single gene inheritance Flashcards
What is Mendelian inheritance?
Mendelian inheritance refers to the inheritance of traits determined by a single gene, and it can occur in all diploid organisms. Model organisms include S. cerevisiae, Drosophila, and Mus musculus.
Why is it difficult to observe Mendelian inheritance of single genes in humans?
It is difficult because human family sizes are usually small, making it harder to track the inheritance of single-gene traits.
What is the phenotype in a pedigree related to single-gene inheritance?
In a pedigree, phenotypes are usually the presence or absence of a disorder. Genetic diseases tend to be rare.
What is a test cross, and why is it used?
A test cross is used to determine an unknown genotype by crossing the organism with a homozygous recessive individual. The resulting offspring are analyzed using a Punnett square.
What is an example of autosomal dominant inheritance?
Marfan syndrome is an example of autosomal dominant inheritance. It affects fibrous connective tissues in the skeleton, eyes, cardiovascular system, lungs, and nervous system. Affected individuals have a defect in the fibrillin gene on chromosome 15.
What are the signs of autosomal dominant inheritance in a pedigree?
Affected individuals appear in all generations.
Both sexes are affected.
Only one copy of the abnormal gene is required for the trait to be expressed.
What are the four model ways of single-gene inheritance?
Autosomal dominant.
Autosomal recessive.
Sex-linked dominant.
Sex-linked recessive.
What are the signs of autosomal recessive inheritance in a pedigree?
Most generations are unaffected.
Both sexes are affected.
Parents are heterozygous carriers.
: What does X-linked recessive inheritance look like in a Punnett square?
: In X-linked recessive inheritance, the trait is located on the X chromosome. A difference in male and female offspring in the F2 generation indicates X-linked inheritance.
What are the features of sex-linked dominant inheritance?
The trait appears in all generations.
Affected fathers pass the condition to all daughters.
Affected heterozygous mothers can pass the condition to both sons and daughters.
Why do males always express X-linked recessive traits?
: Males only have one X chromosome, so if they inherit the recessive trait, they will always display it since they lack a second X chromosome to potentially mask it.
What are the characteristics of sex-linked recessive inheritance?
The trait appears to skip generations.
Mostly males are affected.
Females can be heterozygous carriers.
genetic trait
a characteristic of an organism
phenotype
observable traits of an organism
allele
a variation of the same gene
