Protein Synthesis And DNA Flashcards
What is a gene?
A small section of DNA
How do genes control an organisms phenotype
Genes code for specific Amino acids to produce a specific protein/polypeptide
E.g enzymes that control biochemical reactions
Therfore control an organisms development and activities
Along with environmental factors genes determine phenotype
What determines an organisms phenotype?
Along with environmental factors genes determine phenotype
What is a locus
The position on the chromosome where a gene is found
What is a sequence of 3 bases on DNA called
Triplet
Describe the difference between intros and exons
Exons= expressed
Introns=not expressed
How many bases code for an Amino acid?
3
How did scientists conclude how many bases coded for an Amino acid?
If 1 base coded for 1 Amino acid there would be 4 Amino acids
If 2 bases coded for 1 Amino acid there would be 8 Amino acids
If 3 bases coded for 1 Amino acid there would be 64 Amino acids which are plenty to code for all 20 naturally occuring Amino acids
How many Amino acids are there
20
Do chloroplasts have more or less genes than mitochondria, why?
More because Photosynthesis requires more enzymes than Respiration
Enzymes are proteins that are coded for by genes
Name the main features of the genetic code
Degenerate
Non overlapping
Universal
What does degenerate code mean
One Amino acid can be coded for by various triplet codes
What does non overlapping mean
Every base is only read once
What is meant by a universal code?
Same triplets usually code for the same Amino acids in all organisms
How does the genetic code provide indirect evidence for evolution?
Universal code means there is a shared biochemistry so indirect evidence for shared ancestor
What does non functional DNA always start and end in?
Start with triplet coding for methanionine
End with stop codon
Compare where the genetic code if found in prokaryotes and eukaryotes
Pro= cytoplasm
Eu= nucleus
Compare the name of the molecule where the genetic code is found in prokaryotes and eukaryotes
Pro= nucleiod or plamsid
Eu= chromosome
Compare the shape of the genetic code found in prokaryotes and eukaryotes
Pro= circular
Eu= linear
Compare the association of proteins in the genetic code found in prokaryotes and eukaryotes
Pro=none
Eu= with histones
Compare the length of the genetic code found in prokaryotes and eukaryotes
Pro= short
Eu= longer
Compare the prevalence of Introns in the genetic code found in prokaryotes and eukaryotes
Pro= none
Eu= yes
Do prokaryotes have Introns?
No, only exons
Do the genes of chloroplast and mitochondria have Introns?
No, same a prokaryote
When are chromosomes visible
During semi-conservative DNA replication
What is the difference between sister chromosomes and homologous chromosomes?
Sister chromatids are genetically identical and joined by centro mere
Homologous pairs are not genetically identical and aren’t joined by a centromere
What phase of the cell cycle are chromosomes visible
Synthesis
What are sister chromatids?
Genetically identical arms of a chromosome
Describe how DNA is arranged
Double helix,
wound around histones (DNA histone complex)
Which are coiled and looped
Compact into a chromosome
Why are the numbers of chromosomes in organisms usually even
So that they can pair up for DNA replication
Define homologous chromosomes
Pair of chromosomes with the same genes at same locus but not genetically identical
One maternal one paternal
What is the diploid number
23 homologous pairs
What does n stand for in 2n
Haploid number
How is the diploid number represented algebraically
2n
What is the haploid number
23 chromosomes (not paired)
Why are gametes haploid
So that upon fertilización the diploid number is restored
What is an allele
A form of gene
How do mutations cause a different polypeptide to be synthesised?
Mutations cause a different base sequence creating different allele meaning different protein is coded for.
Define genome
Complete set of genes in a cell (including mitochondria)
Define proteome
Complete set of proteins able to be produced by a genome
Give difference between definition of proteome in proteome and complete proteome
Complete Proteome= proteins produced by specific cell under specific conditions
Proteome = complete set of proteins produced by a genome
Describe the structure of mRNA
Single stranded helix
Short
Polynucleotide polymer
What are codons
Three bases on a strand of MRNA
Why does MRNA need to be produced
Because DNA is too large to exit the nucleus
MRNA is able to diffuse out of the nucleus via a nucleur pore
Describe and explain the chemical stability of MRNA
Not very stable, no hydrogen bonds
Easily broken down
Prevents any unwanted protein Synthesis to reduce waste
Describe the structure of tRNA
Clover-leaf shape
Anticodon loop
One end of Polynucleotide chain extends beyond the other allowing for Amino acid attachment
Folds back on itself so has H bonds
How many TRNA molecules are there and why
64 to account for all 64 combinations of bases
What are the different types of RNA
TRNA-bring Amino acids to ribosome
MRNA- transfer genes for protein Synthesis
RRNA - make up ribosome
Order DNA MRNA and TRNA in increasing size
TRNA MRNA DNA
Define functional RNA
RNA not involved in protein Synthesis
What sugar is TRNA made of
Ribose
What is the func of MRNA
Act as scaffold and template for protein Synthesis
What is the func of TRNA
Carry Amino acids to ribosome
What determines the amount of TRNA and RRNA present in a cell
Metabolic activity
What enzymes are involved in transcription
DNA helicase
RNA polymerase
Describe how transcription occurs
DNA helicase breaks the hydrogen bonds between bases causing DNA to unwind and reveal template strand
Hydrogen bonds form between complementary bases on DNA and free RNA nucleotides (complementary base pairing).
RNA polymerase attaches to start of template and catalyses condensation reaction between RNA nucleotides to form phosphodiester bonds.
Pre-mRNA forms
RNA polymerase reaches stop codon and detaches
Splicing
Why are only 12 bases exposed at a time during transcription
DNA rejoins once RNA polymerase passes
Name the stages of protein Synthesis
Transcription
Translation
Describe how Splicing occurs
Introns are removed from PRE-MRNA forming mRNA
Why is only one Polynucleotide strand a template in transcription
RNA polymerase has specifically shaped active site so only moves in one direction down strand
Why is Splicing important
Without it a non-functional protein or no protein would be produced
State what is meant be translation
Synthesis of polypeptide chain
Describe translation
MRNA associates with ribosome so 2 codons are in ribosome
TRNA’s with complementary Anticodons form H bonds with codon on mRNA
Peptide bond forms between Amino acids on tRNA using enzymes and ATP in condensation reaction
Ribosome moves forward on codon repeating process as tRNA molecules are released
At stop codon release factor causes ribosome, tRNA and mRNA to detach.
Released polypeptide Folds and accosiates with prosthetic groups
What is a polysome
Multiple ribosomes working on a mRNA strand at once
Why do polysomes form?
Faster production of polypeptide
How can you tell where the start of an mRNA molecule is?
The longest polypeptide chain coming off a ribosome= near end
