Biology LG 2 U4

What is protein synthesis?

The process where genes in the genome are used to make proteins, which determine cell structure and function.

What is a genome?

The complete set of DNA in an organism.

What are key features of the genome?

Found in most body cells, all cells have the same genome, and it contains all genetic instructions.

What is cell differentiation?

The process where cells become specialised.

How does cell differentiation occur?

Different genes are switched on/off, causing different proteins to be made, leading to specialised cells.

What is gene expression?

The process where a structural gene is read to produce a protein that determines phenotype.

What is a gene?

A section of DNA that codes for proteins.

What is a structural gene?

A section of DNA that codes for a specific protein.

How do genes determine traits?

By coding for proteins such as enzymes.

What is the genetic code?

The set of instructions in DNA used to build proteins.

How does the genetic code link genotype and phenotype?

DNA instructions are translated into proteins that determine traits.

What is non-coding DNA?

DNA that does not code for proteins but helps regulate gene expression and chromosome structure.

What is a regulatory gene?

Non-coding DNA that controls other genes by producing transcription factors.

What role does DNA play in protein synthesis?

DNA stores nucleotide triplets that determine amino acid order in proteins.

What are DNA triplets?

Groups of three nucleotides that code for one amino acid.

Why is amino acid sequence important?

It determines the protein’s structure and function.

What is transcription?

The process where DNA is copied into mRNA in the nucleus.

What is mRNA?

Messenger RNA that carries copied DNA instructions to the ribosome.

What is RNA polymerase?

An enzyme that builds mRNA using a DNA template.

What is a codon?

A group of three nucleotides on mRNA coding for one amino acid.

What is post-transcriptional modification?

Editing of pre-mRNA to form mature mRNA.

What is a split gene?

A gene containing exons interrupted by introns.

What is an intron?

A non-coding section removed during RNA processing.

What is an exon?

A coding section retained in mature mRNA.

What is splicing?

Removal of introns and joining of exons.

What is trimming in mRNA processing?

Removal of extra non-coding nucleotides.

What is capping?

Addition of a modified guanine to the start of mRNA.

What is tailing (poly-A tail)?

Addition of adenine nucleotides to the end of mRNA.

What is tRNA?

RNA molecules that carry specific amino acids to ribosomes.

Describe tRNA structure.

Cloverleaf-shaped with an amino acid attachment site.

What is an anticodon?

A triplet on tRNA complementary to an mRNA codon.

Explain the flow of genetic information in protein synthesis.

DNA triplet → mRNA codon → tRNA anticodon → amino acid → protein.

What is translation?

The process where ribosomes build polypeptides from mRNA instructions.

What is rRNA?

Ribosomal RNA that forms part of ribosomes.

What is the start codon?

AUG, which starts translation and codes for methionine.

What is a ribosome?

A structure where proteins are assembled.

What is a peptide bond?

A bond linking amino acids together.

What are stop codons?

UAG, UAA, and UGA, which end translation.

What is a polysome?

Multiple ribosomes translating one mRNA strand simultaneously.

What is gene regulation?

Control of when, where, and how much genes are expressed.

Why is gene regulation important?

It allows different cell functions and differentiation.

What are the three levels of gene regulation?

Pre-transcriptional, post-transcriptional, and translational.

What is pre-transcriptional control?

Regulation before transcription begins.

What is a transcription factor?

A protein that activates or blocks RNA polymerase.

What is post-transcriptional control?

Regulation after mRNA is made.

What is translational control?

Regulation during protein synthesis.

What is epigenetic control of gene expression?

Regulation through chemical changes to DNA or histones without changing DNA sequence.

What is the epigenome?

A system of gene control above the genome.

What is histone modification?

Chemical tagging of histones that changes chromatin packing.

What are histone proteins?

Positively charged proteins DNA wraps around.

What is a nucleosome?

DNA wrapped around histone proteins.

What is chromatin?

The DNA-protein complex making up chromosomes.

What is euchromatin?

Loosely packed chromatin with active genes.

What is heterochromatin?

Tightly packed chromatin with inactive genes.

What is DNA methylation?

Addition of methyl groups that can switch genes off.

What is a methyl group?

A small chemical tag (–CH₃) added to DNA.

What is an epigenetic marker?

A chemical tag affecting gene expression without altering DNA sequence.

What are totipotent stem cells?

Early embryonic cells capable of forming any cell type.

What are HOX genes?

Master control genes regulating body plans during development.

What are homeotic genes?

Genes controlling body structure positioning along the head-tail axis.

What is a homeobox?

A conserved DNA sequence enabling gene regulation.

What do HOX genes specifically control?

Body segmentation and positioning of structures.

What do HOX proteins do?

They determine the identity of body segments.

Do HOX genes create body segments?

No, they determine segment identity after segments form.

Why are HOX genes called master regulators?

They control many other genes and major developmental processes.

What can HOX gene mutations cause?

Major structural abnormalities such as legs growing instead of antennae.

Why are HOX genes evolutionarily important?

They are highly conserved across many species.

Give examples of segmentation in humans.

Vertebrae, spinal nerves, and abdominal muscles.

What is a HOX protein?

A transcription factor determining segment identity.

What is the relationship between HOX genes and transcription factors?

HOX genes produce transcription factors that regulate other genes.