Ch 22 Medical Genetics Flashcards
What are human traits determined by?
Both genetics and the enviroment
Are diseases more likely in genetic relatives or in the general population?
Genetic relatives
What is a monozygote?
An identical twin
What is a dizygote?
A non identical twin
Is a disease more likely to occur in momzygotes or dizygotes?
Monozygotes
what is concordance?
The degree to which a disease is inherited. Calculated by dividing number of twins BOTH with disease over number of twins in which ONE has disease
What is the concordance in diseases that are only associated with a single gene in idnetical twins?
100%
What is concordance in dizygotic twins assuming one is HETEROYGOUS?
50%
What is concordance for recessive diseases in twins?
25% assuming both heterozygous
What are reasons that concordance would be lower than expected?
If incomplete penetrance occurs OR if one twin gets disease from mutation after fertilization
Examples of Autosomal Recessive Disorders
Ablinism, ADD, and Cystic Fibrosis, Tay Sachs disease
Characteristics of Recessive diseases
1) Affected offspring usually has two unaffected parents
2) two unaffected parents (heterozygotes) have 25% diseased children
3) Two affected individuals produce affected offspring
Does gender affect recessive disease frequency?
NO equal in both genders
Examples of Autosomal Dominant Disorders?
Huntingtons disease and Dwarfism
Characteristics of Huntigntons?
1) affected offspring have one or more affected parents
2) Homo more effected that hetero individual
Examples of Xlinked recessive diseases?
Hemophila A/B and muscular distrophy
What are biochemical Assays used for?
To determine the enzymatic function of certain proteins that effect diseases
Ex: Hex A (enyzme that causes tay sachs
What is Amniocentesis?
removal of amniotic fluid from embyo for karyotyping
What is chorionic villus sampling
removal of small pieces of chorian (placenta)that are analyzed. Can be done earlier but poses greater risk for miscarriage
What is preimplantation genetic diagnosis?
Conducted before pregnancy in vitro. Genetic testing of embryo by removing one of the two cells at 8 cell stage. Called embryo biopsyor blastomere biopsy
What is a prion? And who does it effect?
proteinaceous infectious particles that alter protein function post-translationally.
Causes nerodegenerative diseases in cows
What do pRp proteins bind to?
Copper ions with high affinity
What are the two prion conformations?
Normal PRPc and abnormal PRPsc
How is the abnormal form of PRP attained?
By eating bad meat or by being infected by individual with PRPsc or by spontaneous transformation
Why is PRPsc so bad?
Because the prescence of the abnormal PRP causes normal PRPc to convert to PRPsc
Cancer caused by what?
Uncontrolled cell division
Carinogen
Enviromental causes of cancers
Characteristics of Cancer include?
1) usually originates in single cell
2) usually starts with benign growth
3) progresses to malignant over time
4) invasive and metastatic
How can viruses cause cancer?
Carry viral oncogenes into the cell
Transformation
Process of changing normal cell to malignant cell
What are ACV’s?
Type of virus capable of transformation
What is a gene that promotes cancer called?
An oncogene
The normal cell cycle is regulated by what?
polypeptide hormones known as growth factors
Proto Oncogene
Normal gene with capability of becoming oncogene
How do proto oncogenes become oncogenes?
1) Amount of encoded protein greatly increased
2) protein structure altered resulting in overexpresion
3) Protein expressed in cell type where it is not normally expressed
What is the RAS protein?
A GTPase that converts GTP to GDP+pi
What is the effect of RAS becoming an oncogene?
1) decrease ability of RAS to transform GTP
2) Increase the rate of exchang of bound GDP for GTP
* BOth result in more bound GDP keeping signaling pathway turned ON and cell division increasing
How to change proto oncogene to a full blown oncogene?
1) Missense mutation causes abnormal function
2) Amplification
3) Viral Integration
4) Chromosomal Translocation
What do tumor supressor genes do?
prevent proliferation of cancer. If inactivated by mutation, chances of cancer increase
What is p53 gene?
A tumor supressor gene that senses DNA damage
* 50% of cancers associated with mutation in this gene
What are the three things p53 does?
1) repair cell damage
2) start apoptosiis of bad cells
3) arresting cell cycle
How does apoptosis work?
protease called capspaces act as exuctioners of cells by digesting things like microtubles
How is maintenance of the genome accomplished?
Checkpoint proteins and DNA repair proteins
How do checkpoint proteins work?
prevent cell division when damaged DNA is detected
Prevent accumulation of cyclin CDK complexes that promote cell division
What do G1 and G2 checkpoints do?
look for DNA damage and if found prevent formation of cyclin cdk complexes
What does M checkpoint do?
sense if a chromosome is not attached to spindle correctly
