Genetic control of protein Flashcards
Why is the transcribed mRNA strand shorter than the DNA template strand? (2)
- Introns are present in DNA.
- This is the non-coding part
Differences in structure between mRNA and tRNA (8)
mRNA vs tRNA::
- Linear and longer vs Clover leaf shape but shorter
- No binding site for amino acid vs Binding site present
- No H bonds vs H bonds present between nucleotides
- No anticodon region vs Anticodon region
Describe the role of tRNA in translation (3)
- anticodon must be complementary to codon for tRNA to read the message on mRNA
- tRNA carries specific amino acid to ribosome
- amino acids combine using ATP to form polypeptide;
Starting with mRNA in the nucleus, describe of protein is synthesised (8)
- mRNA leaves the nucleus through nuclear pore
- and goes to ribosome** in the **cytoplasm
- tRNA molecules bring amino acids to ribosome
- specific tRNA molecule for specific amino acid;
- anticodon of tRNA must be complementary to codon on mRNA;
- using ATP, peptide bonds form between amino acids;
- tRNA detaches and collects another amino acid;
- ribosome moves along mRNA;
Role of RNA polymerase (1)
- By forming phosodiester bonds, it attaches nucleotides, to form a mRNA strand
- checks and corrects mismatched base pairs
Examples of mutagenic agents
- uv light
- tobacco tar
Describe how an altered gene results in a different colour pigment in a plant. Enzymes involved (4)
- sequence of bases in mRNA would change;
- amino acids sequence different so different 1• structure
- this affects hydrogen bond formation
- so changes tertiary structure of enzyme so its active sites are changed
- relevant substrates can’t bind
Explain why the DNA base sequences of homologous chromosomes are almost the same (3)
- Homologous chromosomes have same genes;
- At the same loci;
- Different alleles usually have only a small differences in base sequence;
Describe how a new protein is made once a gene has been inserted into a cell (8)
- Unzipping of DNA by breaking hydrogen bonds;
- DNA helicase does this
- RNA nucleotides are attached by complementary base pairing
- RNA polymerase is used to make pre mRNA strand ;
- pre mRNA is spliced, removing introns
- mRNA enters ribosomes;
- Specific tRNA molecule associated with specific amino acid;
- Anticodon must be complementary to mRNA;
- Amino acids join by formation of peptide bonds;
- ATP is used to provide energy to do this;
- The gene has now been switched on;
Describe transcription (4)
- DNA helicase cause the DNA strands separate;
- The exposed strand acts as a template
- Free nucleotides bind to one strand by complementary base pairing (U-A) (G-C)
- RNA polymerase joins nucleotides to form pre mRNA;
Describe the features of a gene which enable it to code for a particular protein (8)
- Gene is a section** of DNA which consists of a sequence of **bases
- code read in threes;
- Triplet codes for 1 amino acid, which combine to form a polypeptide;
- Degenerate code;
- non-overlapping;
- start/stop codes present;
Differences and similarites between DNA and RNA (7)
Similarities :
- both have phosphate
- AGC in common
- pentose sugar;
Differences:
- DNA has deoxyribose whereas RNA has ribose;
- DNA thymine, RNA Uracil
- DNA double stranded, RNA single stranded;
- DNA longer;
- Only one type DNA, RNA 3 types: mRNA,tRNA, rRNA
Differences and similarites between DNA replication and transcription (8)
Similarities:
- DNA acts as template;
- Both involve polymerase enzyme;
- Complementary base pairing
Differences:
- All of DNA is copied whereas only a section copied in transcription ;
- one strand used transcription, two in replication;
- enzymes that are different, D(R)NA polymerase
Why is only 1% of our genetic information transcribed into functional RNA sequences? (4)
- Only some genes switched on;
- different proteins and enzyme are required by different cells;
- some DNA does not codes (introns)
- Repeated DNA (stutter sequences)
Describe the structure of tRNA (4)
- Consists of 1 polynucleotide
- Hydrogen bonds are present inbetween the bases
- Anticodon region
- Amino acid attachment region
- Clover shape
Why does addition and deletion result in an non-functional protein being formed?
- A nucleotide is added or deleted
- Causes frame shift
- DNA triplets after point of mutation are altered
- so mRNA codons after point of mutation altered
- Different sequence of amino acids in polypeptide so primary structure different;
- this affects hydrogen bond formation
- Alters tertiary structure of protein
Degenerate code definition (1)
- One amino acid can be coded for by more than one triplet;
Define codon (2)
- 3 bases on DNA;
- That code for an amino acid;
Explain why knowing the DNA sequence of exons, but not introns is useful in ascertaining mutations (4)
- Introns not translated
- Exons code for amino acids
- Mutations of exons affect amino acid sequences;
- This leads to a change in tertiary structure so a faulty protein is made
Why are the proportions of bases in the middle section of a chromosome different to that of the end
- Different genes;
- Have different base sequences
Even though the base sequence changes, why can the same amino acid sequence be the same
- Genetic code degenerate;
- Mutation in intron;
Why does a mutation of a tumour suppressor gene result in a tumour
- Tumour suppressor gene inactivated
- So not able to control cell division
- Rate of cell division too fast
How can smoking cause tumours
- Contains carcinogens** which causes **mutation;
- Of genes controlling cell division;
- Tumour suppressor genes inactivate;
- Causes protooncogenes to mutate into oncogenes;
- Leads to uncontrolled cell division
What is a transcription factor?
- Protein that moves from cytoplasm to DNA;
- and binds to promoter;
- which leads to mRNA production
