Topic 4A: DNA, RNA and Protein Synthesis Flashcards
1
Q
What is a genome?
A
- Complete gene set in a cell
2
Q
What is a proteome?
A
- Full range of proteins a cell can produce
3
Q
How is DNA stored in eukaryotic cells?
A
- In the nucleus
- Long, linear
- Coiled using histone proteins to form chromosomes
4
Q
How is DNA stored in prokaryotic cells?
A
- Short, circular
- Coiled - condenses by supercoiling
- No histones
- No introns
5
Q
How is DNA stored in mitochondria and chloroplasts?
A
- Similar to in prokaryotes
- Circular, shorter
- No histone proteins
6
Q
What are genes?
A
- Sequence of DNA bases coding for a polypeptide or functional RNA
- 3 bases code for an amino acid and sequence dictates primary structure
7
Q
What are introns?
A
- Non-coding regions
8
Q
What are exons?
A
- Coding regions of DNA
9
Q
What are multiple repeats?
A
- Outside of genes
- Sequences of repeating bases
- Do not code for things
10
Q
What are alleles?
A
- Different form of a gene
- Slightly different order of bases
- Produce slightly different versions of a polypeptide
11
Q
What are homologous chromosomes?
A
- Pairs of matching chromosomes
- Same size
- Same genes but can have different alleles
- Genes for same characteristic found on fixed points - loci
12
Q
Why is DNA described as degenerate?
A
- There are more possible triplet combinations than there are amino acids to code for
- 64 combinations, 20 amino acids
- Some amino acids are coded for by multiple triplets
13
Q
How is DNA non-overlapping?
A
- Base triplets do not share bases
- Each are read in sequence, separate from the triplet before and after
14
Q
How is DNA universal?
A
- Same base triplets code for amino acids in all organisms
- Transferable
15
Q
How is mRNA structured?
A
- Single polynucleotide strand
- Has groups of three bases - codon
16
Q
How is mRNA made / needed?
A
- Made in transcription to move genetic information from nucleus to ribosome
17
Q
How is tRNA structured?
A
- Single polynucleotide strand
- Folded into a clover shape
- Hydrogen bonds between specific base pairs hold the shape
- 3 bases on one end - anticodon
- Amino acid binding site on other end
18
Q
Describe the stages if transcription.
A
- DNA unwinds as DNA helicase breaks H bonds and bases are exposed
- RNA nucleotides line up with complimentary base pairs as one strand acts as a template (A-U)
- RNA polymerase joins the nucleotides together with phosphodiester bonds
- RNA polymerase moves down, assembling the mRNA
- H bonds form in the DNA once RNA polymerase moves on and it recoils
- When the stop codon is reached, RNA polymerase detaches and mRNA is made
19
Q
What is splicing?
A
- In eukaryotes, introns and exons copied to make pre-mRNA
- Introns removed (spliced) and exons joined to form mRNA
- mRNA leaved nucleus via nuclear pores
20
Q
How is mRNA modified in prokaryotes and why?
A
- No modification needed
- No introns present
21
Q
Describe translation
A
- mRNA attaches to ribosome at start codon
- tRNA with complimentary anticodon binds to first triplet and another binds to the second triplet
- Amino acids attached to tRNA are joined by peptide bonds - needs ATP and an enzyme
- First tRNA moves away leaving the amino acid behind
- Ribosome then moves down and next tRNA can bind
- Process continues until stop codon is reached and ribosome detaches leaving the amino acid chain
