Key Area 1.3 Flashcards
What determines the phenotype of an organism
Proteins
The processes of gene expression are?
Transcription
Translation
What are proteins made of
Amino acids
What type of chain is formed when amino acids link together
Polypeptide chain
What type of bond links amino acids together
Peptide bonds
Why is the shape of a protein important
Allows it to carry out its function
How are long chains of amino acids able to form into 3D proteins
Hydrogen bonds form in certain places in the chain allowing them to be folded
What name is given to the point hydrogen bonds form in a polypeptide chain
Cross connections
What is the difference between RNA and DNA
RNA:
Single stranded
A-U C-G
Ribose sugar
DNA:
Double stranded
A-T C-G
deoxyribose sugar
Name and describe the types of RNA
mRNA: carries a copy of the DNA code from the nucleus to the ribosomes
tRNA:collects amino acids and bring them to the ribosomes to build proteins
rRNA: combines with proteins to create the ribosome
Where does does transcription take place
Nucleus
Name the enzyme involved in transcription and state it’s function
RNA polymerase: it forms the bonds between the nucleotides to form a mRNA strand
Describe the process of transcription
1) a section of DNA unwinds and weak hydrogen bonds between bases are broken, separating the strand
2) free RNA nucleotides align themselves with their complementary base pair (A-U C-G)
3) RNA polymerase forms the bonds between the sugar of one RNA nucleotide to the phosphate of the next
4) nucleotides continue to be added until that section has been transcripted. This strand is called the primary transcript
5) the primary transcript peels away from the DNA and the DNA recoils
6) primary transcript undergoes mRNA splicing and becomes a mature transcript
7) the mature transcript leaves the nucleus through nuclear membrane pores and enters the cytoplasm where it attaches to a ribosome
What are introns and exons
Introns - non coding regions
Exons - coding regions
What is alternative mRNA splicing and why it it advantageous
Alternative mRNA splicing is the process by which different regions can be treated as exons or introns depending on the protein being made
Advantageous:
This allows more than one protein to be made from a single gene
Describe how a mature mRNA transcript can be achieved
It is formed through mRNA splicing
Different parts of the primary transcript are treated as exons and introns
The introns are removed and the exons are spliced together to form a continuous sequences
This is now called the MATURE TRANSCRIPT
The mature transcript leaves the nucleus and travels to the cytoplasm
What is a group of 3 bases on an mRNA strand called
What is a group of 3 bases on an tRNA molecule called
1) codon
2) anticodon
Where does translation take place
The ribosomes
Describe the process of translation
1) Ribosomes bind to the 5’ end of the mRNA strand so that the start codon is at the attachment site
2) tRNA molecule with complementary anti-codon brings the specific amino acid to the ribosome
3) anti-codon and codon align and a weak hydrogen bond it formed between the two
4) ribosome moves along and reads next codon and the complementary tRNA molecule carrying the specific amino acid aligns next to the codon
5) peptide bond firms between the amino acids and tRNA molecule are released to be reused
6) the process continues until stop codon is reached
7) finally the polypeptide chain folds to become a protein
State and describe two ways polypeptides can be altered after translation
Cleavage: can be cut by an enzyme to make it active
Addition of other molecules:
Carbohydrates and phosphate groups
What allows a single gene to be expressed a several proteins m
Alternative mRNA splicing and post translational modification
