MSP - nucleotides and protein synthesis

what are the components of a nucleotide?

• phosphate group

• pentose sugar

• nitrogen base

describe how DNA is formed and stored in the nucleus

• complementary bae pairing of DNA holds the 2 DNA strands in the DNA molecule together

• DNA molecule twists into a DNA helix

• DNA helix coils around proteins called histones

• the DNA and histones form chromatin

• chromatin coils into a chromatid which is copied, forming a second chromatid

• the 2 chromatic are joined together with a centromere

• chromosomes are found in the nucleus

what is RNA? what are the types of RNA?

• RNA ia a single, shorter polynucleotide chain with ribose pentose sugar and a uracil base instead of thymine

• mRNA - messenger - transfers genetic information from DNA to ribosomes, made in transcription

• tRNA - transfer - used in translation

describe the structure of an mRNA molecule

• long single strand, no H bonds

• complementary to the template DNA strand

• contains codons

what is a codon?

three nucleotide bases on mRNA that code for an amino acid

describe the structure of a tRNA molecule

• forms a clover-leaf shape, held by H bonds

• one end attaches to a specific amino acid

• other end has a specific anti-codon

what is a anti-codon?

three nucleotide bases on tRNA which are complementary to the codon on mRNA

what is transcription and what are the two stages?

the process of reading the template strand of DNA and creating a complementary strand of mRNA

1. transcription

2. splicing

describe the process of transcription

1. DNA helicase unzips the DNA by breaking the H bonds, exposing the template strand

2. RNA nucleotide attach to the exposed bases through complementary base pairing

3. RNA polymerase joins the RNA nucleotides together by forming phosphodiester bonds

4. this forms a molecule of pre-mRNA

describe the process of splicing

1. pre-mRNA contains coding regions called exons and non-coding regions called introns

2. introns are removed in a process known as splicing

3. this is done by a spliceosome

4. exons are joined back together to form mRNA

describe the process of translation

1. mRNA leaves the nucleus and attaches to a ribosome at the start codon

2. tRNA molecules carry a specific amino acid

3. tRNA have an anticodon that binds to the mRNA codon

4. the ribosome moves along the mRNA and a new tRNA molecule with a new amino acid binds to the next codon

5. a peptide bond forms between the amino acids

6. the tRNA molecules detach and collect new amino acids

7. the process repeats until the stop codon is reached

8. a polypeptide is formed

what is a mutation?

mutations are changes to the DNA sequence that affect the structure of the protein produced

what are the three ways in which NA can be described?

1. universal - all organisms have the same genetic code

2. degenerate - more than one codon can code for the same amino acid

3. non-overlapping - each base is only used in one codon

what are the three types of mutation?

1. substitution - when one DNA base is swapped for another

2. addition - when a DNA base is added

3. deletion - when a DNA base is removed

how does a mutation effect the functioning of a protein??

1. mutation causes a change in the DNA sequence

2. the gene is transcribed into mRNA with different codons

3. tRNA brings different amino acids o the ribosome during translation

4. the sequence of amino acids is different so the primary structure of the protein is different

5. the protein is unable to bind where it is supposed to

6. protein cannot perform its function