11.3 Study Guide Flashcards
What does autosomal dominant mean?
A genetic condition can be passed down from one parent to a child if the child only inherits one copy of the mutated gene from that parent.
What does autosomal recessive mean?
A genetic condition will only appear if an individual inherits two copies of the mutated gene, one from each parent.
What does sex-linked dominant mean?
A trait is caused by a gene on the X-chromosome, and only one copy of the mutated gene is needed to give the males or females the trait.
What does sex-linked recessive mean?
A genetic condition where the gene causing the disorder is on one of the sex chromosomes (X or Y) and is recessive.
What is a carrier?
Heterozygotes are carriers. They have a “normal phenotype” because one normal allele produces enough of the properly functioning proteins.
What is X-inactivation?
Female mammals inherit 2 X-chromosomes. Which X becomes a Barr body is random. Ex: Patchwork trait= “mosaic”
What does pedigree mean?
A recorded ancestry of animals through generations.
What are the important similarities and differences between different modes of inheritance: autosomal dominant, autosomal recessive, sex-linked recessive, sex-linked dominant?
In autosomal dominant, a single copy of a mutated gene from one parent is enough to cause the disorder. However, in autosomal recessive, both copies of the gene must be mutated (one from each parent) to express the disorder. In both autosomal dominant and recessive, the gene is located on one of the autosomes, meaning that males and females are equally likely to be affected.
In sex-linked dominant, a single copy of a mutated gene on the X chromosome is enough to pass the trait on to both males and females. In contrast, sex-linked recessive traits require two copies of the mutated gene (one on each X chromosome) to pass on the trait to females, while males, with only one X chromosome, the trait can be passed on by a single copy. in both sex-linked dominant and recessive inheritance, the genes are located on sex chromosomes (X or Y), leading to unique inheritance patterns between males and females.
What is the difference between gain of function vs. loss of function mutations?
Dominant diseases result in a “gain of function”. The mutated allele codes for a protein that does something that it’s not supposed to. Having just one allele causes a new disease phenotype.
Recessive diseases result in a “loss of function”. A recessive protein often codes for a malfunctioning protein or no protein at all.
Explain an example of a cross involving a sex-linked trait.
Drosophila breeding:
True breeding red-eye female x True breeding white eye male
F1: 100% red eye offspring
F2: 100% Red eye female and 50% red eye male, 50% white eye male
How do you rule out different modes of inheritance on a pedigree and assign genotypes to individuals on a pedigree?
If the trait skips a generation, then it cannot be dominant and must be recessive. If affected parents have an unaffected child, then it cannot be recessive. If more males than females are affected, mothers have only infected sons, and daughters have infected fathers, then it is likely only sex-linked recessive. If there are two affected parents, the offspring cannot be recessive because the parents could not have an unaffected offspring. They parents must be heterozygous. In autosomal recessive, the offspring of two unaffected parents cannot be dominant. 100% incidence of affected daughters from an affected father indicates sex-linked dominant. 100% incidence of affected sons from an affected mother indicates sex-linked recessive. If there are unaffected parents with an affected child, then you can rule out dominant. If there are affected parents with an unaffected child, then you can rule out recessive.
If there are more males than females, affected females with affected fathers, and affected mothers with all affected sons, then it is likely sex-linked recessive. If affected males have all affected daughters, then it is likely sex-linked dominant.
