Chapter 12 - Mendel, Genes, & Inheritance Flashcards
Genotype
an organism’s DNA, genes, & alleles
Phenotype
how the organism’s DNA is visually expressed
-determined by the genotype
Homozygous
2 of the same allele
Heterozygous
1 dominant allele & 1 recessive allele
F1 Generation
the first generation of offspring from a cross between 2 true-breeding parents
Monohybrid
cross in which 2 different true-breeding parents for 1 trait produce offspring
Dihybrid
cross in which the parents both have 2 experimental traits
What is being segregated in the Principle of Segregation?
different alleles separate when homologous chromosomes separate during anaphase I
What evidence supports the Principle of Segregation?
each gamete produced during meiosis exhibits 1 of each gene
When do you use the product rule?
in the presence of the word “and”
-when 2 events happen independently of each other
When do you use the sum rule?
in the presence of the word “or”
-when there are 2 or more ways through which to obtain the same outcome
Testcross
a method to determine the genotype of an individual with a dominant phenotype but an unknown genotype
-the individual is crosses with homozygous recessive individual
In a testcross, how would I know if the individual is homozygous dominant?
if the all of the offspring are dominant
In a testcross, how would I know if the individual is heterozygous?
if some of the offspring are recessive
What is being assorted in Mendel’s Principle of Independent Assortment?
individual genes –> genes are present on separate chromosomes
What evidence supports Mendel’s Principle of Independent Assortment?
some of the offspring that form are recombinants of their parents –> they have a different combination of the 2 genes that were studied
How does the Principle of Independent Assortment relate to meiosis?
genes are able to be inherited independently because homologous chromosomes & sister chromatids are are separated during meiosis
How does the Principle of Segregation relate to meiosis?
the alleles that are separated are done so during anaphase I of meiosis I
Incomplete dominance
mating parents that are true-breeding for 2 different traits create offspring that are a blend of the 2 traits –> the allele of a gene is not completely dominant over another allele for the same gene
Codominance
two alleles that affect phenotype are both expressed –> alleles have approximately equal effects in individuals, making them equally detectable
-Ex: blood types
Epistasis
2 or more genes interact in order to form a specific phenotype –> alleles of a gene at one locus inhibit or mask the effects of alleles of a different gene at a different locus
-Ex: Labrador coat colors –> dogs will always appear yellow if they have a particular allele for a gene that will overpower any other allele for a different gene
Pleiotropy
a single gene affects more than one character of an organism
-Ex: sickle cell disease –> the single mutated hemoglobin affects numerous other functions of the body
Polygenic inheritance
many genes contribute to a single phenotype
-height
Dihybrid cross phenotypic ratio
9:3:3:1
Monohybrid cross phenotypic ratio
3:1
