3.4.1 - DNA, genes and chromosomes Flashcards
how is DNA stored in eukaryotic cells?
-contains long, linear DNA molecules which are wound around proteins called histones
-a DNA molecule and its associated histone proteins form a chromosome which are found in the nucleus
what is the role of histone proteins in eukaryotic DNA?
-help support the proteins
-after the DNA is wound around them, the proteins coil up to make them a compact chromosome
what is the DNA in mitochondria and chloroplasts like?
-it is not associated with histone proteins
-its circular and shorter than DNA in the nucleus
how is prokaryotic DNA stored?
-molecules are shorter and circular
-DNA is not wound around histones, it condenses to fit in the cell by supercoiling
what is a gene and its function?
-a sequence of DNA bases that codes for either:
*the amino acid sequence of a polypeptide
*a functional RNA molecule (rRNA, tRNA)
what is functional RNA?
-RNA molecules, other than mRNA which perform special tasks during protein synthesis such as tRNA and rRNA
what is a locus?
the fixed position a gene occupies on a particular DNA molecule
what are introns in DNA?
sections of genes that do not code for a polypeptide.
they separate exons from each other
what are exons in DNA?
parts of the gene that do code for amino acids
what does ‘read in triplets’ mean in terms of the genetic code?
3 bases code for a single amino acid
what does non-overlapping mean in terms of the genetic code?
each base is only part of one codon
what does universal mean in terms of the genetic code?
the same codon codes for the same amino acid in all organisms
what does degenerate mean in terms of the genetic code?
an amino acid can be coded for by more than one codon
