Protein Synthesis And Selection Flashcards
Differences between eukaryotic DNA and prokaryotic DNA
Eukaryotic is linear, contains introns, and associates with his tones
Prokaryotic is circular, doesn’t contain introns and isn’t associated with histones
Difference between DNA and RNA
DNA consist of phosphate groups, deoxyribose sugar and a base
RNA consists of phosphate group, ribose sugar, and a base (no thymine only uracil)
DNA vs mRNA
DNA
-double stranded
-Longer
-has thymine
-deoxyribose
-hydrogen bonds
-introns
-triplets
mRNA
-single strand
-shorter
-uracil instead of thymine
-ribose
-no hydrogen bonds
-no introns
-codons
What is a proteome
Full range of proteins a cell is able to produce
The genetic code is what 3 things
Universal - same 3 bases on mRNA code for the same amino acids in all organisms
Non- overlapping - each base is only part of 1 triplet
Degenerate - more than one triplet codes for one amino acid
Define the term exon.
Base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids/primary structure;
Describe Transcription in Eukaryotes
DNA helicase
1. Hydrogen bonds (between DNA bases) break;
2. (Only) one DNA strand acts as a template;
3. (Free) RNA nucleotides align by complementary base pairing;
4. (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
5. RNA polymerase joins (adjacent RNA) nucleotides;
6. (By) phosphodiester bonds (between adjacent nucleotides);
7. Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mRNA);
Describe Translation
- (mRNA attaches) to ribosomes OR (mRNA attaches) to rough endoplasmic reticulum;
- (tRNA) anticodons (bind to) complementary (mRNA) codons;
- tRNA brings a specific amino acid;
- Amino acids join by peptide bonds;
- (Amino acids join together) with the use of ATP;
- tRNA released (after amino acid joined to polypeptide);
- The ribosome moves along the mRNA to form the polypeptide;
Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA).
- mRNA does not have hydrogen bonds / base pairing, tRNA does; OR mRNA is linear / straight chain, tRNA is cloverleaf;
- mRNA does not have an amino acid binding site, tRNA does;
- mRNA has more nucleotides;
- (Different) mRNAs have different lengths, all tRNAs are similar / same length;
- mRNA has codons, tRNA has an anticodon;
What is an allele?
(Different) form/type/version of a gene / different base sequence of a gene;
Explain how selection occurs in living organisms
- Variation due to mutation;
- Different environmental/abiotic/biotic conditions / selection pressures;
- Selection for different/advantageous, features/characteristics/mutation/ /allele;
- Differential reproductive success / (selected) organisms survive and reproduce;
- Leads to change in allele frequency;
- Occurs over a long period of time;
Define degenerate code
More than one codon for one amino acid
Explain what the term non-overlapping DNA means.
A base from one triplet cannot be used in an adjacent triplet
A mutation in a gene coding for an enzyme
could lead to the production of a non-functional enzyme. Explain how
- Change in base sequence (of DNA/gene);
- Change in amino acid sequence / primary structure (of enzyme);
- Change in hydrogen/ionic/ disulphide bonds;
- Change in the tertiary structure/active site (of enzyme);
- Substrate not complementary/cannot bind (to enzyme / active site) / no enzyme-substrate complexes form;
Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why.
- Triplets code for same amino acid
- Occurs in introns /non-coding sequence;
Describe the role of ATP in the process of translation in protein synthesis
Releases energy
So peptide bonds form between amino acids
What is a substitution mutation
Is a silent mutation where the mutation does not change the amino acid if it is the third base substituted
First base substitution will change the amino acid sequence and therefore tertiary structure
Addition and deletion mutations
If nucleotide is added or deleted it results in alteration of base triplets from the mutation onwards
Reading frame shifts left or right. Known as frame shift
If occurs at end of gene it has a lesser effect
Define genetic diversity
The number of different alleles of genes in a population
What is stabilising selection
Occurs in a stable environment
Selection pressures at both ends of distribution curve
Favours the average
Eliminates extremes
Reduces variability
Reduces opportunity for evolutionary change
What is directional selection
Favours one extreme phenotype
What is disruptive selection
Opposite of stabilising selection
Selection pressures that favour the 2 extreme phenotypes
