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Flashcards in Genetics - Campbell Deck (29):
1

Give two examples of differences between identical twins that illustrate that despite their being very nearly identical genetically, environment also plays a role in their development and health.

Fingerprints.
Type-1 Diabetes.

2

How many chromosomes are there? How many of them are X chromosomes? How many of them are Y chromosomes? How many of them are autosomes? What is an autosome?

46 chromosomes.
22 called pairs.
In women - 2 X
In guys - one Y, one X

Autosomes are everything but the X and Y (so 22 pairs).

3

Name four trisomies for which a live birth is possible. Which of these produces mild to undetectable symptoms?

(Trisomy 13, 18, 21, X)
Down Syndrome

Sex ones:
Klinefelter Syndrome (XXY)
Turner Syndrome (only one x)
XXX and XYY ** (mild trisomy, tall, and can bear children)

4

Trisomy of which number chromosome is called Down syndrome?

21

5

What is XYY Syndrome?

A mild syndrome that results in a male having an extra Y chromosome. Mild, tall, can bear children.

6

Trisomy of which number chromosome is Klinefelter Syndrome? What are the affects?

XXY; Results in testicular failure.

7

What is Turner Syndrome?

A variable disease with only one X chromosome (As to the normal XX or XY)

8

How does inheritance of an X-linked disease differ form inheritance of an autosomal disease? How does inheritance of a mitochondrial disease differ from inheritance of an autosomal disease?

Inheritance of X-linked disease runs only on the X gene, making the inheritance gender dependent. There is a lack of male-to-male transmission, and females are generally protected from X-linked diseases [via the bystander effect], unless it is skewed.

In mitochondrial diseases, the defective gene is on the mitochondrial DNA, which mean it is a strictly maternal inheritance.

9

Which will probably have the greatest number of offspring who suffer from an inherited disease? (may be more than one)

A. parents both heterozygous for an autosomal recessive disease
B. parents both heterozygous for an autosomal dominant disease
C. a father who suffers form an X-linked recessive disease and a mother who is homozygous wild-type (has only the well form of that disease gene)
D. A mother who is heterozygous for an X-linked recessive disease and a father who is wild-type hemizygous (has the well form of that disease gene)
E. a father who suffers from a mitochondrial disease and a mother who does not (does not at all).

Of each of these, which will probably have the least number of offspring who suffer form an inherited disease (may be more than one)?

Suffer the most:
B. parents both heterozygous for an autosomal dominant disease

Suffer the least:
E. a father who suffers from a mitochondrial disease and a mother who does not (does not at all).

10

Explain how penetrance might mean that no individuals with disease symptoms are observed in the following pedigree. Define genotype and phenotype, and tell how the statement "the phenotype differs from the genotype" applies to this situation.

Penetrance is how genes influence the quantitive affect.

Phenotype is what shows
Genotype are the actual genes


There can be differences in the phenotype and genotype, meaning that what is expressed by the gene is not the expected level.

Examples:
Accute intermitant porphoryia: low penetrance
(only 20% of people with bad genes actually show the disease


..........

11

What environmental factors affect penetrance of hereditary hemochromatosis?

Dietary iron. With a normal level of iron intake, uptake of iron intake will be increased causing an overload the iron.

12

Why does an X-linked disease such as Duchenne muscular dystrophy seldom cause symptoms in females?

Because the Duchenne muscular dystrophy disease is an X-linked recessive disease and women have two X-chromosomes, women are less likely to exhibit symptoms than males.

13

A new inherited disease has been discovered in which disease occurs only when the effect is inherited from the father. The disease gene is most likely:

A. autosomal dominant
B. autosomal recessive
C. X-linked recessive
D. mitochondrial
E. imprinted

E. imprinted

This is an example of Prader Willi syndrome (disease comes from father), caused by methylation defects.

An imprinted disease from the mother is called Angelman syndrome.

14

Explain what is meant by "a genetic disease that is never inherited."

A genetic disease that is not inherited (Proteus Syndrome) means that if it is inherited, every cell in the body would be affected, so it is lethal. This defect likely happened early on causing in a birth in

15

What disease is a genetic disease in which the mutations that cause it often occur AFTER birth (discussed further in lecture)?

Proteus Syndrome.

16

What type of inheritance is involved in the following:

Tay Sachs disease?
cystic fibrosis?
hereditary hemochromatosis?
Duchenne muscular dystrophy?
Hungtington disease?
Leber hereditary optic neuropathy?

