DNA, genes and chromosomes Flashcards
(14 cards)
What are the 3 components of a nucleotide?
Pentose sugar
Phosphate group
Organic base
Describe the structure of DNA
Made up of a deoxyribose sugar, a phosphate group and one of four organic bases (A, C, G, T).
DNA is double stranded
Hydrogen bonds between bases form a helix shape
Describe the role of DNA
Carries genetic info
Determines inherited characteristics
Describe the structure of RNA
RNA is made up of a ribose sugar, a phosphate group and one of four organic bases (A, C, G, U)
RNA is single stranded
Describe the role of RNA
Transfers genetic info from DNA to RIBOSOMES for protein synthesis
Which bases are purine, which are pyramidine?
Purine (double ring) - A,G
Pyrimidine (single ring) - C,T and U
How is DNA in eukaryotic cells different from DNA in prokaryotic cells?
Eukaryotic cells -DNA found in nucleus, long and linear
Associated with histone proteins to form chromosomes
(Mitochondria and chloroplasts contain prokaryotic-like DNA)
Prokaryotic cells - short and circular
Not associated with proteins
What is the genetic code?
Order of bases on DNA
Consists of codons (triplets of bases that code for a particular amino acid)
Identify the features of the genetic code
Non overlapping - each triplet is only read once
Degenerate - more than one triplet codes for the same amino acid (64 possible triplets for 20 amino acids)
Universal - same bases and sequences used by all species
What is a gene?
A sequence on a DNA molecule that codes for:
a specific sequence of amino acids to make a polypeptide
code for functional RNA
What is a locus?
The fixed position on a DNA molecule occupied by a gene
What is an allele?
Different versions of the same gene, found at the same locus on a chromosome
What are exons?
Regions of DNA that code for amino acid sequences. Separated by one or more introns
What are introns?
Regions of DNA that do not code for anything
