DNA, Genes and Protein Synthesis Flashcards
What is a gene?
Section of DNA that contains the coded information for amino acid sequence for the making of polypeptides and functional RNA (rRNA and tRNA)
What are the 3 features of the genetic code?
Degenerate - each amino acid is coded for by more than one triplet
Universal - same sequence of bases that codes for the same amino acids
Non-overlapping - each base is only part of 1 triplet of bases that codes for 1 amino acid
How many amino acids that occur in proteins?
20
How many codes do:
-a pair of bases
-3 bases
produce?
Pair- 4 squared = 16
3- 4 cubed = 64
What are Exons?
Sequences that code for amino acids
What are Introns?
Separate exons and are non-coding sequences
What are the differences between DNA in a prokaryote and a eukaryote?
Prokaryotes: Shorter Circular Not associated with protein molecules Do not have chromosomes
Eukaryotes:
Longer
Linear
Associated with proteins called histones to form chromosomes
Mitochondria and chloroplasts contain DNA which is similar to prokaryotic DNA -> links to endosymbiotic theory
What is the structure of a chromosome?
2 chromatids held together by centromere
What are homologous chromosomes?
Two chromosomes that carry the same genes but not always the same alleles
What is an allele?
The number of alternative forms of a gene
Each person inherits one allele from each parent
What is a mutation?
Any change in the base sequence of a gene produces a new allele of the gene, resulting in new amino acids and as a result a different polypeptide, therefore a different protein
What is a codon?
Sequence of three bases on mRNA that codes for a single amino acid
What is a genome?
Complete set of genes in a cell
What is a proteome?
Full range of proteins produced by the genome
What are the two types of RNA important for proteins synthesis?
Messenger RNA
Transfer RNA
What is the structure of messenger RNA? + function
- Leaves through the nuclear pores
- Long straight chain of nucleotides
- Carries specific info of a protein
- Globular
What is the structure of transfer RNA? + function
- Clover leaf shape with amino acid and binding site
- Each tRNA is specific for one amino acid
- Has a sequence of 3 bases called an anti-codon which are complimentary to codons of mRNA molecule
What does a gene occupy?
A gene occupies a fixed position, called a locus, on a particular DNA molecule.
What is a start codon?
Indicates the start of gene
What is a stop codon?
End of sequence when 3 bases do not code for amino acid
What is the order of steps in protein synthesis?
DNA mRNA tRNA amino acid Polypeptide Protein
How does DNA make proteins?
- DNA provides instructions in form of bases
- Transcription, complimentary section of part of this base sequence is made in form of pre-mRNA
- pre-mRNA is spliced to form mRNA
- Translation, mRNA is used as a template to which complimentary tRNA molecules attach and amino acids that they carry are linked to form a polypeptide
What is transcription?
Transcription is the process of making pre-mRNA using part of DNA as a template
- DNA strands separate by RNA helicase
- Free nucleotides bind to one strand by specific base pairing
- U to A, C to G
- RNA polymerase joins nucleotides to form mRNA
What is the splicing or pre-mRNA?
in prokaryotes- transcription results in the production of mRNA from DNA
in eukaryotes- transcription results in the production of pre-mRNA, which is spliced to form mRNA
Splicing is the process of removing introns and joining exons
What is the structure of ribosomes?
- Large and small sub-units, mRNA passes through the middle
- 40% rRNA nd 60% proteins
- two sites for RNA attachment
What is translation?
Process of decoding mRNA into a polypeptide chain
- mRNA moves to ribosome
- Codon binds with complimentary anticodon on tRNA
- Each tRNA specific to one amino acid
- Peptide bonds form and join amino acids
