Chapter 11: The Instructions for Life - DNA and RNA

Vocabulary flashcards covering the key concepts and terms from the lecture notes.

Hershey and Chase Experiment Conclusion

DNA, not protein, carries the genetic material responsible for heredity.

DNA's functions

To explain diversity of life, copy itself, store information and control cell activities and change over time allowing evolution

Components of a DNA Nucleotide

A sugar (deoxyribose), a phosphate group, and a nitrogenous base (A, T, C, or G).

Discoverers of the Double Helix Structure

James Watson and Francis Crick.

Chargaff's Rule

A=T and G=C.

Erwin Chargaff's contribution

Showed that A=T and G=C.

Rosalind Franklin's contribution

Produced X-ray diffraction images of DNA that revealed its helical shape.

Variability in DNA is due to

The order of base pairs.

Key feature of Franklin's Photo 52

A clear X-shaped diffraction pattern indicating a helix.

Sides of the DNA ladder

Sugar-phosphate backbone.

Rungs of the DNA ladder

Paired nitrogenous bases (A-T and G-C).

Complementary base pairing

Ensures consistent rung width.

Direction of DNA strands

5' to 3' and 3' to 5'.

Purpose of DNA Replication

Cells must copy their DNA before cell division for growth and tissue repair.

When does DNA replication occur?

S phase of the cell cycle.

Semi-conservative replication

One original (parent) strand is conserved in each new double helix.

Helicase

Breaks hydrogen bonds between bases and unwinds the double helix.

DNA Polymerase

Adds new nucleotides to the growing daughter strand.

DNA Ligase

Seals any breaks in the sugar-phosphate backbone to complete the daughter strand.

Replication in eukaryotic cells

DNA replication starts at multiple origins of replication along the chromosome.

Synthesized continuously towards the replication fork

Leading strand.

Made discontinuously in short pieces called Okazaki fragments

Lagging strand.

RNA

Ribonucleic acid.

Main role of RNA

Assists DNA in protein synthesis.

Three types of RNA

mRNA, tRNA, rRNA.

mRNA function

Carries genetic information from DNA to the ribosomes.

tRNA function

Transfers amino acids from the cytoplasm to the ribosomes.

rRNA function

Joins with proteins to form ribosome subunits.

The Central Dogma

DNA -> RNA -> Protein.

Gene Expression

The use of information from a gene to make a functional protein.

Two Key Processes of Gene Expression

Transcription and Translation.

Codon

A group of three bases in mRNA that codes for one amino acid.

Stop Codons

Signaling the end of a protein.

AUG Codon

Codes for methionine (Met) and is the start codon for translation.

Transcription

A strand of RNA is synthesized that is complementary to a portion of DNA.

Transcription Initiation

RNA polymerase binds to the promoter region of DNA.

mRNA Processing

Adding a cap and a poly-A tail and splicing.

Introns

Non-coding regions that are removed during mRNA processing.

Exons

Coding regions that are joined together to form a continuous sequence.

Alternative Splicing

Allows the production of different protein products from a single gene.

tRNA full name

Transfer RNA.

tRNA Structure

A single-stranded nucleic acid that folds into a cloverleaf shape.

Ribosome binding sites

P site, A site, E site.

Initiation

The ribosome assembles around the mRNA and the first tRNA binds to the start codon.

Elongation

The ribosome moves along the mRNA, adding amino acids one by one.

Termination

The ribosome reaches a stop codon, releasing the completed polypeptide.

Cell Specialization

Different cell types contain a unique mix of proteins.

Housekeeping Genes

Active in all cells and govern common functions.

Operon

A cluster of genes plus control sequences regulating transcription.

Promoter

DNA sequence where RNA polymerase binds.

Operator

DNA sequence where a repressor binds to control gene access.

Chromatin condensation, DNA transcription and mRNA processing within the nucleus. mRNA translation and protein activity within the cytoplasm.

Where regulation effect happens in eukaryotic cells

Chromatin Condensation

Tightly compacted chromatin genes turned off

Heterochromatin

Darkly staining, tightly packed inactive chromatin.

Epigenetics

Inheritance of changes in gene expression without altering the DNA sequence.

Transcription Factors

DNA-binding proteins that help RNA polymerase attach to the promoter.

Transcription Activators

Special DNA-binding proteins that speed up transcription.

Cytoplasmic proteins Control

Whether mRNA translation occurs.

Ras protein

Functions in signal transduction pathways and continuous activation leads to cancer by causing uncontrolled cell division