DNA., genes and chromosome Flashcards
define gene
a section of DNA that codes for making a polypeptide and functional RNA
define locus
location of a particular gene on a chromosome
How do genes determine nature and development of organisms?
- Gene contains code for the amino acid sequence of a polypeptide
- Determine proteins in an organisms
- enzymes are proteins that control chemical reaction so they’re responsible for an organisms development and activities
define allele
alternative form of gene
define chromosome
DNA double helix molecule
tightly coiled up DNA composed of 2 identical chromatids held together at the centromere.
the DNA in chromosomes is held by histone proteins.
homologous chromosome
pairs of matching chromosomes (one from each parent)
-the homologous pairs are the same size and carry the same genes but might have different alleles of those genes.
what are human sex cells called
haploid cells
DNA in eukaryotic cells
1) In nucleus
2) Linear shape
3) Long molecule
4) tightly wound around the histone protein to fit in the nucleus as a chromosome
DNA in prokaryotic cells
-found freely in the cytoplasm ( within a region called nucleoid )
-not associated with histone proteins
-Shorter
DNA in mitochondria and chloroplasts
is like the DNA of prokaryotic cells, is short, circular,not membrane bound in a nucleus & not associated with proteins
define genome and proteome
Genome= The complete set of DNA (genetic material) in an organism
Proteome= The full range of proteins that a cell is able to produce
+why is the proteome larger than the genome+
due to the large amount of post translational modification of proteins (often in the Golgi apparatus) and
each gene is also capable of producing multiple different proteins via alternative splicing.
define genetic code
The genetic code is the sequence of base triplets (codons) in mRNA which code for specific amino acids.
features of the genetic code
Degenerate: multiple codons codes for a single amino acid
Non-overlapping: codons is only read once
Universal: each triplet codes for the same amino acid in all organisms.
how many triplets are there?
64
what does DNA code for?
the primary sequence of amino acids in a polypeptide
what codes for a specific amino acid?
a sequence of 3 bases - a triplet/codon
start codon
codes for the start of a polypeptide. is always the same triplet - methionine, AUG
what are stop codons?
triplets that mark the end of a polypeptide chain.
they do not code for amino acids
