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Terms in this set (34)
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.
They are different based on their fingerprints and Type I diabetes tendancy
How many chromosomes are there? How many are X, and how many are Y? How many are autosomes, and what is an autosome?
Including the sex chromosomes there are 23 pairs
Male has one X and one Y, female has 2 X
22 autosomes= the non-sex chromosomes
Name 4 Trisomies for which a live birth is possible.
Which produces mild to undetectable symptoms?
Trisomy 21, Trisomy 13, Trisomy 18, Trisomy X
Trisomy of which number chromosome is Down Syndrome?
What is XYY Syndrome? Can one bare children?
Born with an extra Y Chromosome- tall can bear children
-It was thought that these individuals were more likely to be institutionalized in prison or mental home (may not be true)
What is Klinefelter Syndrome?
XXY chromosomes (extra X)
bear NO children, testicular failure, suffer diseases at the same rate as females (ex. breast cancer)
What is Turner Syndrome?
Unisomy X (one X)
-may have web-look on neck, short
-hormone therapy available to have children
4-How does inheritance of an X-linked disease differ from inheritance of an autosomal disease?
Autosomal Inheritance is non-gender dependent because it occurs on non-sex chromosomes, while X-linked diseases are gender dependent
How does inheritance of a mitochondrial disease differ from inheritance of an autosomal disease?
This is strictly maternal inheritance
5-Which will probably have the greatest number of
offspring who suffer from an inherited disease
(may be more than one)?
Parents both heterozygous for an autosomal dominant disease
What is penetrance?
How might penetrance mean that no individuals with the disease symptoms are observed in a specific pedigree?
Penetrance is a measurement of the proportion of individuals in a population who carry a disease-causing allele and express the disease phenotype.
There are cases known as incomplete penetrance where the individual will have the disease mutation but not show any symptoms of the disease due to modifier genes, environmental factors, etc
Define genotype, phenotype, and how they differ.
How does this apply to penetrance?
Genotype- what the genes are
Phenotype- What is physically seen (ex. eye color)
The genotype will determine the phenotype
Although the genotype may display the mutation for the disease, the phenotype will not express this disease. So you have the gene but dont have the symptoms
What is Hereditary Hemochromatosis?
Disease of iron overload
most frequently seen inherited disease in the US
can cause oxidative damage
7-Environmental factors that affect the penetrance of hereditary hemochromatosis=
1. Dietary Iron (should be decreased)
2. Blood donation will help
3. Gender- females lose more blood= helps them
4. Alcohol use- increases iron uptake= even more iron
8-Why does a X linked disease like Duchennes muscular dystrophy seldom cause symptoms in females?
Females have a protective effect due to bystander effect. Since females have 2 X chromosomes, one of them will be inactivated. In the case that the bad gene is the one that remains active, there will be a bystander effect where the good cells (with good gene) on either side will take care of the defective cell.
If a genetic disease is discovered where the disease only occurs when the defect is inherited by the father, the gene is most likely ____
10-What is meant by a genetic disease that is never inherited?
A genetic disease that cannot be inherited is a defect in a gene found in only some cells. This happens because DNA is just a chemical and there are mutations that can arise at any time. Not inherited because not in all cells.
What disease is a genetic disease in which the mutations that cause it often occur after birth?
Cancer, there are pre-depositions but most is due to mutations after one is born.
13-Describe the genetic defect that results in Huntington disease. (What is there more of in terms of nucleotides?)
This is due to high penetrance, autosomal dominant, triplet nucleotide expand. Expansion is CAG which codes glutamine, makes polymerase stutter.
This is monogenic
Screening: <35 CAGs = fine, > 36 CAGs will have disease, 35-36 is grey area
17- three examples of diseases mentioned in the handout that can be caused by a single gene defect (monogenic) or by the combined effect of many genes (polygenic).
Hypertension, cardiovascular disease and Type 2 Diabetes
What diseases are only polygenic?
Neural tube defects, developmental defects (cleft lip), asthma, alcoholism, bipolar, epilepsy, obesity, Type 1 diabetes
19- What are the class of genes that have been found to be associated with a monogenic disease that may be thought of as type 2 diabetes?
Name a class of genes that has been found to be
associated with type 1 diabete
3 HLA genes
What is the gene that has been found to be associated with the development of polygenic type 2 diabetes?
PPAR gamma gene
One form of this type 2 diabetes gene is found in 85% of the world population. Is this prevalent form protective against, or predisposing to developing diabetes?
The protective form is found in 15%, 85% have the form that is associated with type 2 diabetes
20-Which infectious disease(s) is NOT thought to be protected against by an inherited genetic mutation or deletion?
Smallpox, anthrax, leprosy
For each of these diseases that there is inherited protection against, name the gene in which mutation is thought to be protective:
via cystic fibrosis, no CFTR protein receptor for typhoid to enter
via sickle cell anemia due to lack or deformity of RBCs where Malaria reproduces
21-What is a "snip?" What is the frequency of an
SNP in human DNA?
single nucleotide polymorphisms
24-autosomal dominant homozygote
autosomal dominant heterozygote
Which get disease?
X-linked recessive hemizygous
X-linked recessive heterozygote
X-linked recessive homozygote
Mitochondrial, only father has disease
Mitochondrial, only mother has disease
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