Genes and chromosomes Flashcards
What is a gene?
A section of DNA at a locus ( a particular position)
This contains the coded information for making the amino acid sequences of polypeptides and functional RNA. This coded information is in the form of a specific sequence of bases along the DNA molecule
Describe what is meant by the degenerate code
- More than one triplet/ codon can code for the same amino acid
What is meant by the genetic code being universal
All species use the same 4 bases A,T,C,G and each base sequence codes for the same amino acid in all sequences
What is meant by the genetic code being non overlapping
Each base is only part of one triplet or one codon
Describe what an extron is
These are regions of the gene that are coding,
Each codon of an exon specifies a certain amino acid,
The sequence of codons in the exons determine the sequence of amino acids in a polypeptide
Describe what an intron is
Regions of the gene that do not contain codons that are needed to make the final protein
What is the difference between dna in eukaryotic cells and prokaryotic cells
In prokaryotic cells the DNA is short and circular and are not assosiated with DNA meaning they do not have chromosomes
In eukaryotic cells the DNA molecules are long and linear and are associated with histones to form chromosomes
Describe how the structure of a chromosome is formed
There is a DNA molecule and this is combined with protein molecules, then this DNA histone complex is coiled and this coils coil to form loops, then these loops coil and pack together to form chromosomes meaning alot of DNA can fit into one chromosome
What is an allele
One of a number of alternative forms of a gene, a different version of it. Each individual inherits an allele from each parent and they may be the same or different
Describe how a gene is the code for the production of a polypeptide
- This is a base sequence
- In triplets
- Which determines the specific amino acid sequence of a polypeptide
Define exon
A base sequence of DNA that codes for a specfic amino acid sequence
Describe how a phosphodiester bond is formed between two nucleotides in a DNA molecule
Condensaton, loss of water
Between the phosphate group of one nucleotide and the deoxyribose sugar group of the other nucleotide
Catalysed by DNA polymerase
Describe the difference in DNA between a plant cell and a prokaryotic cell
In a plant cell DNA is associated with histones to form chromsomes whereas in prokaryotic cell there are no histones involved
In a plant cell DNA may contain introns whereas in a prokaryotic cell they are no introns in DNA
In a plant cell DNA is linear whereas in a prokaryotic cell DNA is circular
No plasmids in plant cell whereas there are plasmids in prokaryotic cell
Define non coding base sequences and where are they positioned in genome
- They are sections of DNA which do not code for sequences of amino acids
- These are positioned in between exons
Differences between DNA in chloroplast and in DNA in the nucleus
- DNA in chloroplast has no introns whereas DNA in nucleus does
- DNA is chlorplast is linear whereas DNA its circular
- DNA in chloroplast is shorter and has fewer genes than DNA in the nucleus
Compare and contrast the DNA in eukaryotic cells to the DNA in prokaryotic cells
- Both have the same structure of nucleotide
- All nucelotides are joined by phosphodiester bonds in both
-Eukaryotic dna is longer
-Eukaryotic dna contains introns whereas prokaryotic doesnt - Prokaryotic cell contains DNA in plasmids
- Eukaryotic dna is linear, prokayotic is circular
-Eukaryotic cell dna is bound to histones whereas prokaryotic isnt
What is a homologous pair of chromosomes
A pair of chromosomes with the same genes at the same loci
What is the genome
All genes of an organism
What is the protenome
Range of proteins coded for by the genome
What is a gene
The sequence of DNA bases that codes for a polypeptide
