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What are true-breeding parents called in a genetic cross?
The P (parental) generation
What is the F1 generation?
The first filial generation, offspring of the P generation
What is the F2 generation?
The second filial generation, offspring of the F1 generation
What does Mendel’s law of segregation state?
Two alleles for each trait separate during gamete formation
What does the law of independent assortment state?
Each pair of alleles segregates independently during gamete formation
During what phase of meiosis does independent assortment occur?
Metaphase I
What are alternative versions of a gene called?
Alleles
How many alleles does each sexually reproducing organism inherit per gene?
Two (one from each parent)
What is a homozygous organism?
An organism with two identical alleles for a gene (RR or rr)
What is a heterozygous organism?
An organism with two different alleles for a gene (Rr)
What is a phenotype?
The physical expression of a trait
What is a genotype?
The genetic makeup of an organism
What is a testcross used for?
To determine if an organism showing a dominant trait is homozygous dominant (RR) or heterozygous (Rr)
What type of individual is used in a testcross?
A homozygous recessive (rr) individual
What is a monohybrid cross?
A cross that studies one trait
What is a dihybrid cross?
A cross that studies two traits
What is complete dominance?
The heterozygote and homozygous dominant individual are indistinguishable in phenotype (Yy = YY)
What is incomplete dominance?
The heterozygote has an intermediate phenotype (e.g., red + white = pink)
What is codominance?
Both alleles affect the phenotype in different but equal ways (AB blood type)
What are multiple alleles?
When a gene has more than two allelic forms (blood types: IA, IB, i)
What is polygenic inheritance?
A single trait is affected by multiple genes (height, skin color)
What is phenotypic plasticity?
The environment influences phenotype (sun exposure affecting skin tone)
What is a pedigree?
A diagram showing inheritance patterns across generations
How are males and females represented in pedigrees?
Males: squares, Females: circles
What does a shaded shape in a pedigree indicate?
The individual expresses the trait
What is a recessively inherited disorder?
A disorder that requires two copies of a defective gene (aa)
What are three examples of recessively inherited disorders?
Cystic fibrosis, Tay-Sachs disease, Sickle-cell disease
What is a dominantly inherited disorder?
A disorder that requires only one copy of a defective gene (A_)
What are two examples of dominantly inherited disorders?
Achondroplasia (dwarfism), Huntington’s disease
What is amniocentesis?
A procedure that removes amniotic fluid to test for genetic disorders
What is chorionic villus sampling (CVS)?
A procedure that removes placental cells for karyotyping
How can fetal DNA be analyzed noninvasively?
By isolating fetal DNA from the mother’s blood
