DNA, genes and chromosomes Flashcards
What are the three components of nucleotides?
A pentose sugar, a phosphate group, an 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).
- It is double-stranded, and hydrogen bonds between the bases form a helix shape.
Describe the role of DNA.
Carries genetic information, determines our inherited characteristics.
Describe the structure of RNA.
- Made up of a ribose sugar, a phosphate group, and one of four organic bases (A,C,G,U).
- It is single stranded.
Describe the role of RNA.
Transfers genetic information from DNA to ribosomes for protein synthesis.
Which bases are purine and which are pyrimidine?
Purine (double ring) = adenine, guanine.
Pyrimidine (single ring) = cytosine, thymine, uracil.
How is DNA in eukaryotic cells different from in
prokaryotic cells?
Eukaryotic cells: - found in nucleus, long and linear. -Associated with histone proteins to form chromosomes. Prokaryotic cells: -short and circular. -Not associated with proteins.
What is the genetic code?
The order of bases on DNA. Consists of codons (triplets of bases that code for a particular amino acid).
Identify 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 of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide. Can also 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 and introns?
Exons= regions of DNA that code for amino acid sequences. Separated by
one or more introns.
Introns= regions of DNA that do not code for anything.
Where are introns found?
- between exons
- within genes
