnormalities
Down syndrome, also known as Trisomy 21, Edward syndrome, and Patau syndrome.
28
Name a monosomy abnormality that could occur
Turner syndrome. Monosomies are missing one chromosome. Cells are sensitive to the loss of a chromosome. The only viable loss of a chromosome is on the sex chromosome for Turner syndrome. Turner's syndrome is significantly lower than that of sex chromosome trisomies, suggesting that a single X chromosome is insufficient for optimum cell function. These individuals are usually mosaics.
29
What are structural abnormalities?
When a chromosomes structure are altered. This can be from deletions, translocations, duplications, inversions, or rings.
30
Most chromosome abnormalities occur as an accident in the egg or sperm. Some abnormalities, however, happen after conception; T or F
True
31
Chromosome abnormalities can be inherited from a parent (such as a translocation) or be "de novo" (new to the individual). This is why, when a child is found to have an abnormality, chromosome studies are often performed on the parents.
True
32
T or F: As paternal age increases, it can increase the chance of having children with chromosome abnormalities.
False. Maternal Age can because Women are born with all the eggs they will ever have. Some researchers believe that errors can crop up in the eggs' genetic material as they age. Older women are at higher risk of giving birth to babies with chromosome abnormalities than younger women. Because men produce new sperm throughout their lives, paternal age does not increase risk of chromosome abnormalities.
33
T or F: Chromosomal abnormalities can also cause miscarriage, disease, or problems in growth or development.
True
34
the major chromosomal aneuploidies seen in live-born babies are:
trisomy 21 (Down syndrome), trisomy 18; trisomy 13; 45, X (Turner syndrome); 47, XXY (Klinefelter syndrome); 47, XYY; and 47, XXX.
35
what are the rings in chromosomal abnormalities?
when a chromosome undergoes two breaks and the broken ends fuse into a circular chromosome
36
What is an isochromosome?
An isochromosome can form when an arm of the chromosome is missing and the remaining arm duplicates.
37
explain balanced rearrangements
Balanced rearrangements include inverted or translocated chromosomal regions. Since the full complement of DNA material is still present, balanced chromosomal rearrangements may go undetected because they may not result in disease. A disease can arise as a result of a balanced rearrangement if the breaks in the chromosomes occur in a gene, resulting in an absent or nonfunctional protein, or if the fusion of chromosomal segments results in a hybrid of two genes, producing a new protein product whose function is damaging to the cell.
38
Most aneuploids are lethal. True or false.
True. Researchers now appreciate that aneuploid gametes are produced at surprisingly high rates in human meioses, and that very few aneuploid embryos are able to survive. In fact, trisomies represent about 35% of spontaneous abortions. Indeed, the only other autosomal trisomies besides 21 that are detected in any appreciable numbers among newborns involve chromosomes 13 and 18, but affected babies rarely survive beyond the first few months of life (Hassold & Hunt, 2001).
39
Who was John Langdon Down?
Viable trisomies are restricted to only a few human chromosomes. The most common human trisomy involves chromosome 21 and is known as Down syndrome (DS), named for John Langdon Down, the physician who first described the condition in 1866. Interestingly, almost a century elapsed between the clinical description of DS and its association with trisomy 21.
40
Why do sex chromosome abnormalities seem to do better than autosome abnormalities?
Humans are much more able to tolerate extra sex chromosomes than extra autosomes. Thus, after DS, the most common human aneuploidy is the condition known as Klinefelter's syndrome (Jacobs & Strong, 1959). Klinefelter's males have a total chromosome number of 47, which includes two X chromosomes and one Y chromosome. According to convention, these males are designated as 47,XXY individuals. Other configurations of the sex chromosomes have been observed in 47,XXX females and 47,XYY males. Compared to autosomal trisomies, these sorts of sex chromosome trisomies are fairly benign. Affected individuals generally show reduced sexual development and fertility, but they often have normal life spans, and many of their symptoms can be treated by hormone supplementation. The ability of humans to tolerate supernumerary sex chromosomes is quite remarkable, as individuals can survive with as many as four sex chromosomes. This tolerance most likely relates to both X inactivation and to the small number of genes on the Y chromosome. In fact, when cells from individuals with more than one copy of the X chromosome are analyzed under a microscope, all but one of the X chromosomes appear as condensed Barr bodies, the cytological manifestations of X-chromosome inactivation. Supernumerary copies of the Y chromosome may be tolerated because the few gene products of the Y chromosome are not required for survival.
41
What is mosaicism in turner syndrome?
When the chromosome is partially missing rather than fully missing. In mosaic Turner syndrome, an X chromosome is missing in some cells in people assigned female at birth.
