Genetics Flashcards
What is Mendels second law?
The law of independent assortment-each genes inheritance (assortment) is independent of the inheritance of other unlinked genes in a dihybrid cross.
What are the 4 tenets of Mendel’s first law?
- Genes exist in alternative forms as alleles.
- 2 alleles for each gene, one from each parent
- 2 alleles segregate during meiosis, giving gametes that carry only one allele for any inherited trait.
- With there are two different alleles in an organism, only the dominant will be expressed while the silent is recessive
How could you calculate the likelihood of a genotype in the progeny?
By multiplying the probability that one parent donated a specific gamete and the other donated a specific gamete.
Cells are ______ after meiosis I?
Haploid-homologous pairs of chromosomes line up and separate (AKA INDEPENDENT ASSORTMENT), although their sister chromatids remain attached until meiosis II.
In what case of genetic linkage (tight/weak) would we see no recombinant phenotypes?
Tight and complete-if genes are located on the same chromosome, they tend to segregate together. Recombine at 0 percent frequency
Weak-recombine at 50 percent frequency, the percentage expected from independent assortment.
What is crossing over and what does it result in?
A process that leads to recombination by physical exchange if DNA between homophobia chromosomes. This results in genes that were initially linked to become unlinked.
How does a distance between genes play a role in recombination?
The further apart two genes are, the more likely there will be recombination
What is incomplete dominance?
The resulting phenotype is a mixture of the two parental phenotypes (ie: red + white = pink)
What is codominance?
The phenotype is complete expression of both dominant phenotypes. There must be multiple coding alleles for a gene, and more than one of these alleles must be dominant. (Blood type)
What is the penetrance of a genotype?
of individuals in a population CARRYING the allele WHO EXPRESS the phenotype. (Ie: huntingtons disease-highly penetrant because 95% of people with the affected allele will exhibit the symptoms).
What is gene expressivity?
The varying expression of disease symptoms despite identical genotypes.
Is huntingtons disease dominant or recessive?
Dominant and late acting-lethality doesn’t occur until after reproduction
Is cistic fibrosis dominant or recessive?
Lethal recessive, meaning we see the full effects before the child is able to reproduce
If it’s not sex-linked, it is…
Autosomal
If an X chromosome has a mutation and is inherited by the male, the male is affected and considered…
Hemizygous
In a pedigree, males are represented by ____ and females are represented by ____.
squares and circles
In a pedigree, affected individuals are _____
Shaded
In a pedigree, female carriers of a sex linked trait are….
Half shaded
Any variation from the common diploid number of 46 is considered _____ and is most commonly caused by_____.
Aneuploidy and non disjunction
Trisomy is
Extra 21st chromosome (2n +1) ie: trisomy 21
Monosomy is
2n-1
Females born with a single X chromosome are known as…
Turner syndrome females (XO)-short in stature, sterile, few to no female secondary sex characteristics
XXX Females are
Super females
XXY males are
Talk male with breasts and I descended testes and are sterile
