Lect 24 Flashcards
1
Q
What is the typical karyotype for humans?
A
46, XX or 46, XY
46, XX indicates a female karyotype, while 46, XY indicates a male karyotype.
2
Q
How many base pairs do humans have in total?
A
6 billion
Humans inherit 3 billion base pairs from each parent.
3
Q
How many base pairs do humans inherit from each parent?
A
3 billion
This contributes to the total of 6 billion base pairs.
4
Q
How many genes does the human genome contain?
A
About 20,000 genes
5
Q
Is the specific location of each gene on a chromosome predetermined?
A
No, it is the result of evolutionary processes
6
Q
What shapes the arrangement of genes on chromosomes?
A
Evolutionary history
7
Q
What is the exception to the random arrangement of genes on chromosomes?
A
The male-determining gene (the SRY gene)
8
Q
On which chromosome is the SRY gene located?
A
Y chromosome
9
Q
What is essential for male development in relation to the SRY gene?
A
The presence of the SRY gene on the Y chromosome
10
Q
Fill in the blank: The arrangement of genes is somewhat _______.
A
random
11
Q
True or False: The SRY gene can be located on any chromosome for male development.
A
False
12
Q
What is the largest human chromosome?
A
Chromosome 1
13
Q
How many base pairs does Chromosome 1 span?
A
Approximately 250 million base pairs (Mbp)
14
Q
What percentage of the human genome does Chromosome 1 make up?
A
About 8%
15
Q
How many genes are contained in Chromosome 1?
A
Around 2,033 genes
16
Q
How many phenotypes are associated with mutations in the genes of Chromosome 1?
A
465 phenotypes
17
Q
Fill in the blank: Chromosome 1 is associated with _______ phenotypes caused by mutations in its genes.
A
465 phenotypes
18
Q
True or False: Chromosome 1 is smaller than all other human chromosomes.
A
False
19
Q
What is the length of Chromosome 21?
A
48 Mbp
Mbp stands for megabase pairs, a unit of measurement for DNA sequences.
20
Q
How many genes are located on Chromosome 21?
A
233 genes
Genes are segments of DNA that contain the instructions for building proteins.
21
Q
How many phenotypes are associated with Chromosome 21?
A
45 phenotypes
Phenotypes refer to the observable traits or characteristics of an organism.
22
Q
What is the most common form of intellectual disability?
A
Down syndrome
23
Q
How often does Down syndrome occur in births?
A
About 1 in 800 births
24
Q
What genetic anomaly causes Down syndrome?
A
An extra copy of chromosome 21 (trisomy 21)
25
What causes the extra chromosome in Down syndrome?
A random mutation in either the mother's or father's genetic material
26
Are parents of a child with Down syndrome typically affected by the condition?
No, the parents are typically unaffected
27
What are the phenotypes associated with Down syndrome?
Intellectual disability and physical traits
28
Fill in the blank: Down syndrome is caused by an extra copy of _______.
chromosome 21
29
What is the karyotype for Down syndrome in females?
47,XX,+21
## Footnote
This indicates there are 47 chromosomes, with two X chromosomes and an extra chromosome 21.
30
What is the karyotype for Down syndrome in males?
47,XY,+21
## Footnote
This indicates there are 47 chromosomes, with one X and one Y chromosome, and an extra chromosome 21.
31
What is Down syndrome also known as?
Trisomy 21
32
What causes Down syndrome?
Non-disjunction of chromosome 21 during meiosis
33
What happens during non-disjunction in Down syndrome?
An extra copy of chromosome 21 is inherited
34
How many copies of chromosome 21 do individuals with Down syndrome have?
Three copies
35
What is the usual number of chromosome 21 copies in humans?
Two copies
36
Why can individuals with Down syndrome survive?
The reason individuals with Down syndrome can survive is that chromosome 21 is the smallest human chromosome, containing the least number of genes
37
What is the mistake called when chromosomes fail to properly segregate during meiosis?
Non-disjunction
## Footnote
Non-disjunction can lead to conditions such as trisomy 21.
38
What is trisomy 21 commonly known as?
Down syndrome
## Footnote
Down syndrome is caused by having three copies of chromosome 21.
39
What happens to the egg during non-disjunction in the case of Down syndrome?
The egg may end up with two copies of chromosome 21, or none at all
## Footnote
This results in aneuploid eggs.
40
What is the result when an aneuploid egg is fertilized?
The resulting offspring will have three copies of chromosome 21
## Footnote
Two from the mother and one from the father.
41
Why is Down syndrome more common in older mothers?
The longer eggs remain in prophase, the greater the likelihood of errors during meiosis
## Footnote
Older mothers have eggs that have been in prophase longer.
42
What is the term for the suspended state of eggs until ovulation occurs?
