Genetics - Campbell Flashcards
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.
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).
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)
Trisomy of which number chromosome is called Down syndrome?
21
What is XYY Syndrome?
A mild syndrome that results in a male having an extra Y chromosome. Mild, tall, can bear children.
Trisomy of which number chromosome is Klinefelter Syndrome? What are the affects?
XXY; Results in testicular failure.
What is Turner Syndrome?
A variable disease with only one X chromosome (As to the normal XX or XY)
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.
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).
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
……….
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.
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.
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.
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
What disease is a genetic disease in which the mutations that cause it often occur AFTER birth (discussed further in lecture)?
Proteus Syndrome.