42
What is G-banding?
When reading a karyotype, The dye stains regions of chromosomes that are rich in the base pairs Adenine (A) and Thymine (T) producing a dark band. A common misconception is that bands represent single genes, but in fact the thinnest bands contain over a million base pairs and potentially hundreds of genes. For example, the size of one small band is about equal to the entire genetic information for one bacterium.
43
What is a genetic disorder?
A genetic disorder is a condition that is caused by an abnormality in an individual's DNA. Abnormalities can be as small as a single-base mutation in just one gene, or they can involve the addition or subtraction of entire chromosomes.
44
Explain the general issues that arise with chromosomal abnormalities?
A lot of times issues arrive with entire sections of chromosomes such as deletion, or duplication, or translocation. Sometimes this wont show until later down the line.
45
When does Robertsonian translocation cause problems?
Usually the affect happens down the line when you pass down the section because it is missing a part.
46
The difference between Aneuploid vs. Polyploid
Aneuploid is 1 or maybe 2 chromosomes missing. Polyploid is an entire set missing.
47
Examples of disorders with trisomies (extra copy)
Trisomy 21 (Down syndrome), Edwards syndrome, Patau syndrome, trisomy X, klienfelter, xyy syndrome
48
Examples of disorders with monosomes (only 1 copy)
Turner syndrome
49
What are the main risk factors for trisomy and monosomy disorders?
Maternal age and environmental factors.
50
What does a blank square on the pedigree analysis mean?
Male with no expression or sign of the trait
51
What does a filled circle on the pedigree analysis mean?
Female with expression
52
What does the horizontal line that connects a circle to a square?
That means they mated, possibly were married.
53
Name the types genetic or genomic testing.
carrier testing, diagnostic, or predictor testing. Carrier (Color Blindness) : you want to know if you are a carrier based on history. Diagnosis (DMD) : you have symptoms and want to confirm. Predictive: finding out your risk for a disease. (BRCA genes, Diabetes)
54
What kind of prenatal testing are there?
PGD, and Amniocentesis. They want to know that their embryo will be viable.
55
Explain PGD
Only in IVF. Preimplantation Genetic Diagnosis. Labaratory procedure that checks for inherited conditions
56
Explain Amniocentesis
Second trimester. A needle that takes amniotic fluid. This is diagnostic and tells what will happen.
57
Explain Carrier Testing
May be higher because of ethnicity. You can test if you are a carrier for color blindness, sickle cell anemia, and more.
58
Explain newborn screening
For a newborn. Very common. Happening since the 1960's. Dr. Robert Guthrie started this for PKU. They do a quick blood test for certain risk factors for
59
Name the cons to Direct to consumer tests.
They lack informed consent. Sometimes the tests are not completely accurate. Results could be misunderstood without genetic counseling. There is no to little follow up care.
60
False negatives and false positives never happen. T or F
False! They do happen so we should be careful when deciding.
61
CLIA certified laboratories are the best to be trusted. T or F
True. They will be better than research labs that don't have that.
62
What is the difference between genetics and genomics?
genetics is the study of how a gene and it's trait is inherited. Genomics is the study is what a gene does after you have already inherited it.
63
What is the difference between molecular testing, chromosomal testing, and biochemical testing?
Molecular is designed to look at the DNA sequence to see if the disease is present. Chromosomal is designed to look for defects on the entire chromosome such as a karyotype. Biochemical includes indirect testing for certain proteins, or chemical products of a gene in the blood that can help to diagnose. (for example, newborn screenings)
64
Explain what triploid is?
A rare condition where a cell has 69 total chromosomes instead of 46.
65
How do you calculate for a triploidy chromosome count?
Ploidy chromosome count = (Diploid Count) / 2 x (Prefix Number (di, tri, etc. 2, 3,)
66
What was discovered by Dorothy Anderson in 1938 ?
Sickle Cell Anemia
67
What symptoms describe DMD ?
Progressive muscle weakness, difficulty standing up, gradual loss of motor control, and apparent enlargment of the muscles.
68
what is the gene associated with achondroplasia?
FGFR3
69
Which protein is associated with PKU?
Phenylalanine Hydroxylase
70
Which chromosomal disorder results in an individual with a small head, severely reduced mental capacity, kidney malformations, clenched fists with overlapping fingers, and widely-spaced, narrow eyes?
Edwards syndrome
71
How do you calculate for a somy chromosome count?
Somy chromosome count = (Diploid Count (44 for human) - 2 + (Prefix Number)
72
What is FISH testing?
Short strands of ssDNA attached to special glowing proteins bind to a complementary segment of DNA on a chromosome, identifying the presence or absence of an allele when examined under a powerful microscope.
