DNA & Gene Structure Quiz

DNA & Gene Structure

• Homozygous trait: Both alleles are the same (AA or aa).
• Heterozygous trait: Two different alleles (Aa).
• Mendel's Law of Segregation: Each individual has two alleles for a gene; alleles segregate during gamete formation, each gamete carries one allele.
• Mendel's Law of Independent Assortment: Alleles for different traits assort independently.
• Complete dominance: One allele completely masks the other.
• Codominance: Both alleles contribute equally and visibly.
• Incomplete dominance: The heterozygote has an intermediate phenotype.
• Example: Brown eyes (B) vs. blue eyes (b)--complete dominance; AB blood type—codominance; pink flowers (RW) from red (RR) and white (WW) flowers—incomplete dominance.
• Allele: A variant form of a gene.
• Dominant allele: Masks recessive allele in heterozygote.
• Polygenic inheritance: Traits controlled by multiple genes (e.g., skin color).
• Epistasis: One gene affects the expression of another (e.g., coat color in Labradors).
• Gene: Sequence of DNA coding for a protein or RNA molecule.
• Locus: Specific location of a gene on a chromosome.
• Linked genes: Genes close together on same chromosome; inherited together.
• Nondisjunction: Chromosome failure to separate during cell division.
• Aneuploidy: Abnormal chromosome number.
• Sex-linked traits: Traits associated with genes on sex chromosomes (e.g., SRY gene).
• Nucleotides of DNA: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
• Complementary base pairing: A with T (or U in RNA); C with G.
• DNA replication: Semiconservative process.
• Helicase: Unwinds DNA double helix.
• Topoisomerase: Relieves tension caused by unwinding.
• Single-strand binding proteins: Prevent re-annealing of DNA strands.
• RNA primer: Provides starting point for DNA polymerase.
• DNA polymerase: Adds nucleotides to growing strand (5' to 3').
• Lagging strand: Synthesized discontinuously (in Okazaki fragments).
• Leading strand: Synthesized continuously.

DNA Replication & Structure

• DNA organization: Replication bubble with two replication forks.
• DNA strand synthesis direction: 5' to 3'.
• Okazaki fragments: Short DNA segments on the lagging strand.
• DNA ligase: Connects Okazaki fragments.
• Replication fork: Y-shaped region of DNA where replication occurs.
• Origin of replication: Specific site where replication begins.
• Mutation: A change in DNA sequence.
• Telomeres: Protective structures at the ends of chromosomes.
• Transcription: Making an RNA copy of a gene (occurs in nucleus).
• Translation: Synthesizing a protein from mRNA (occurs in cytoplasm).
• RNA polymerase: Enzyme that carries out transcription.
• RNA vs. DNA: RNA uses uracil (U) instead of thymine (T).
• Codons: Three-nucleotide sequences in mRNA that code for amino acids.
• Anticodons: Complementary sequences in tRNA that pair with codons.
• Exons: Coding regions of genes; introns: non-coding regions.
• mRNA: Carries genetic information from DNA to ribosome.
• tRNA: Brings amino acids to ribosome.
• rRNA: Makes up ribosomes.
• Ribosomes: Sites of protein synthesis.
• Three ribosome binding sites: A, P, and E site.
• Types of mutations: Point mutations (substitution), insertions, deletions (frameshift).