Ch 13.2, 13.3, 14.1, 14.2, 14.4 Genetics (DNA and RNA)

Learning Objectives Review: DNA, RNA, and Genetics

1. Role of DNA in Heredity (3 functions)

• Storage of Genetic Information: DNA contains the instructions for building and maintaining an organism.

• Replication: DNA can make exact copies of itself to pass genetic information to new cells.

• Gene Expression: DNA sequences are used to make RNA and proteins, which determine traits.

2. Chemical Components of DNA

• Nucleotides: Building blocks made of:

  • Sugar: Deoxyribose

  • Phosphate group

  • Nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C)

• Bases pair specifically: A with T (2 hydrogen bonds), G with C (3 hydrogen bonds).

3. Role of DNA Polymerase in Copying DNA

• Enzyme that adds complementary nucleotides to the original DNA strand during replication.

• Proofreads and corrects errors to ensure accurate copying.

4. How DNA Differs from RNA

5. How the Cell Makes RNA (Transcription)

• RNA polymerase binds to the promoter on DNA.

• It unwinds DNA and assembles RNA nucleotides complementary to the DNA template.

• RNA strand is processed (introns removed, exons spliced) before leaving the nucleus.

6. How the Genetic Code Works

• Genetic code is read in codons (sets of 3 bases).

• Each codon specifies an amino acid or a stop signal during protein synthesis.

• Code is universal and redundant (multiple codons can code for the same amino acid).

7. Role of the Ribosome in Protein Assembly

• Ribosomes read mRNA codons.

• tRNA molecules bring specific amino acids matching the codon’s anticodon.

• Ribosome links amino acids into a polypeptide chain (protein).

8. How Mutations Change Genetic Information

• Mutations are changes in DNA sequence.

• Types:

  • Point mutation: Change in a single base.

  • Frameshift mutation: Insertions or deletions that shift the reading frame.

• Mutations can be caused by errors during replication or environmental factors (mutagens).

9. How Mutations Affect Genes

• Can alter protein structure/function.

• May have no effect (silent mutation), harmful effects, or occasionally beneficial traits.

• Can lead to genetic diseases or increased variation in populations.

10. Cause and Effect: DNA, Chromosomes, and Traits

• DNA is tightly packed into chromosomes.

• Chromosomes carry genes, the instructions for traits.

• Offspring inherit chromosomes from parents, passing traits via DNA sequences.

11. Cause and Effect: DNA, Proteins, and Traits

• Genes (DNA) code for proteins.

• Proteins perform functions or form structures that result in observable traits.

• Changes in DNA affect proteins, which can alter traits.

12. Regulation of DNA Expression (Introns, Exons, etc.)

• Genes contain exons (coding regions) and introns (non-coding).

• Introns are removed in RNA processing.

• Regulation of which exons are included affects which proteins are made (alternative splicing).

13. Genetic Variation from Meiosis Errors or Mutations

• Meiosis errors: Nondisjunction can cause abnormal chromosome numbers (e.g., polyploidy).

• Mutations from environmental mutagens can introduce new genetic variations.

• These variations contribute to diversity and evolution.

Key Terms Summary

• Base pairing: A-T (DNA), A-U (RNA), G-C

• Complementary: Bases pair in a specific way

• Nitrogenous bases: A, T, G, C, U (RNA)

• Nucleic acid: DNA and RNA molecules

• Nucleotide: Sugar + phosphate + base

• Double helix: DNA structure of two strands twisted

• Antiparallel strands: DNA strands run in opposite directions

• Replication: DNA copying process

• DNA polymerase: Enzyme for replication

• Hydrogen bonds: Bonds between bases

• Covalent bonds: Bonds in sugar-phosphate backbone

• Sugar-phosphate backbone: Structural framework of DNA/RNA

• Helicase: Enzyme that unwinds DNA

• RNA: Ribonucleic acid, involved in protein synthesis

• mRNA: Messenger RNA carrying code from DNA

• rRNA: Ribosomal RNA, part of ribosome

• tRNA: Transfer RNA, carries amino acids

• Transcription: Making RNA from DNA

• RNA polymerase: Enzyme that synthesizes RNA

• Promoter: DNA region where RNA polymerase binds

• Intron: Non-coding RNA section removed during processing

• Exon: Coding RNA section kept in mature mRNA

• Mutations: Changes in DNA sequence

• Point mutation: Single base change

• Frameshift mutation: Insertion/deletion changing reading frame

• Mutagen: Agent causing mutations

• Polyploidy: Having extra sets of chromosomes

• Translation: Making protein from mRNA

• Codon: Three-base sequence in mRNA coding for amino acid

• Anticodon: tRNA sequence complementary to codon

• Amino acid: Building block of proteins

• Genes and proteins: Genes code for proteins

• Polypeptide → protein: Chain of amino acids folds into functional protein

• Central dogma of biology: DNA → RNA → Protein

Review Tip: Compare Replication, Transcription, and Translation