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
