B5 DNA Flashcards
what is DNA
a molecule that carries genetic information.
why is DNA important
• forms the entire genome of an organism
• important for all cellular functions
• found in the nucleus of almost all cells – chromatin strands and chromosomes
are made up of DNA and proteins
what is the structure of DNA
Each DNA molecule consists of two strands twisted around each other to form a double helix.
what is a nucleotide
the basic unit of DNA
what is each nucleotide made up of
- sugar molecule (deoxyribose)
- phosphate group
- nitrogenous base: adenine(A)/ cytosine(C)/ guanine(G)/ thymine(T)
how do we form polynucleotides
Nucleotides are joined to form long chains called polynucleotides.
what is a DNA molecule made up of
The DNA molecule is made up of two anti-parallel polynucleotide chains.
what are the complementary base pairs
Complementary base pairs:
adenine (A) and thymine (T)
cytosine (C) and guanine (G)
how are complementary base pairs joined
Complementary bases are joined by hydrogen bonds.
what is a gene
A gene is a sequence of DNA nucleotides (bases) that controls the formation of a single polypeptide, which can be used to make proteins.
what does each gene consist of
Each gene consists of two polynucleotide chains. The template chain is the one that determines the type of protein made.
how is an amino acid coded and how is this read
• Three bases (= a codon) code for one amino acid. The genetic code is ‘read’ as triplets.
what is transcription
Transcription: the process by which the DNA template is used to make a single-stranded messenger RNA (mRNA).
how does mRNA get formed and how does this leave the nucleus
o mRNA has a base sequence complementary to that of template DNA
o mRNA carries genetic code out of nucleus to the cytoplasm
what is translation
Translation: the process by which the sequence of mRNA codons is used to make a polypeptide
how does mRNA get turned into a protein
o the message in mRNA is translated into a sequence of amino acids
which are joined by peptide bonds to form a polypeptide, which will eventually fold to form a protein
what is a genetic mutation
a change in the DNA (nucleotide) sequence of a gene
what can a genetic mutation alter and how does this affect a trait
• A mutation may or may not lead to a change in the protein product.
• A change in the protein product may or may not lead to an observable
phenotype.
what are some phenotypic changes caused by genetic mutation
• Examples: albinism, sickle-cell anaemia
what is each gene made up of
Each gene is made up of a specific sequence of bases (or nucleotides), which forms the genetic code.
where does transcription occur
o occurs in the nucleus
where does translation occur
o occurs at the ribosomes (in cytoplasm)
