Chapter 8 - DNA, Genes and Protein Synthesis Flashcards
What is a gene, and its locus?
A gene is a section of DNA which codes for a specific protein (more specifically its amino acid sequence), and its locus is specifically where on the chromosome it is found. They can also code for functional RNA, such as ribosomal RNA or tRNA
What can cause genetic diversity within species?
Gene mutation, chromosome mutation or other factors assosciated with meiosis and fertilisation
How can variation within a species be measured?
By looking at the base sequence of DNA, or the amino acid sequence of specific proteins
How is DNA arranged in prokaryotes?
In short, circular loops which aren’t assosciated with proteins
How is DNA arranged in eukaryotes?
It is within a nucleus, longer and each DNA molecule is assosciated with proteins (histones) - which together form a chromosome
What else within eukaryotes contains DNA?
Mitochondria and chloroplasts have their own DNA which is like prokaryotic DNA (small, circular and not protein assosciated)
What does the “triplet” mean?
It is the fact that three DNA bases code for one amino acid
How is the nature of the triplet code described, and what does it mean?
It is universal (the same across all organisms on the planet), non-overlapping (meaning the three bases used for one codon are only used for that codon, and are not part of another codon) and degenerate (because each amino acid does have several different combinations of amino acids which can code for it, minimising the impact of mutations)
Do all of the bases in eukaryotic DNA code for polypeptide seqeunces?
No, there are often repeat regions between functional genes, as well as activated regions for transcription factors. Furthermore, even genes have exons (functional codons) and introns within each DNA sequence
What is the difference between a genome and a proteome?
A genome is the full set of genes in a cell, whereas a proteome is all of the proteins that a cell is able to make
What is the structure of a molecule of mRNA?
It is a single strand made up of uracil, thymine and of cytosine, guanine. Another difference comes from the backbone, which is made of ribose sugar as opposed to deoxyribose.
How is mRNA formed?
The free RNA nucleotides will complementary base pair to the exposed DNA strand (after DNA helicase) to form an mRNA sequence, where phosphodiester bonds are formed by RNA polymerase
What happens to mRNA after its bonds are formed?
As it goes to leave the nucleus, spliceosomes remove the introns from the exons, resulting in mature RNA. Then, the RNA sequence will go to the rough ER and its ribosomes, where translation will begin
What is the difference between mRNA in prokaryotes and eukaryotes?
mRNA in eukaryotes is spliced then translated, whereas in prokaryotes it is immediately translated
What is tRNA?
tRNA is a molecule of RNA which has an anti-codon on one side and is shaped like a clover leaf. The anti-codon is specific to an amino acid.