Tay Sachs disease:autosomal recessive

cystic fibrosis: Autosomal recessive

hereditary hemochromatosis : Autosomal Recessive

Duchenne muscular dystrophy: X-linked recessive

Hungtington disease: Autosomal Dominant

Leber hereditary optic neuropathy: mitochondrial defect that is most often seen in males

Familial hypercholesterolemia: Autosoma Dominant

17

Describe the genetic defect that result in Huntington disease (what is there more of in terms of nucleotides and of aminoacids)?

Triple Nucleotide Repeat disease. CAG (glutamine), which has 100% penetrance.

If the number of repeats is < 35; good.
If the number of repeats > 36 ; bad

18

What is the most common inherited disease in the USA? Is it sometimes fatal without treatment? What is the most common lethal inherited disease in the USA (invariably lethal at some age; average age fo death in the 30s; few affected individuals survive into their 40s and 50s)?

Most common inherited disease in USA: hereditary hemochromatosis

Most common lethal inherited disease in the USA:
cystic fibrosis

19

What protein is defective in cystic fibrosis? In what organs is the defect most problematic? What problem generally causes death in cystic fibrosis patients? What does the protein do that promotes this eventually fatal problem?

In cystic fibrosis, there is a defect in the protein cystic fibrosis transmembrane conductance regulator (CFTR). Problems occur in the pancreas and liver, with pancreatic insufficienty leading to malabsorption and constant lung infections, which makes the lung extremely fibrotic. In cystic fibrosis, the lack of CFTR leads to the bacteria P. aeruginera build up and infecting the lungs.

In the small intestion, however, the lack of CFTR prevents S. typhi bug from being brough tinto the small intestine, causing it to be urinated out.

20

What enzyme is defective in Tay Sachs disease? What builds up (and where does it build up) as a result? What are the symptoms? Is this the only enzyme involved in trimming sugars off of glycosphingolipids that when defective leads as disease? What is the class of disease known as?

Mutations in HEXA gene result in a deficiency of
beta-N-acetylhexosaminidase A, which builds up glycosphingolipids. Symptoms include neural deterioration , mental retardation, red spot on retina, paralysis, muscle atrophy, blindness, pancreatic insufficiency, and lung damage.

This is an autosomal recessive disease/ sphingolipid storage disorder.

(Bill)

21

Gives three examples of diseases mentioned in the heandout that can be caused by a single gene defect (monogenic) or by the combined effect of many genes (polygenic). Name the other diseases mentioned in lecture handout that are only polygenic.

Monogenic OR polygenic:
Hypertension
Cardiovascular disease
Type 2 Diabetes

Only Polygenic:
Neural tube defects (ancencephaly and spina bifida)
Developmental defects (cleft-lip/palate)
ALcoholism
Asthma
Bipolar disorder
INherited epilepsy
Idopathic gout
Obesity
Type I Diabetes.

22

Name three inherited monogenic disease that cause hypertension, typically causing very high blood pressure in very young individuals. Name the polygenic syndrome that is generally considered to be the cause of most hypertension.

Monogenic syndrome:
Glucocorticoid-remediable aldosteronism
Apparent mineralcorticoid excess
Liddle syndrome

Polygenic syndrome:
Essential Hypertension

23

Name a class of genes that has been found to be associated with type 1 diabetes. Name the class of genes that have been found to be associated with a monogenic disease that may be thought of as type 2 diabetes (hint-think young). Name one gene that has been found to be associated with the development of polygenic type 2 diabetes. One form of this type of diabetes is found in approximately 85% of the world population. Is this prevalent form protective against or predisposing to developing diabetes?

Type 1 Diabetes: an autoimmune disease.
- Polygenic: Human Leukocyte antigen (immune system)

Type 2:
- Monogenic:
Type 1 Diabetes:
Type 2 Diabetes: MODY genes (MODY 1 ...to... MODY 7)

- Polygenic:
PPAR-gamma
The bad form of PPAR-gamma is found in 85% of the population, this form is predisposing to developing diabetes

24

Which of the following infectious diseases is NOT thought to be protected against by an inherited genetic mutation or deletion (may be more than one)?
A. HIV
B. typhoid fever
C. anthrax
D. malaria
E. leprosy

Anthrax

25

For which of the following infectious diseases is there inherited protection against? Name the gene in which mutation is thought to be protective.
A. HIV
B. typhoid fever
C. anthrax
D. malaria
E. leprosy

A. HIV (CCR5)
B. Typhoid Fever ( cystic fibrosis)
D. Malaria ( sickle cell disease)

(? Bill)

26

You explain to a patient that they do not have the form of the gene that causes Huntington disease, and that they have 20 repeats in their gene. The patient says that they have heard about a "gray area" in those tests, and asks if their results is really certain. You should explain that.