Prophase
## Footnote
Eggs remain in prophase from birth until ovulation after puberty.
43
What is one method to test if a mother is carrying a child with Down syndrome?
Non-Invasive Prenatal Testing (NIPT)
## Footnote
NIPT analyzes small fragments of the embryo's DNA in the mother's blood.
44
What does the Non-Invasive Prenatal Testing (NIPT) analyze?
Small fragments of the embryo's DNA that circulate in the mother's blood
## Footnote
This can detect the likelihood of trisomy 21.
45
Fill in the blank: The condition caused by having three copies of chromosome 21 is known as _______.
Down syndrome
46
What is monosomy 21?
A lethal condition that does not survive to birth
## Footnote
Monosomy 21 occurs when the egg has no copy of chromosome 21.
47
What happens after fertilization in monosomy 21?
The embryo only receives one copy of chromosome 21 from the father
## Footnote
This results in a non-viable embryo.
48
True or False: Monosomy 21 is compatible with life.
False
## Footnote
Monosomy 21 leads to a lethal condition that cannot survive to birth.
49
What is a significant outcome of monosomy 21?
It does not survive to birth
## Footnote
This is due to the lack of a second copy of chromosome 21.
50
What is the expression level of protein for individuals with trisomy 21 compared to unaffected individuals?
Individuals with trisomy 21 express ~1.5x as much protein for each gene on chromosome 21
## Footnote
This indicates a significant overexpression of genes located on chromosome 21.
51
List all examples of genetic disorders or conditions that are caused by mutations in specific genes as a result of DOWN SYNDROME
These are all examples of genetic disorders or conditions that are caused by mutations in specific genes. Each of these genes is associated with a particular phenotype or medical condition:
1. KCNE2 - Long QT Syndrome: A genetic condition that affects the heart
2. CSTB - Epilepsy
3. PCNT2 - Osteodysplastic Dwarfism
4. APP - Alzheimer's Disease
5. RUNX1 - Acute Myeloid Leukemia (AML)
52
What is trisomy 18 commonly known as?
Edward syndrome
## Footnote
Trisomy 18 leads to severe developmental issues and is often lethal.
53
What is trisomy 13 commonly referred to as?
Patau syndrome
## Footnote
Patau syndrome is associated with significant physical and intellectual disabilities.
54
What genetic condition is represented by XYY?
XYY syndrome
## Footnote
XYY syndrome may be linked to taller stature and some behavioral issues.
55
What does XXY signify in genetic terms?
Klinefelter syndrome
## Footnote
Klinefelter syndrome can lead to infertility and physical differences.
56
What is trisomy X also known as?
triple X syndrome
## Footnote
Triple X syndrome may result in taller women and potential learning difficulties.
57
Which trisomies are non-lethal?
* trisomy 21
* trisomy 18
* trisomy 13
* XYY syndrome
* XXY (Klinefelter syndrome)
* trisomy X
## Footnote
All other trisomies are considered lethal.
58
What is monosomy X commonly referred to as?
Turner syndrome
## Footnote
Turner syndrome affects females and can lead to short stature and infertility.
59
True or False: All other monosomies besides monosomy X are lethal.
True
## Footnote
Monosomies typically lead to severe developmental issues and are not viable.
60
What is sickle cell anemia?
A genetic disorder in which red blood cells become abnormally shaped, adopting a sickle shape under low oxygen conditions.
61
What shape do normal red blood cells have?
Disc, flexible and round.
62
What happens to red blood cells under low oxygen conditions in sickle cell anemia?
They adopt a sickle shape.
63
Why do sickle-shaped red blood cells cause problems in the body?
They are rigid and cannot deform properly, causing blockages in small blood vessels.
64
What are the potential consequences of blockages caused by sickle-shaped red blood cells?
Pain and organ damage.
65
How does the body respond to defective red blood cells in sickle cell anemia?
By attempting to remove them via the spleen.
66
How does sickle cell anemia affect bone marrow?
It leads to bone marrow expansion due to the ongoing need for blood cell production.
67
What skeletal issues may arise from sickle cell anemia?
Skeletal deformities.
68
what damage is caused by sickle cells anemia?
This blockage can lead to ischemia (restricted blood flow), pain, and organ damage. The body attempts to remove the defective red blood cells by the spleen, but over time, this can lead to autosplenectomy (shrinkage or loss of the spleen) due to repeated damage. The liver may also become overworked, resulting in liver damage and jaundice (yellowing of the skin and eyes).
Blockages in blood vessels can cause dactylitis (swelling of the fingers and toes), and the ongoing need for the body to produce more blood cells can lead to bone marrow expansion, which may cause skeletal deformities.
69
What is sickle cell anemia caused by?
A mutation in the HBB gene
70
What does the HBB gene code for?
The β-globin subunit of hemoglobin
71
What are the components of hemoglobin?
