DNA, Genes And Protein Synthesis Flashcards
Describe the nature of a gene
A gene is a section of DNA that contains coded information for making polypeptides and functional RNA.
Explain how genes code for polypeptides
The bases in the gene provide a triplet code for amino acids. Three bases is a triplet which provides a code from one amino acid. Most amino acids are coded for by more than one triplet. The code is non-overlapping, meaning each base is read once only in a sequence.
Distinguish between the DNA in prokaryotic cells and the DNA in eukaryotic organisms
In prokarytotic cells DNA is shorter and forms a circle. It is not associated with proteins, so no chromosomes are present. In eukaryotic cells DNA is longer, linear and associated with proteins called histones which enable formation of chromosomes.
Describe the structure of a chromosome
The DNA double helix is wound around histones forming a DNA histone complex. This is coiled, then looped and coiled again to form a chromosome. Chromosomes are formed of a single strand of DNA.
Explain how genes are arranged in a DNA molecule
Each DNA molecule has many genes along its length, and each gene occupies a specific position (the locus) on the DNa molecule.
Describe the nature of homologous chromosomes
A pair of chromosomes which carry the same genes (but not necessarily the same alleles), one from the female gamete and one from the male gamete.
-total number of homologous pairs = diploid number
Explain what is meant by an allele
Different forms of the same gene, which code for different polypeptides
what does changes in base sequence of gene produce
-new allele of that gene = mutation
-resulting in different a.a sequence being coded for
-different a.a sequence will lead to production of diff polypeptide and hence diff protein
- protein may not function propely
Define the terms genome and proteome
Genome is the complete set of genes in a cell (including in mitochondria and chloroplasts). Proteome is all the proteins provided by the genome.
Define the terms genome and proteome
Genome is the complete set of genes in a cell (including in mitochondria and chloroplasts). Proteome is all the proteins provided by the genome.
Describe the structure of ribonucleic acid (RNA)
RNA is made up of nucleotides formed of ribose (a pentose sugar), organic bases- A, G, C and U (uracil), and a phosphate. The sequence of bases are called codons.
Describe the structure and the role of messenger RNA (mRNA)
mRNA is a long strand in a single helix. It acts as a template for protein synthesis. The sequence of bases determines the amino acid sequence. Codons provide the codes for individual amino acids.
Describe the structure and role of transfer RNA (tRNA)
tRNA is a small molecule made of around 80 nucleotides. It is single stranded, but folded into a clover shape. tRNA molecules bind to specific amino acids. It has an anticodon which is complenetary to the codon on the mRNA.
Explain how pre-messenger RNA is produced from DNA in the process called transcription
RNA polymerase separates the two strands of the DNA helix by breaking the hydrogen bonds between DNA nucleotides.
RNA polymerase adds RNA nucleotides which are complementary to the nucleotides of one DNA strand.
RNA sugar-phosphate backbone forms to form a pre-mRNA strand
Describe how the pre-messenger RNA is modified to form mRNA
pre-mRNA undergoes splicing which removes the non-coding sections of mRNA called introns. Introns are removed, exons remain and an mRNA molecules is formed.