A. the test is expensive and therefore reliable
B. their neurological function tests confirmed the result
C.some people have an intermediate nubmer of repeats (in the mid-30s) and for those individuals it is indeed uncertain whether or not they will someday suffer disease symptoms. The results of the test are definitive for someone with 20 repeats.
D. whenever there is Huntington disease in a close relative, the results of screening must be viewed as unreliable.
E. there is no gray area to these tests.

C.some people have an intermediate nubmer of repeats (in the mid-30s) and for those individuals it is indeed uncertain whether or not they will someday suffer disease symptoms. The results of the test are definitive for someone with 20 repeats.

(Bill)

27

You are treating a case of erythroblastosis fetalis, a disease of the fetus in pregnancy. This is most often caused by isoimmune reaction to the D antigen, which is one of the antigens responsible for the Rh blood group. Antibodies developed in an Rh- mother "Attack" an Rh+ fetus' red blood cells, leading to hemolysis. You want to quickly counsel the expecting couple abou tthe likelihood future offspring will face the same difficulty (any Rh+ fetus carried by this mother is likely to have this disease). The antigen is inherited in autosomal dominant fashion, so you know the mother is homozygous for the genes that make her Rh- (she lacks D antigen). The father knows he is Rh+ (he has D antigen) so you are able to advise them that on average.

A. none of their future offspring are likely to suffer form this dieases
B. 50% of their future future offspring are likely to suffer form this diseae
C. all future offspring are likely to suffer from this disease
D. because they have already had one affected child, the next will not suffer from this disease.
E. with the information given you cannot determine the likelihood of this disease for their future offspring

HINT - do not pay much attention to the disease (erythroblastosis fetalis); this is a problem of genotypes and phenotypes of mother, father, and offspring.

E. with the information given you cannot determine the likelihood of this disease for their future offspring

(Bill. You can't determine the other answers without knowing dad's genotype, right?)

28

You are treating a case of erythroblastosis fetalis, a disease of the fetus in pregnancy. This is most often caused by isoimmune reation to the D antigen, which is one of the antigens responsible for the Rh blood group. ANtibodies developed in an Rh- mother "Attack" an Rh+ fetus' red blood cells, leading to hemolysis. You want to quickly counsel the expecting couple abou tthe likelihood future offspring will face the same difficulty (any Rh+ fetus carried by this mother is likely to have this disease). THe antigen is inherited in autosomal dominant fashion, so you know the mother is homozygous for the genes that make her Rh- (she lakes D antigen). The father knows he is Rh+ (he has D antigen). If you then ask the father if he has previously fathered an Rh- child and he says YES, you are able to advise them that on average....

A. none fo their future offspring are likely to
B. 50% of their future future offspring are likely to suffer from this disease
C.all future offspring are likely to suffer form this disease
D. because they have already had one affected child, the next will not suffer form this disease.
E. with the information given you cannot determine the likelihood of this disease for their future offspring.

...

29

You are treating a case of erythroblastosis fetalis, a disease of the fetus in pregnancy. This is most often caused by isoimmune reation to the D antigen, which is one of the antigens responsible for the Rh blood group. ANtibodies developed in an Rh- mother "Attack" an Rh+ fetus' red blood cells, leading to hemolysis. You want to quickly counsel the expecting couple abou tthe likelihood future offspring will face the same difficulty (any Rh+ fetus carried by this mother is likely to have this disease). THe antigen is inherited in autosomal dominant fashion, so you know the mother is homozygous for the genes that make her Rh- (she lakes D antigen). The father knows he is Rh+ (he has D antigen). If you then ask the father if he has previously fathered an Rh- child and he says NO, you are able to advise them that on average....

A. none fo their future offspring are likely to
B. 50% of their future future offspring are likely to suffer from this disease
C.all future offspring are likely to suffer form this disease
D. because they have already had one affected child, the next will not suffer form this disease.
E. with the information given you cannot determine the likelihood of this disease for their future offspring.

...