DNA, Replication and Protein Synthesis Flashcards Preview

Human Bio- Unit 1 > DNA, Replication and Protein Synthesis > Flashcards

Flashcards in DNA, Replication and Protein Synthesis Deck (36):

Describe the structure of DNA.

Double stranded helix with a sugar phosphate backbone. Each strand is made up repeating units called nucleotides. These bases are held together by weak hydrogen bonds.


What does a nucleotide consist of?

A deoxyribose sugar, phosphate and a base.


Describe DNA replication.

Double helix unwinds- weak hydrogen bonds break causing the 2 stands to separate- free DNA nucleotide join complementary pair on open strand- hydrogen bonds reform- newly formed daughter DNA begins to wind into double helix.


Semi-conservative replication

Replication results in 2 new DNA molecules and it is said to be semi-conservative because each new DNA molecules receives one strand of the original parent molecule.


The leading strand.

Builds up continuously in the direction 5'-3' towards the unzipping point. DNA polymerase attaches nucleotides to the 3' end of the DNA strand.


The lagging strand.

Can only be built away from the unzipping point 5'-3'. Replicated in Okazaki fragments which are 'glued' together with the enzyme DNA ligase.


What enzymes unravels the double helix?



Why is a primer needed in DNA replication?

To initiate DNA replication. DNA polymerase requires a primer to start the replication process.


What does DNA require for replication?

DNA, enzymes, ATP and free nucleotides.


What is RNA?

A second type of nucleic acid that is involved in copying DNA and changing its code into a protein.


What are the 3 main differences between DNA and RNA?

RNA has one strand and DNA has 2.
Complementary base pair of RNA is uracil.
Sugar present in RNA is ribose, not Deoxyribose.


What is transcription?

The synthesis of mRNA from a section of DNA.


What is RNA Polymerase?

The enzyme responsible for transcription as it moves along the gene, unwinding and opening the DNA strand. Also forms the mRNA strand by joining nucleotides together.


What are the 2 types of RNA?

Messenger RNA (mRNA) and transfer RNA (tRNA).


What is mRNA?

Formed inside the nucleus from free nucleotides and carries a copy of the DNA code from the nucleus to the ribosome.


What are the 2 types of ribosome?

Floating freely or attached to the rough endoplasmic reticulum.


Free floating ribosome.

Used to synthesise proteins for use within the cell.


Rough endoplasmic reticulum (ER) ribosome.

Synthesise proteins for export or inclusion in the membrane.


Role of the tRNA.

Carry a specific amino acid to the ribosome for attachment to the peptide chain.


Transcription of DNA into an RNA molecule.

RNA polymerase unwinds DNA helix- Primary transcript of RNA is synthesised from RNA nucleotides by complimentary base pairing- Hydrogen bonds are reformed- Covalent bonds from between the new RNA nucleotides which allows a new strand to be formed- Hydrogen bonds break between DNA and RNA allowing mRNA to break from DNA template- mRNA undergoes splicing- leaves the nucleus through a pore into cytoplasm.


What is translation?

The process in which a polypeptide is synthesised from an mRNA template.


Translation of mRNA into a polypeptide.

tRNA folds due to base pairing to form a triplet anticodon site and an attachment site for a specific amino acid- it then attaches to the codon on the mRNA were weak hydrogen bonds are formed to from an amino acid- amino acids join to form a polypeptide chain.


What are stop codons?

Translation continues until mRNA codons UAA, UAG and UGA are reached- these do not code for amino acids and act as stop codons.


What are start codon?

mRNA codons AUG complementary to tRNA anticodon UAC codes for the amino acid methionine (met) and acts as a start codon.


What is an exon?

A coding region of the primary transcript that carries the code for a protein to be transcribed.


What is an intron?

Introns are non-coding sequences and during RNA splicing they are cut out and the exons are spliced together to form the mature RNA transcript.


Post translation modification of a protein.

May include:-
Cutting and combining polypeptide chains.


What is phosphorylation?

Adding phosphates to the protein. KINASE enzymes add phosphate groups. PHOSPHATE enzymes remove phosphate groups.


What is glycolysation?

Adding carbohydrates such as sugars to the protein.


Protein primary structure.

The primary structure of the protein is the polypeptide chain of amino acids.


Protein secondary structure.

Weak hydrogen bonds form between various amino acids. This causes the polypeptide chain to become coiled or folded into a BETA pleated sheet.


Protein teritary structure.

The final structure of the protein due to the hydrogen bonding and sulphide bonding between amino acids. Form either FIBROUS or GLOBULAR proteins.


Protein quarternary structure.

Formed when many polypeptides become bonded together- other elements are also added.


Fibrous protein.

Long parallel strands. Collagen, keratin, actin and myosin.


Globular protein.

Tangled ball. Enzymes, hormones and antibodies.


Conjugated protein.

Contains polypeptide chains and a non-protein part
i.e. haemoglobin consists of 4 polypeptide chains and 4 iron chains.