Prepare for AP Biology Genetics questions with this review and practice answers. This covers Mendelian genetics, DNA replication, gene expression, and heredity.
Q: Dominant
Answer: If present, always expressed
Q: Recessive
Answer: Carried but “hidden” (not expressive)
Q: Gene Pairs
Answer: Alleles
Q: Why do genes occur in pairs?
Answer: One comes from each parent on the homologous pair.
Q: Homozygous
Answer: Both alleles are identical (2 dominant/2 recessive)
Q: Heterozygous
Answer: Both alleles are different (1 dominant & 1 recessive)
Q: Genotype
Answer: Homozygous Dominant (AA)Heterozygous (Aa)Homozygous Recessive (aa)
Q: Phenotype
Answer: Expression of GenesDominant: Most common form of appearanceRecessive: Less common form of appearance
Q: P1 Generation
Answer: Parents of the 1st Generation
Q: Law of Segregation
Answer: Homologous Pairs separate in Meiosis
Q: Purebred Cross
Answer: Cross between 2 parents homozygous for the traitF1 Genotype: 0:4:0F1 Phenotype: 4:0
Q: Monohybrid Cross
Answer: Cross between 2 parents heterozygous for the traitGenotype: 1:2:1Phenotype: 3:1
Q: Test Cross
Answer: Cross done to determine the genotype of an individual who shows the dominant phenotype (cross w/ recessive)Genotype: (Homozygous) 0:4:0, (Heterozygous) 0:2:2Phenotype: (Homozygous) 4:0, (Heterozygous) 2:2
Q: If recessive shows in offspring?
Answer: Parent who showed dominant must have carried recessive
Q: Dihybrid Cross
Answer: Cross between 2 parents heterozygous for 2 traitsGenotype: 1:2:1:2:4:2:1:2:1Phenotype: 9:3:3:1
Q: Barr Body
Answer: Inactivated and highly condensed chromosome
Q: Non-disjunction
Answer: Failure of homolofues to separate properly during Meiosis
Q: Polygenes
Answer: More than one pair of genes code for a trait and all are carried; recognized by a range in phenotypes
Q: Incomplete Dominance
Answer: Neither gene dominates completely, heterozygote is the intermediate phenotype; type of monohybridGenotype: 1:2:1Phenotype: 1:2:1
Q: Co-Dominance
Answer: Both genes dominate, heterozygote shows both forms of the traits; type of monohybridGenotype: 1:2:1Phenotype: 1:2:1
Q: Multiple Alleles
Answer: More than one pair of genes for a trait but only one pair is carried
Q: Blood Type (description)
Answer: 3 genes, only get twoPolygenic b/c of Type AB
Q: Sex Linked Traits
Answer: Traits governed by genes on x-chromosome, recessive
Q: Linked Genes
Answer: Genes for traits carried on the same chromosome pair; can’t independently assort except for crossing over
Q: Chromosome disorders
Answer: Result from non-disjuntion, failure of homologous pairs to separate in meiosis, causes gamete and therefore zygote to have wrong chromosome number
Q: Trisomy
Answer: Gain an extra autosomeEx. Downs
Q: Monosomy
Answer: Lose a copy of an autosomeEx. Turners
Q: Difference b/t Genetic Disorder and Chromosomal Disorder
Answer: Genetic Disorder: Wrong nucleotide; affects one geneChromosome Disorder: Affects lots of genes; mssing a lot or have too much genetic information
Q: Epistasis
Answer: Interactaction between 2 nonallelic genes, where one interferes with the expression of another
Q: Pleiotropic Gene
Answer: One gene that affects more than one phenotypeGenotype Ratio: 2:1