4.1 DNA, Genes And Chromosomes Flashcards
Compare and contrast DNA in eukaryotic cells with DNA im prokaryotic cells
Similarities:
- Nucleotide structure is identical - deoxyribose attached to phosphate and a base
- Adjacent nucleotides joined by phosphodiester bonds, complementary bases joined by hydrogen bonds
- DNA in mitochondria / chloroplasts have similar structure to DNA in prokaryotes
- short, circular, no associated with proteins
Compare and contrast DNA in eukaryotic cells with DNA in prokaryotic cells
Differences:
- Eukaryotic DNA is longer
- Eukaryotic DNA is linear, prokaryotic DNA is circular
- Eukaryotic DNA is associated with histone proteins, prokaryotic DNA is not
- Eukaryotic DNA contain introns, prokaryotic DNA does not
What is a chromosome?
- Long, linear DNA + its associated histone proteins
- In the nucleus of eukaryotic cells with
What is a gene?
A sequence of DNA (nucleotides) bases that codes for:
- The amino acid sequence of a polypeptide
- Or a functional RNA (e.g. ribosomal RNA or tRNA)
What is a locus?
Fixed position a gene occupies on a particular DNA molecule
Describe the nature of the genetic code?
Triplet code : a sequence of 3 DNA bases, called a triplet, codes for a specific amino acid
Universal : The same base triplets code for the same amino acids in all organisms
Non-overlapping : Each base is part of only one triplet so each triplet is read as a discrete unit
Degenerate : an amino acid can be coded for by more than one base triplet
What are ‘non-coding base sequences’ and where are they found?
Non-coding base sequence - DNA that does not code for amino acid sequences / polypeptides
1. Between genes - e.g. non-coding multiple repeats
2. Within genes - introns
What are introns and exons?
Exon - Base sequence of a gene coding for amino acid sequences (in a polypeptide)
Intron - Base sequence of a gene that doesn’t code for amino acids, in eukaryotic cells with
