Biology Unit 1

Lipids

Organic compounds serving various cellular functions.

Selective permeability

Membranes allow specific molecules to pass.

Frameshift mutation

Mutation altering reading frame of mRNA.

Phenotype effect of frameshift mutation

Causes dysfunctional proteins, affecting organism's traits.

Transcription

Process of synthesizing mRNA from DNA.

Codons

Three-nucleotide sequences coding for amino acids.

Phospholipid bilayer

Regulates movement in and out of cells.

Formation of phospholipid bilayers

Driven by hydrophobic tails and hydrophilic heads.

Unsaturated bonds in lipids

Increase fluidity and flexibility of membranes.

5' cap in mRNA

Protects mRNA and aids ribosome recognition.

Poly(A) tail in mRNA

Stabilizes mRNA and regulates translation efficiency.

Spliceosome

Catalyzes intron excision and exon ligation.

5' UTR

Controls initiation of translation.

3' UTR

Influences efficiency of translation.

Nonsense mutation

Most deleterious mutation causing premature stop codon.

Silent mutation

Mutation with no phenotypic effect.

Translocation mutation

Chromosomal mutation involving segment transfer.

Transcriptional control

Gene expression control requiring least energy.

Positive control of transcription

Activator protein enhances transcription activity.

Redundant genetic code

Change in last nucleotide often does not alter amino acid.

Amino acid translation

First amino acid from mRNA is methionine (MET).

Energy storage in lipids

Lipids store energy for cellular processes.

Corepressor

Binds to activator to inhibit gene expression.

RNA Polymerase

Degrades mRNA before translation occurs.

Activator Protein

Binds to DNA to enhance transcription.

Prokaryotic Transcription

Occurs simultaneously with translation in cytoplasm.

Eukaryotic Transcription

Occurs in nucleus; translation occurs in cytoplasm.

Template Strand

Complementary to mRNA; used for transcription.

Coding Strand

Identical to mRNA sequence; not used for transcription.

Central Dogma

Describes flow of genetic information in cells.

mRNA Processing

Occurs in nucleus after transcription in eukaryotes.

Nontemplate DNA Strand

Has most similar nucleotide pairs to mRNA.

tRNA Movement in Ribosome

Moves through A, P, and E sites.

Cholesterol in Membranes

Moderates membrane fluidity and flexibility.

Genotype

Genetic makeup of an organism.

Phenotype

Observable characteristics resulting from genotype.

Point Mutation

Single nucleotide change in DNA sequence.

Missense Mutation

Single nucleotide change alters amino acid.

Nonsense Mutation

Change creates premature stop codon.

Deletion Mutation

Loss of one or more nucleotides.

Phospholipid Bilayer

Composed of hydrophilic heads and hydrophobic tails.

Alternative Splicing

Process that conserves energy by varying mRNA.

Chromatin Remodeling

Alters DNA accessibility for transcription.

Translation Rate

Speed of protein synthesis from mRNA.

Membrane Permeability

Increased by unsaturated lipids; decreased by cholesterol.

Inversion mutation

Nucleotide sequence reversed, e.g., ab to ba.

Translocation mutation

Segments of DNA exchanged between non-homologous chromosomes.

Duplication mutation

Nucleotide sequence repeated, e.g., ab to abab.

Template strand

DNA strand used to synthesize mRNA.

Coding strand

DNA strand with same sequence as mRNA.

Transcription initiation

RNA polymerase binds to promoter to start transcription.

Transcription elongation

RNA polymerase adds nucleotides to mRNA strand.

Transcription termination

RNA polymerase reaches terminator, releasing mRNA.

Promoter sequence

Marks the beginning of transcription in bacteria.

Terminator sequence

Signals the end of transcription in bacteria.

Sigma proteins

Guide RNA polymerase to promoter for transcription initiation.

Translation initiation

Ribosome assembles on mRNA at start codon.

Translation elongation

Ribosome moves along mRNA, adding amino acids.

Translation termination

Ribosome reaches stop codon, releasing polypeptide.

Start codon

AUG signals the beginning of translation.

Stop codon

UAA signals the end of translation.

Codon

Three-nucleotide sequence in mRNA coding for amino acid.

Anticodon

Three-nucleotide sequence in tRNA complementary to mRNA codon.

tRNA structure

Cloverleaf shape with anticodon and amino acid attachment.

Differential gene expression

Cells express different sets of genes.

Repressors

Inhibit transcription by blocking RNA polymerase.

Activators

Enhance transcription by aiding RNA polymerase binding.

Operons

Regulate multiple genes together in prokaryotes.

Gene expression regulation complexity

Allows eukaryotes for specialization and adaptation.

Transcriptional regulation

Prokaryotes use operons; eukaryotes use transcription factors.

Post-transcriptional regulation

Eukaryotic mRNA undergoes splicing and capping.

Translational regulation

Control of translation in both prokaryotes and eukaryotes.

Post-translational regulation

Modifies protein activity through phosphorylation or degradation.