Ch 12 Card DECK Flashcards
What is the difference between a character and a trait?
A heritable feature is called a character and a variant of the trait is called a trait. For example, color is a character, purple is a trait.
What does it mean to be true breeding?
Generations of offspring have the same trait. For example, if the parental generation has curly wings, so will the F1, F2, F… generation. F stands for filial.
What is a gene?
A section of DNA that codes for a protein.
or you can say
A section of a chromosome that codes for a protein.
What is an allele and what accounts for their differences?
Alternative versions of a gene. Alleles differ in their DNA sequence of AGCT’s.
Define the Law of Segregation
Alleles of a particular gene end up in different gametes.
What is a chromosomal locus?
A specific location on the DNA.
What is the difference between genotype and phenotype?
Genotype represents the genetic makeup of the organism.
Phenotype is an observable trait.
What is the value of a testcross and how do you perform one?
A testcross reveals the genotype of an organism for a specific trait. Breed two individuals, one of which is homozygous recessive for the trait. If all of the offspring express the dominant trait then the parent in question is most likely homozygous dominant.
AA x aa = Aa (and the dominant trait is always expressed)
vs
Aa x aa = AA + Aa + aa
State the Law of Independent Assortment. What assumptions lead to the Law of Independent Assortment?
Genes are distributed into gametes independently of one another.
This assumes: the genes are not on homologous chromosomes or, if they are on the same chromosome, they are far apart enough from each other where the probability of having a crossover event assures independence.
What does the multiplication rule of probability state?
The multiplication rule states that the probability that two or more independent events will occur together is the product of their individual probabilities. For example, if the chance of aa is 1/4 and the chance of bb is 1/2, the chance of aa AND bb is 1/4 * 1/2.
What does the addition rule of probability state?
The addition rule states that the probability that any one of two or more mutually exclusive events will occur is calculated by adding together their individual probabilities. For example, if the chance of having Aa is 1/4 and the chance of having aa is 1/2, the probability of having at least one recessive trait is 1/4 + 1/2.
What is the difference between dominance, codominance, and incomplete dominance? Give an example of each.
Dominance - only one allele is seen in the phenotype
(Aa = AA)
Codominance - both alleles are seen in the phenotype
(AA x A’A’ = AA’)
Incomplete dominance - mixture of alleles
BB ≠ BW
Examples: dominance = height in peas incomplete = red X white = pink flower codominance = black cow X white cow = black and white cow
What does it mean for a gene to have multiple alleles (greater than 2)? Give an example.
A gene has more than two alleles and each allele codes for a different protein. Alleles: A/B/O/Rh.
NOTE: the AB and Rh antigens are membrane-bound carbohydrates but these carbohydrates are coded for by the proteins produced by the different alleles.
What is polygenic inheritance? Give an example.
The phenotype of a cell is determined by the additive effect of two or more genes. Eye color is determined by approximately 16 different genes.
Others? human height
Is phenotype determined only by genotype? Given an example.
No - the environment has an impact on phenotype. Example: artic hare is white in the winter and grey in the summer. This is an adaptation.