Two α-subunits (HBA) and two β-subunits (HBB)
72
What effect does the mutation in the HBB gene have on hemoglobin?
Causes hemoglobin to form abnormal shapes under low oxygen
73
What shape do red blood cells take as a result of sickle cell anemia?
Sickle-shaped
74
What type of genetic condition is sickle cell anemia?
Autosomal recessive
75
How many copies of the mutated gene are required for sickle cell anemia to occur?
Two copies (one from each parent)
76
What does haemoglobin contain that binds oxygen?
An iron incorporating haem group
## Footnote
The haem group is essential for oxygen transport in the blood.
77
What is the structural composition of haemoglobin?
A tetramer of two α-subunits and two β-subunits
## Footnote
This structure allows haemoglobin to effectively bind and release oxygen.
78
Sickle cell anaemia is caused by a mutation in haemoglobin β. Explain what this mutation is
79
What is sickle cell disease caused by?
A mutation in the hemoglobin β gene (HBB)
## Footnote
Specifically a single base change in the 6th codon.
80
What is the normal codon for glutamic acid?
GAG
81
What codon replaces glutamic acid in sickle cell disease?
GTG
82
What amino acid does the codon GTG code for?
Valine
83
How does glutamic acid differ from valine in terms of properties?
Glutamic acid is acidic; valine is hydrophobic
84
In hemoglobin electrophoresis, how is hemoglobin separated?
Based on its charge
85
What is the charge of normal hemoglobin (HbA)?
Negatively charged
86
How does normal hemoglobin (HbA) behave in the electric field during electrophoresis?
Typically doesn't move much, stays near the origin at the positive charge
87
What is the charge of sickle cell hemoglobin (HbS)?
Positive charge
88
How does sickle cell hemoglobin (HbS) move in the electric field?
Moves towards the negative electrode, as it is has positive charge
89
What do red cells lack?
Cytoskeleton
## Footnote
Red blood cells do not have a cytoskeletal structure.
90
What structure does α2β+2 form in red blood cells?
An ordered stack providing strength
## Footnote
This structure helps maintain the integrity of red blood cells.
91
What does α2βs2 form in low O2 conditions?
A more stable polymer
## Footnote
This polymerization process enhances the stability of red blood cells under low oxygen levels.
92
How do polymers affect red blood cells?
They physically distort the red blood cell
## Footnote
This distortion can impact the functionality of red blood cells.
93
What disease has a strong relationship to ethnicity?
Sickle cell disease
## Footnote
This relationship is particularly noted in populations from malaria-prone areas.
94
Sickle cell disease is prevalent in populations with origins in areas where _______ is or was prevalent.
Malaria
## Footnote
The connection between sickle cell disease and malaria offers insights into its evolutionary advantages.
95
What phenotype can be induced in heterozygotes under very low oxygen conditions?
Sickle phenotype
## Footnote
Heterozygotes carry one normal allele and one sickle allele, leading to this phenotype under specific conditions.
96
What does homozygotes for the βs mutation result in?
Severe diseases
## Footnote
Homozygotes have two copies of the sickle cell allele, which results in a more severe form of the disease.
97
What should be done with the βs allele in a population?
Selected against and lost from the population
## Footnote
This suggests that the allele is detrimental and should not persist in healthy populations.
98
What does the invasion of the parasite malaria cause in sickle trait cells?
The cells to sickle
99
Why does the malaria parasite not grow well in sickle cells?
Because sickle cells and the parasite are cleared more rapidly by the spleen
100
What is the role of the spleen in relation to sickle cells and the malaria parasite?
The spleen clears both sickle cells and the malaria parasite more rapidly
101
What is the first step in the gene therapy process for sickle cell disease?
Collecting a patient’s bone marrow cells
## Footnote
This process is essential for obtaining the cells that will be modified in the lab.
102
What do scientists modify the bone marrow cells to reactivate in sickle cell gene therapy?
The fetal hemoglobin gene
## Footnote
Reactivating this gene is crucial as it produces hemoglobin that does not sickle.
103
Why is fetal hemoglobin important in the treatment of sickle cell disease?
It doesn’t sickle, helping to prevent the symptoms of the disease
## Footnote
Fetal hemoglobin provides a functional alternative to sickle hemoglobin.
104
What happens to the edited cells after modification in the lab?
They are returned to the patient
## Footnote
This step is necessary for the patient to start benefiting from the therapy.
105
What type of red blood cells do the modified cells begin to produce?
Red blood cells with fetal hemoglobin
## Footnote
These cells are crucial for alleviating symptoms associated with sickle cell disease.
106
What long-term benefit does the gene therapy provide for sickle cell disease patients?
Long-term relief from sickle cell disease
## Footnote
The therapy aims to improve the quality of life for patients over time.
