Week 2- transmission genetics and pedigree analysis Flashcards
What does polygenic mean?
It is where traits are controlled by more than one gene.
what is a carrier?
A heterozygous individual that carries the allele for a genetic disorder but is unaffected.
The child however becomes affected if both the parents are heterozygous and carry the allele for a RECESSIVE genetic disorder.
Known as autosomal recessive
What is an autosomal dominant pattern?
This is where the parents are affected by a genetic disease but the child is unaffected
How does a faulty gene trigger disease?
When a gene mutates, the protein encoded by the gene will also be mutated/abnormal. This can disable the enzyme which can halt reactions/processes in the body.
What is a pedigree analysis?
Information on the presence/absence of a phenotypic trait is collected from as many people in the family across generations.
This allows the geneticist to estimate the probability a child may inherit a genetic disorder.
What are the 4 types of hereditary genetic disease?
Autosomal dominant - affected children have at least one affected parent. Heterozygotes are affected.
autosomal recessive - affected children can have both unaffected parents. Heterozygotes show a normal phenotype.
x - linked dominant - this is where the daughters inherit disease from their affected father.
x - linked recessive - this is where the sons inherit disease from their carrier mothers (carrier mothers are daughters of a male with an X linked disorder) daughters are less likely to have it as they have an extra X chromosome
Check diagram on slide 9
What is a Y linked trait?
This is passed from an affected father to sons and is expressed phenotypically
What is epistasis?
This where one pair of alleles masks the phenotypic expression of another.
For example, you can have the gene for blonde hair, but if you have the gene for baldness, you can’t see the blonde hair. The baldness gene is epistatic and masks the gene for blonde hair.
Labradors as an example!!
What is pleiotropy?
where genes affect more than one trait.
What is recessive epistasis?
Where the recessive allele overshadows the other gene
Labrador example!
When will the inheritance of characters by a single gene not follow mendelian patterns?
- When alleles are not completely dominant or recessive
- When a gene has more than two alleles
- When a gene produces multiple phenotypes
What is complete dominance?
When the phenotypes of the dominant homozygotes are identical
What is incomplete dominance?
Where the phenotypes of the F1 generation hybrids is between the phenotypes of the two parental varieties.
What is codominance?
Where two dominant alleles affect the phenotype in separate, distinguishable ways.
eg: LM LN, CR CW
How is the ABO phenotype for blood group determined?
You can determine this by mixing the patients blood with anti A or anti B antibodies.
If a particular antigen is present on the RBC, it will react with the antibody causing agglutination.
