Genetic loci Flashcards
Every chromosome consists of a
long DNA molecule that codes for several different proteins
gene
is a sequence of nucleotide bases in a DNA molecule that codes for the production of a specific sequence of amino acids, that in turn make up a specific polypeptide (protein)
locus(loci) is
The position of a gene on a chromosome
Each gene can exist in two or more different forms called
alleles
Different alleles of a gene have slightly different……………………… but
Different alleles of a gene have slightly different nucleotide sequences but they still occupy the same position (locus) on the chromosome
The DNA nucleotide base code found within a gene is a
three-letter, or triplet, code
Each sequence of three bases (in other words each triplet of bases) codes for one amino acid
codons are what
These triplets of bases are known as codons (each codon codes for a different amino acid – there are 20 different amino acids that cells use to make up different proteins)
Why is DNa described as non overlapping
Overlapping refers to how the code is read. The first three bases are read as one codon, then the next three as the second etc, therefore each base is read only once and the bases do not overlap.
There are four bases so there are 64 different triplets possible (4to power of3), yet there are only … amino acids that commonly occur in biological proteins
20
Why can DNA be described as degenerate
This results in multiple codons coding for the same amino acids thus the code is said to be degenerate (this can limit the effect of mutations)
Why is DNA described as universal
meaning that almost every organism uses the same code (there are a few rare and minor exceptions)
This means that the same codons code for the same amino acids in all living things (meaning that genetic information is transferable between species)
