Top5-Ch6-P135-146Reverse Flashcards
- Hutchinson-Gilford Progeria Syndrome (HGPS) causes premature aging
- About 50 patients worldwide
- Fatal by about 13 years of age due to age related organ failure (often coronary problems)
- Dominant autosomal inheritance pattern (usually)
- Caused by mutation in the lamin A (LMNA) gene
Explain HGPS
- pedigrees
- twin studies
- adoption studies
genotype and environment
prudently
Study of human inheritance needs three special tools. What are they?
Most phenotypic traits are influenced by both ____ and ______. Difficult to separate the two. Results must be interpreted ______.
- controlled matings not possible
- long generation time
- small numbers of offspring
What are three difficulties with human genetic study, even though much is know about human anatomy, physiology and biochemistry
a pictorial representation of a family history, essentially a family tree that outlines the inheritance of one or more characteristics.
See chart attached with symbols used in pedigrees.
What is a pedigree?
- Equal frequency in males and females
- Affected children born from unaffected parents
- Trait seems to skip generations. Only if two parents have it is there chance of 1/4 children getting it.
- More often found in offspring from consanguine matings (mating between closely related people) because there is greater chance of both parents having the recessive allele.
- Affected parents produce affected offspring
- Example: Tay Sachs disease
See chart below of pedigree for this with first cousins marrying to increase likelihood of it being passed on.
Explain Autosomal Recessive Traits
- Equal frequency in males and females
- Affected children have an affected parent (unless they carry new mutation, very rare, or unless there is reduced penetrance)
- Trait does not skip generations
- Unaffected persons do not transmit the trait provided that it is fully penetrant.
- Examples: Familial Hypercholesteremia (high cholestorol levels), Waardenburg Syndrome (deafness, fair skin, visual problems and a white forelock)
See attached pedigree analysis
Explain Autosomal Dominant Traits
Pedigree for Waardenburg syndrome (Autosomal Dominant Trait). See table.
- More often in males than females
- Not transmitted from father to son because Y is passed from father to son.
- Affected sons usually born to unaffected mothers
- Tend to skip generations
- Example: Haemophilia A, is absence of protein necessary for blood to clot.
Explain X-Linked Recessive Traits
- Affect both males than females
- Affected males have affected mothers (unless new mutation, very rare)
- Affected males transmit the trait to their daughters
- Example: Hypophosphatemia or familial vitamin-D resistant rickets - people with this disease have symptons that appear like rickets like deformities, stiff joints etc.
Explain X-Linked Dominant Traits
- Appear only in males
- Affected fathers transmit the trait to their sons
- Does not skip generations
- Example: maleness
Explain Y-Linked Traits
Pedigree characteristics of autosomal recessive, autosomal dominant, X-linked recessive, X-linked dominant and Y-linked traits. See table on next page.
nonidentical twins. Have 50% of their genes in common (as non twin siblings), fertisilised by two different sperm and two separate eggs. Dizygotic twinning tends to run in families and is influenced by hereditary.
Dizygotic twins are?
identical twins and have 100% of their genes in common. There appears to be little genetic tendency for producing monozygotic twins.
Monozygotic twins are
environment
Comparisons of mono- and dizygotic twins can separate the influence of ________ in a certain trait
when both members of a twin pair have a trait the twins are said to be concordant. If only one member of the pair has the trait the twins are said to be discordant.
Concordance is the percentage of twin pairs that are concordant for a trait.
Concordance is?
- genetic
- environmental
Higher concordance for monozygotic twins compared with that for dizygotic twins indicates that ______ factors play a role in determining differences in a trait. Low concordance for monozygotic twins indicates that _______ factors play a significant role.
the genetics of asthma showed that genes are an important factor but environment plays an important role as well
In twin studies for asthma it showed …?
- genes
- environment
- Genetic research into obesity is done more and more
- 1994, leptin gene was isolated
- Genetic control of bodyweight is very complex
Twin studies used to study the genetics of obesity showed that _____ are an important factor but _______ plays an important role as well.
- genes and environment
- environment
- genetic
- no
- Adoption studies are a very powerful technique for separating influences of ______ and _____ on a certain trait
- If adopted children show similarities in a characteristic to their adopted parents, the trait is mainly affected by ________
- If, on the other hand adopted persons and their biological parents show similarities, these similarities are likely to be due to _____ factors.
- Adopted children have __ genes in common with their adoptive parents
- Obesity, but genetics was not the only factor
- A strong genetic influence was also shown in alcoholism. Again, genetic factor was necessary but not always enough.
- Also show that schizophrenia has a genetic basis
See obesity chart below.
In adoption studies it has been shown that three major disorders are influenced by genetics. Name them.
