Study Guide Genetics Exam 1
AGRY 320 Exam Preparation
Part 1: Classical Genetics
Understand genotypes and phenotypes: infer from given alleles.
Genotype: Genetic makeup of an organism 'Pp' (heterozygous for purple flower color).
Phenotype: Observable physical or biochemical characteristics of an organism, determined by both genetic makeup (genotype) and environmental influences: Purple flowers, since purple is the dominant trait.
Define homozygous vs. heterozygous genotypes.
Homozygous—> Same allele “Aa”
Heterozygous—> Different allele “Ab”
Generate genotypic and phenotypic ratios for monohybrid and dihybrid crosses.
Genotypic Ratio: Ratio of genotypes in a cross, for a monohybrid cross typically 1:2:1.
Phenotypic Ratio: Ratio of phenotypes in a cross, for a monohybrid cross generally 3:1.
In dihybrid crosses, the phenotypic ratio is usually 9:3:3:1, while genotypic ratios can be more complex.
Know stages of the cell cycle, mitosis and meiosis; derive DNA molecules, chromosomes, and tetrads during each step.
Cell Cycle: The series of phases that a cell goes through as it grows and divides. The main stages include Interphase (which consists of G1, S, and G2 phases) and the Mitotic phase (which includes mitosis and cytokinesis).
Mitosis: The process of cell division that results in two genetically identical daughter cells, taking place in several stages: prophase, metaphase, anaphase, and telophase.
Meiosis: A special type of cell division that reduces the chromosome number by half and results in four genetically distinct gametes. It includes two rounds of division: meiosis I and meiosis II.
During these processes, DNA molecules coil into chromosomes, and during meiosis, homologous chromosomes pair up to form tetrads in prophase I.
Identify chromosomes, sister vs. non-sister chromatids, and homologous chromosomes using diagrams.
Recognize types of epistasis and derive phenotype ratios.
Dominant epistasis: When a dominant allele at one locus masks the expression of alleles at another locus, leading to specific phenotype ratios such as 12:3:1.
Recessive epistasis: Occurs when two recessive alleles at one locus inhibit the expression of alleles at another locus, often resulting in a 9:3:4 phenotype ratio.
Duplicate epistasis: In a plant, two genes (A and B) control flower color.
If the plant has at least one dominant A or one dominant B, the flowers are purple. Only when the plant is aabb (both genes recessive) are the flowers white.
Understand sex-linked traits and their associated genotypic and phenotypic ratios.
Part 2: Molecular Genetics and Molecular Biology
Draw and describe the biochemical structure of DNA (building blocks and bonding).
Know models proposed for DNA replication, including the semiconservative model that suggests each strand of the parental DNA serves as a template for the new complementary strand.
1.Conservative Model: The original DNA molecule serves as a template, but both strands remain intact and a completely new double helix is formed.
2.Dispersive Model: Parental DNA strands are broken into fragments, and new DNA is synthesized in such a way that both original and new compose parts of both strands.
Explain key experiments and scientists leading to DNA's identification as the inheritance molecule.
Understand DNA packing from double-helix to chromosome structure.
Describe models of DNA replication and the experiment revealing the correct model.
Show knowledge of DNA replication process, including building blocks, enzymes, and proteins; demonstrate with diagrams.
Explain the central dogma: DNA to RNA to protein to traits through diagrams and written descriptions.
Understand the eukaryotic gene model; label and describe its features.
Infer RNA sequences from the genetic code; describe RNA processing (5’ cap, splicing, poly A tailing).
Describe transcription process with all components involved.
Understand the genetic code and use a codon table to infer amino acid sequences from gene sequences.
Define mutation types; determine amino acid changes from DNA-level mutations (missense, nonsense, frameshift).