AQA A Level Biology: DNA, Genes and Chromosomes Flashcards
What is a gene?
A section of DNA that codes for a polypeptide or functional RNA.
What is a genome?
The complete set of genes in an organism.
What is a proteome?
The full range of proteins a cell can produce.
How is DNA stored in prokaryotic cells?
As circular DNA, not associated with histones, and sometimes plasmids.
How is DNA stored in eukaryotic cells?
As linear DNA associated with histones, found in chromosomes within the nucleus.
What is a locus?
The specific position of a gene on a chromosome.
What is the genetic code?
The sequence of bases in DNA that determines the sequence of amino acids in a protein.
What are the three properties of the genetic code?
- Universal – The same codons code for the same amino acids in all organisms.
- Degenerate – More than one codon can code for the same amino acid.
- Non-overlapping – Each base is read only once in the triplet code.
What is a codon?
A sequence of three nucleotide bases on mRNA that codes for a specific amino acid.
What is a start codon?
A specific codon (AUG) that signals the start of translation.
What is a stop codon?
A codon that signals the end of translation (UAA, UAG, UGA).
What are the two types of nucleic acids?
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
What are the components of a nucleotide?
A phosphate group, a pentose sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base.
What are the four nitrogenous bases in DNA?
Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
How do the bases pair in DNA?
Adenine pairs with Thymine (A-T), and Cytosine pairs with Guanine (C-G).
What type of bond holds the DNA strands together?
Hydrogen bonds between complementary bases.
What is meant by ‘antiparallel’ in DNA structure?
The two strands of DNA run in opposite directions (5’ to 3’ and 3’ to 5’).
What is a homologous pair of chromosomes?
A pair of chromosomes (one from each parent) that carry the same genes but may have different alleles.
What is a diploid cell?
A cell containing two sets of chromosomes (2n).
What is a haploid cell?
A cell containing one set of chromosomes (n), such as gametes.
What is an allele?
A different version of a gene.
What is a mutation?
A change in the DNA sequence that may alter a protein’s function.
