DNA, genes and chromosomes Flashcards
What is the fixed position occupied by a gene on a DNA molecule?
Locus.
Describe how a gene is a code for the production of a polypeptide (not including transcription or translation).
The sequence of DNA bases determines the sequence of amino acids in a polypeptide.
Define the term exon.
An exon is a coding region used to build polypeptides.
What is the amino acid sequence for DNA template AGG CGT CCT GGA?
The mRNA codons are UCC GCA GGA CCU → Amino acids: Serine, Alanine, Glycine, Proline.
How is a phosphodiester bond formed between two nucleotides in DNA?
By a condensation reaction between the phosphate of one nucleotide and the sugar of another.
Name the protein associated with DNA in a chromosome.
Histone.
Give three differences between DNA in the nucleus of a plant cell and in a prokaryotic cell.
- Eukaryotic DNA is linear, prokaryotic is circular.
- Eukaryotic DNA is associated with histones, prokaryotic DNA is not.
- Eukaryotic DNA contains introns, prokaryotic DNA usually does not.
Define ‘non-coding base sequences’ and describe where non-coding multiple repeats are positioned in the genome.
Non-coding sequences do not code for polypeptides. Repeats are found between genes.
Give three ways DNA in a chloroplast differs from nuclear DNA.
- Chloroplast DNA is circular.
- It is not associated with histones.
- It does not contain introns.
Give one structural difference between a DNA nucleotide and an RNA nucleotide.
DNA contains deoxyribose; RNA contains ribose.
Give two reasons why some mutations do not change the structure of a polypeptide.
- The mutation may occur in an intron.
- The code is degenerate, so the same amino acid may be coded.
Compare DNA in eukaryotic cells with DNA in prokaryotic cells.
Eukaryotic DNA is linear, has histones, and contains introns; prokaryotic DNA is circular, lacks histones, and rarely contains introns.
Suggest one reason why stain binds more in some areas of chromosomes.
Some regions have more tightly coiled DNA or more proteins.
What is a homologous pair of chromosomes?
A pair of chromosomes with the same genes in the same loci, one from each parent, but possibly different alleles.
