Inheritance Flashcards
Allele
Different version of the same gene
Genotype
Combination of alleles
Homozygous
Two of the same allele
Phenotype
Physical/observable trait
Dominant
An allele that is expressed in the phenotype
Phenotypic plasticity
Reversible changes in phenotype due to the change in patterns in gene expression
Recessive
Allele that is only expressed in the phenotype when the dominant allele is absent
Sex linked gene
Located on the sex chromosome
Incomplete dominance
Located on the autosome
Neither allele is completely dominant over another, resulting in a blended phenotype in a heterozygous individual
Codominance
Two allel for a particular that are both expressed equally in the phenotype of an organism
Autosomal dominant(pedgree)
-One of the parents must have the disease
-not all the kids will have the dises
-it cannot skip generations
Autosomal recessive(pedigree)
-Both parent=kids will all have it
-Kids have it does not equal parents have it
-generations can be skiped
X-inked recessive(pedigree)
-For a girl to have dad must have
-If mom has it=son has it
-Most common in males
Mendel’s Laws of Inheritance:
1. Law of Segregation
Each organism has two alleles per trait (one from each parent).
During gamete formation (meiosis I, anaphase I), these alleles separate, so each gamete carries only one allele.
Mendel’s Laws of Inheritance:
2. Law of Independent Assortment
Genes for different traits separate independently during gamete formation.
Applies to genes on different chromosomes or those far apart on the same chromosome (unless linked).
Mendel’s Laws of Inheritance:
3. Law of Dominance
Dominant alleles mask recessive ones in heterozygous individuals.
Example: Tt (T = Tall, t = short) → Plant will be Tall because T is dominant.
Locus
Specific location of a gene
Discrete Variation
Traits controlled by one gene with a limited number of phenotypes (e.g., ABO blood groups).
Continuous Variation
Traits are influenced by multiple genes, creating a range of phenotypes (e.g., height, skin color).
ABO Blood Groups
The ABO blood group system is determined by multiple alleles and codominance, leading to four possible blood types: A, B, AB, and O.
Dihybrid crosses
hetro x hetro- 9:3:3:1
Hetro x homo-1:1:1:1
Alleles & Antigens
Iᴬ → Produces Type A antigens.
Iᴮ → Produces Type B antigens.
i → No antigens (Type O).
Genotypes & Corresponding Blood Types
ᴬIᴬ or Iᴬi → Type A blood (A antigens).
IᴮIᴮ or Iᴮi → Type B blood (B antigens).
IᴬIᴮ → Type AB blood (Both A & B antigens, codominance).
ii → Type O blood (No antigens).
Codominance in Blood Groups
IᴬIᴮ individuals express both A & B antigens, showing codominance—neither allele is dominant over the other.
Linked Gene
Genes located on the same chromosome where it is inherited together unless recombination occurs
Recombinant
New combination of alleles on a chromosome as the result of crossing over
