Genetics Chapter 6

The ability to roll the tongue is caused by a dominant allele. A woman is a "roller," but one of her parents is not. The woman is expecting a child with a man who is a "nonroller." What is the probability that their first child will be a "roller"?

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What are the trends of X-linked recessive traits?

An affected males does not pass the traits to his sons but can pass the allele to a daughter who is unaffected which then passes it to sons who are. X-linked recessive traits appear more frequently in males. Only sons of affected or carrier female will be affected.

What are the major assumptions associated with X-linked dominant trait?

Appears in both males and females; often more in females DOESN'T SKIP GENERATIONS Suspect if only daughters of an affected father are affected Rule out X-linked recessive if any affected daughters are born to affected mothers and non-affected fathers.

What are the major assumptions associated with autosomal dominant traits?

Equal number of affected males and females, and both sexes transmit trait Affected individual has at least one affected parent Trait appears in every generation Unaffected parents do not transmit trait

What is a Pedigree?

Family tree that outlines the inheritance of one of more characteristics.

What are the major assumptions associated to X-linked recessive traits?

It is suspect if more males affected Affected sons usually born to unaffected mothers, so CAN SKIP A GENERATION Never passed from father to son Rule out X-linked dominant if any daughters of affected father don't have disease

What are the major assumptions related to autosomal recessive traits?

New carriers may marry into the family. Equal number of affected males and females. Affected individuals often born to unaffected parents. Look for skipped generations. For rare recessive alleles, new carries marrying into the family is uncommon. Higher possibility of trait appearing, however, if inbreeding

What is a Proband?

Person from whom the pedigree is initiated.

What are the major assumptions when solving Pedigree problems?

Unrelated individuals marrying into the family are homozygous for the wild-type. Dominant mutations are usually lethal when homozygous When determining the mode of inheritance in a pedigree, be sure to rule out other possibilities.

What are the major trends associated with X-linked dominant trait?

X-linked dominant traits do not skip generations. Affected males pass the trait to all their daughters and none of their sons. Affected females ( if heterozygous) pass the trait on to about half of their sons and about half of their daughters. All affected males have an affected mother.

What are the major trends of Y-linked traits?

Y-linked traits appears only in males. All male offspring of an affected male are affected. All males descendants of an affected male will be affected.

What characteristic would you NOT expect to see in a pedigree of an X-linked recessive trait? a)The trait is more commonly seen in males b)The trait can skip a generation c)The trait is commonly passed from fathers to sons d)Whenever a daughter receives a trait, the father is affected e)An affected son's mother either has the trait or is heterozygous (carrier)

c) The trait is commonly passed from fathers to sons

A pedigree of an autosomal dominant trait, such as familial hypercholesterolemia, will likely show all of the following characteristics EXCEPT: a) actually all of these are expected b)equal number of males and females affected c) skipping a generation by the trait d)on average, half of the offspring of carriers will have the trait. e)affected individuals born to unaffected parents

c) skipping a generation by the trait

What is another characteristic you expect to see in a pedigree of an Y-linked trait? a) The trait is more commonly seen in females b) The trait does not skip a generation c)The trait is commonly passed from fathers to daughters d)The trait is often recessive e)An affected son's mother either has the trait or is heterozygous (carrier)

c)The trait is commonly passed from fathers to daughters

A pedigree that demonstrates an autosomal recessive trait, such as Tay-Sachs disease, will likely show all of the following characteristics EXCEPT: a) actually all of these are expected b)equal number of males and females affected c) skipping a generation by the trait d)on average, half of the offspring of carriers will have the trait. e)affected individuals born to unaffected parents

d) on average, half the offspring of carriers will have the trait.

If a trait is passed from a father to both of his daughters, but not to his son, it can be concluded that a) the gene is X-linked dominant b) the gene is X-linked recessive c)the gene is autosomal dominant d)the gene is autosomal recessive e)none of these can be concluded

e) none of these can be concluded

In pedigree analysis, the proband is

the individual with the trait or disorder from whom the pedigree is initiated.

What are the trends of autosomal dominant traits?

Autosomal dominant traits appear equally in males and females. Unaffected persons do not transmit the trait, and affected persons have at least one affected parent. Trait appears in every generation.

What are the 5 basic types of inheritance patterns?

Autosomal recessive Autosomal dominant Sex-linked recessive Sex-linked dominant Y-linked (Holandric) inheritance

What are the trends of autosomal recessive traits?

Autosomal recessive traits usually appear equally in males and females and tend to skip generations. Autosomal recessive traits are more likely to appear among progeny of related parents.

What are the major complications regarding human genetic studies?

Controlled matings are unethical, long generation time, and small number of offspring conceals probability patterns

What is assumed in basic pedigree trees?

Full Penetrance and other factors affecting phenotype are ignored.

What is a classic example of a X-linked recessive trait?

Hemophilia inherited as an X-linked recessive trait in the European royal families.

What are the major assumptions associated with Y-linked traits?

Suspect if all males born to affected fathers are affected also Only males affected