DNA & Protein synthesis study guide Flashcards
Describe the components of a nucleotide
Phosphate group, Pentose sugar (deoxyribose or ribose), and Nitrogen base (purine or pyrimidine)
Compare and Contrast DNA and RNA
Similarities
- both contain Adenine, Guanine, and Cytosine
- both contain a sugar-phosphate backbone
- both found in the nucleus
- both are composed of nucleotides
- both made up of a phosphate group, pentose sugar & a nitrogen base
- both have h-bonds between complementary base pairs
Differences
- RNA has Uracil & DNA has Thymine
- Double helix (DNA) & Single Strand (RNA
- 3 types of RNA, 1 type of DNA
- DNA large, RNA small
- A lot of RNA, little amount of DNA
- RNA found in cytoplasm and nucleus, DNA only found in nucleus
- DNA controls cellular activity and is hereditary material, RNA assists DNA make proteins
Which Nitrogen bases are pyrimidines? purines?
Adenine and Guanine (purine) Thymine and Cytosine (pyrimidine)
What is Chargaff’s rule and why is it important to the shape of DNA
The # of purine bases is equal to the # of pyrimidine bases ( purine bonds with pyrimidine and vice versa), With the help of this rule, one can determine the presence of a base in the DNA and also determine the strand length
Where does DNA replication occur
Nucleus
What enzymes are involved in DNA replication and what is each enzyme’s role?
helicase: ‘unzipping” the DNA
DNA polymerase: complementary base paring, proof reading.
What is Semi-Conservative replication
each new strand of DNA produced contains one old strand (the template) and one new strand
Explain the steps in DNA replication
- DNA is unzipped by helicase in the nucleus, unraveling the double helix structure.
- Then DNA polymerase does complementary base parings by bringing new nucleotides from the nucleolus. Nucleotides are attached by DNA polymerase to the leading strand (5’ to 3’) and to the lagging strand (3’ to 5’), but the lagging strand cannot continually keep add new nucleotides. So to fix that problem, nucleotides are added not by a fluid strand, but fragments (okazaki fragments) and to make a fluid strand, fragments are put together by ligase (glue).
- H-bonds form in between base pairs.
- Then, sugar-phosphate bonds form, creating the double helix structure
Functions of DNA/Chromosomes
DNA:
- controls cellular activities
- makes exact copies of itself
- undergoes mutations
- hereditary material
Chromosome:
- stores genetic information
Three types of RNA and their functions
mRNA:
- template strand for translation
tRNA:
- translates genetic info into protein sequences by delivering amino acids to ribosomes for protein synthesis
rRNA:
- makes ribosomes
What is Transcription, describe it and where does it occur
Transcription is the process of copying DNA into mRNA
It occurs in the nucleus
- DNA unzipped by RNA polymerase 1.
- RNA polymerase 2 starts RNA complementary base paring and brings in nucleotides associated with their respective base parings.
- RNA polymerase 2 zips the DNA back up and DNA’s h-bonds and sugar-phosphate bonds reform to revert it to a double helix structure.
- mRNA leaves the nucleus, via nuclear pores and enters the cytoplasm
Describe the process of translation: initiation, elongation and termination; where does it occur
initiation:
- the small ribosome subunit first attaches to start codon on mRNA.
- a tRNA with an anticodon complimentary base pairs with codon
- tRNA carries amino acid (methionine)
- tRNA requires ATP to pick up amino acids from cytoplasm
- large rRNA subunit then joins with small subunit
Elongation:
- a peptide bond is formed between new aa and first aa via dehydration synthesis
- aa is removed from tRNA1 (bond breaks between aa1 and tRNA1)
- tRNA1 is released, tRNA2 “shifts” over to the site previously occupied by tRNA1
- Ribosome moves over one codon along the mRNA (5’ to 3’)
- This movement shifts tRNA2 over (which is attached to growing amino acid chain)
- tRNA3 with aa3 can move on and bind with next codon on mRNA
- process repeats and chain elongates (10-20 aa form peptide bonds every second)
Termination:
- stop codon does not code for aa but act as a signal to stop translation
- protein called release factor binds to stop codon.
- The release factor causes a water molecule to be add the end of the polypeptide chain (hydrolysis) and chain then separates from the last tRNA
- protein is now complete
- mRNA is broken down by lysosome and ribosome dissociate in to its large and small subunits
- protein is sent to golgi body
-
During Translation, does the Ribosome move or mRNA
Ribosome
What is a mutation
A change that occurs when genetic info is damaged and alters the genetic message
What are four causes for mutations
- errors during DNA replication or cell division
- exposure to ionizing radiation.
- exposure to chemicals called mutagens
- infections by viruses
