B14 - Flashcards for Nucleic Acids Unit

What is the main function of nucleic acids in the body?

Nucleic acids carry genetic information;

of organisms in the sequence of their nucleotide bases, usually in DNA;

which determines inherited traits and guides protein synthesis;

through production of mRNA;

How does the structure of nucleic acids allow hereditary information to be stored?

The linear sequence of four complementary bases encodes information;

Base-pairing allows accurate copying and transmission;

e.g. A pairs with T and C pairs with G;

The sugar-phosphate backbone provides stability;

What are chromosomes made of and what do they contain?

Chromosomes consist of tightly packed DNA and associated proteins;

They contain genes which are units of hereditary information;

Define a gene?

A gene is a defined length of DNA;

that codes for a specific protein or functional RNA molecule;

What were the main goals of the Human Genome Project?

To sequence the entire human genome;

To identify all human genes;

To annotate genetic functions;

To enable personalised medicine and advance understanding of genetic diseases

What outcomes arose from sequencing the human genome?

A complete DNA sequence for humans, the genome;

Identification of disease-associated variations of genes;

New targets for drug development;

How does the sequence of bases in a gene determine protein composition?

Each triplet of bases (codon) on mRNA specifies one amino acid;

The order of codons determines the amino acid sequence;

This amino acid order determines final protein shape and function;

Why do different amino acid sequences produce different protein shapes?

A different order of amino acids leads to a different structure

because the protein will fold differently

What is a mutation and how does it generate new alleles?

A mutation is a random change in the DNA base sequence;

Mutations in genes create allele variants;

New alleles contribute to genetic diversity (variation) and evolution;

What causes mutations in DNA?

Random errors in copying DNA;

ionising radiation;

mutagens (carcinogens);

What effect does the sickle cell mutation have on haemoglobin?

A single base substitution in the (β-) hemoglobin gene replaces one amino acid with another;

Abnormal haemoglobin forms as it sticks together in rod shapes;

Red blood cells become sickle-shaped causing anaemia and blockages in blood vessels;

How does DNA control cell function by controlling protein production?

DNA stores instructions for proteins including enzymes, structural proteins and receptors;

therefore changes in genes control changes in proteins and therefore cellular function;

Describe the process of transcription in protein synthesis?

DNA double helix is unwound at the gene;

(RNA polymerase) an enzyme synthesises new complementary mRNA using base-pairing rules;

mRNA detaches and exits the nucleus to the cytoplasm;

Where does mRNA go after being made?

mRNA passes from the nucleus into the cytoplasm;

What roles do ribosomes play in translation?

Ribosomes read the mRNA codons;

They catalyse a peptide bond formation between amino acids delivered by tRNA;

each codon on mRNA gives a specific amino acid;

How are amino acids assembled into a polypeptide?

(tRNA molecules bring) specific amino acids;

are linked by the ribosome into a long chain called a polypeptide;

What determines the specific sequence of amino acids in a protein?

The order of codons on the mRNA, which is transcribed from the DNA base sequence of the gene

Why do most body cells contain identical genes but express different proteins?

All body (somatic) cells contain the full genome;

Cell differentiation arises from selective gene expression;

Only genes needed for a cell's function are transcribed

What is the central dogma of molecular biology?

Information flows from DNA to RNA to protein; Transcription produces mRNA;

Translation uses mRNA to synthesise proteins

How do DNA mutations drive evolution?

Mutations introduce genetic variation;

Natural selection acts on differences;

Beneficial alleles increase in frequency over generations

Where does transcription take place?

Transcription takes place in the nucleus

Where does translation occur?

Translation occurs in the cytoplasm at ribosomes

Which cellular structures carry out protein synthesis?

Ribosomes

Compare the bases present in DNA and RNA?

DNA contains adenine, thymine, cytosine and guanine; RNA contains adenine, uracil, cytosine and guanine

Compare the sugar component of DNA and RNA?

DNA contains deoxyribose sugar;

RNA contains ribose sugar;

Compare the number of strands in DNA and RNA?

DNA is typically double-stranded forming a stable double helix;

RNA is typically single-stranded;

Compare the cellular location of DNA and RNA?

DNA is located mainly in the nucleus (and in mitochondria and chloroplasts in eukaryotes);

RNA is synthesised in the nucleus and functions primarily in the cytoplasm