73
What are inversions?
A piece of a chromosome that breaks off, flips over, and reattaches backwards to the chromosome.
74
Which of the following is an event that leads to a chromosome having multiple copies of one or more of its genes?
Duplication
75
Which diseases are inherited in a autosomal recessive pattern
Phenylketonurea
Sickle Cell Disease
Cystic Fibrosis
76
An individual with four copies of one of their chromosomes is said to exhibit __________.
Tetrasomy
77
Genetic testing in the United States is overseen by four government agencies. Which ones?
CDC, Office of Human Research Protections, FDA, and Centers for Medicare and Medicaid Services
78
What is tested in the newborn screening?
Cystic Fibrosis
Phenylketonuria
Sickle Cell Disease
79
How many is Tetra?
Four
80
Explain what does the term ploidy mean?
Determine what the creature's ploid # is. That would be equal to the number of chromosomes that the creature has. Humans have 23 chromosomes so their ploid value is = 23.
81
if something is di-ploid that means 3x23 for a human yes?
No. di is 2. so you would do 23x2 = 46
82
How many is mono
one
83
How many is tri-ploidy for a human which isn't actually possible but can be for plants?
23x3 = 69
84
Haploid and mono-ploid is this same thing. True or false?
True. That means they only have ONE pair of chromosomes.
85
Who were Dr. James B. Herrick, Walter Clement Noel, and Dr. Earnest e. irons?
The first to identify Sickle Cell anemia around 1904 when Walter came in.
86
SCD is caused by mutations in which gene?
HBB
87
which inherited condition causes the deformation of red blood cells (RBCs) into a sickle shape, resulting in
decreased RBC lifespan and hemolysis.
Sickle Cell Anemia
88
Sickle cell disease is inherited in an autosomal recessive pattern, which means
that a child is born with SCD only when they inherit 2 defective copies of the
sickle cell gene (1 from each parent). true or false
True.
89
If both parents are carriers, there is a 25% risk of having a child with SCD, a 50%
risk of having a child who is a carrier, and a 25% chance of having a normal child
without an HBB gene mutation. True or False
True
90
Sickle Cell Anemia is found on which chromosome
11
91
How can sickle cell anemia be found?
Through a blood test
92
Muscular Dystrophy is found on which chromosome
It is on the X chromosome (23).
93
Guillaume Benjamin Amand Duchenne first described DMD.
True or False
True
94
Distrophin is the protein contributing to what?
Muscular Dystrophy
95
What is the gene loci for MD
XP21.2 1
96
More women than men have muscular dystrophy. True or False.
False. More men wil have it because it is x-linked inheritance.
97
What are the symptoms of Achondroplasia
It is the most common form for dwarfism. It includes shorter limbs, larger heads, poor muscle tone, curved lower spine, and misaligned teeth
98
Achondroplasia was first found in the 1950's. T or F
False. It was first described in 1879.
99
Where is achondroplasia found in the human chromosome?
It is found on the FGFR3 gene which is on
Chromosome 4
100
What kind of testing is needed to confirm Achondroplasia?
DNA testing is usually needed to confirm which kind of achondroplasia.
101
When was hemophilia recognized as a condition?
1800's but it was seen and noted well before then
102
The name "hemophilia" was first used in 1828 by Dr. Friedrich Hopff. T or F
True
103
Explain what hemophilia is
Hemophilia is a genetic disorder that impairs the body's ability to
control blood clotting. There are two types of hemophilia. Hemophilia A and Hemophilia B.
104
Both types of Hemophilia are autosomal recessive. True or False.
False. They are x-linked recessive traits. This disease is more common in males and passed down through the maternal line. Still, the disease wont manifest unless both parents pass it down.
105
Cystic Fibrosis was first diagnosed in what year?
1938
106
Cystic Fibrosis was recognized by what symptoms?
a white swollen pancreas, fluid filled sacs, scar tissue. lung infections could be fatal so they have trouble breathing.
107
Cystic Fibrosis is autosomal dominant. True or False.
False. It is autosomal recessive.
108
Which gene and chromosome is attributed to Cystic Fibrosis?
TFR gene. Chromosome 7
109
What is phenylketonuria?
also called PKU is intellectual disability, seizures, delayed development, behavioral problems, eczema
110
When was PKU first discovered?
Dr. Asbjorn Folling in 1934
111
PKU is autosomal recessive. True or False
True.
112
PKU is caused by mutations in the PAH gene
True.
113
The PAH gene responsible for PKU is found on chromosome 13.
False. It's chromosome 12.
114
What is Tay Sachs?
a genetic condition where too much fat develops in the brain
