4.1/2- EXAM Qs- DNA, Genes and Protein synthesis Flashcards
state one difference between the genome and proteome of a cell
-Genome is the complete set of genes in a cell
- the proteome is the full range of proteins that a cell can produce; [1 mark]
describe how the process of translation leads to the production of a polypeptide (4 marks)
Any four of the following:
- mRNA attaches to ribosome; [1 mark]
- codon on mRNA; [1 mark]
-binds to an anti-codon on tRNA; [1 mark] - each tRNA brings a specific amino acid; [1 mark]
- sequence of codons/bases on mRNA determines the order of amino acids; [1 mark]
- formation of peptide bonds OR amino acids joined by condensation reactions; [1 mark]
Messenger RNA (mRNA) is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus of a cell. (4 marks)
*Any four from: *
- Produced by transcription; [1 mark]
- Only one DNA strand acts as a template
OR antisense strand is the template strand; [1 mark]
-RNA nucleotides attracted to exposed bases; [1 mark]
- (Attraction) according to base-pairing rule OR complementary bases; [1 mark]
Adenine with uracil and cytosine with guanine OR uracil replaces thymine; [1 mark]
-Nucleotides added to the 3′ end of the RNA molecule
OR RNA molecule built in 5′ → 3′ direction; [1 mark]
-RNA polymerase bonds (RNA) nucleotides together OR RNA polymerase catalyses condensation reactions between (RNA) nucleotides; [1 mark]
- Pre-mRNA spliced to remove introns; [1 mark]
give two differences between the structure of mRNA and the structure of tRNA ( 2 marks)
Any two of the following:
- mRNA is longer OR mRNA has more nucleotides than tRNA; [1 mark]
- mRNA is a straight molecule OR tRNA is a folded molecule/clover-leaf shaped molecule; [1 mark]
- mRNA contains no paired bases/hydrogen bonds OR tRNA has some paired bases/hydrogen bonds; [1 mark]
describe the function of ribosomes in protein synthesis (4 marks)
Any four of the following:
- Translation/construction of polypeptide(s); [1 mark]
- Provide a binding site for mRNA OR mRNA attaches to ribosome; [1 mark]
- Provides binding sites for (two) tRNA molecules; [1 mark]
- Two amino acids are held close together; [1 mark]
- Formation of peptide bond(s); [1 mark]
(allows) assembly of amino acids into the sequence/primary structure; [1 mark]
[Total: 4 marks]
explain the role of transfer RNA (tRNA) in the process of translation ( 2 marks)
Any two of the following:
- tRNA attaches to (specific) amino acid; [1 mark]
- tRNA (with amino acid) moves to the ribosome; [1 mark]
- The anticodon of tRNA binds to/forms hydrogen bonds with (a complementary) codon of mRNA; [1 mark]
describe how a gene codes for a polypeptide (2 marks)
Any two of the following:
- DNA/the gene has a (specific) base sequence; [1 mark]
- The DNA base sequence determines the base sequence on (messenger) RNA; [1 mark]
- DNA base sequence, and therefore the mRNA base sequence determines the sequence of amino acids (in the polypeptide); [1 mark]
- Idea that three bases/a triplet on the DNA/mRNA code for one specific amino acid; [1 mark]
Compare the chemical structure of DNA and RNA nucleotides (2 marks)
DNA has deoxyribose sugar and/but RNA has ribose sugar; [1 mark]
DNA has the base T/thymine and/but RNA has the base U/uracil; [1 mark]
list the correct order to show the sequence of events during protein synthesis (4 marks)
F: The two strands of a DNA molecule separate
A: mRNA nucleotides join with exposed DNA bases and form a molecule of mRNA
D: The introns are spliced from the pre-mRNA to produce mRNA
G: The mRNA molecule leaves the nucleus
E: A ribosome attaches to the mRNA molecule
C: tRNA molecules bring specific amino acids to the mRNA molecule
B: Peptide bonds form between the amino acids
compare the structure of DNA with RNA (3 marks)
DNA: - double helix
-Thymine base
- Deoxyribose sugar
RNA: - single stranded
-Uracil base
- ribose sugar
Name and describe the features of the genetic code
Name 1 = Degenerate; [1 mark]
Description 1 = because there is more than one codon for (most) amino acids; [1 mark]
Name 2 = Triplet (code); [1 mark]
Description 2 = because three bases are needed to code for one amino acid; [1 mark]
Name 3 = Non-overlapping; [1 mark]
Description 3 = because the sequence is read so that each base is only part of one
codon/triplet; [1 mark]
distinguish between mitochondrial DNA and nuclear DNA of eukaryotic cells
- Mitochondrial DNA is short OR eukaryotic DNA is long; [1 mark]
- Mitochondrial DNA is circular DNA OR eukaryotic DNA is linear; [1 mark]
- Mitochondrial DNA is not associated with proteins OR eukaryotic DNA are associated with proteins (histones); [1 mark]
compare the sizes and structures of prokaryotic and eukaryotic chromosomes
Any four of the following:
- Prokaryotic chromosomes are generally smaller than eukaryotic nuclear chromosomes; [1 mark]
- e.g. the circular chromosome of E. coli, a prokaryote, is about 1.4 mm in circumference whereas a linear human chromosome may be 10–30 cm long; [1 mark]
- Prokaryotic chromosomes are circular, whereas eukaryotic nuclear chromosomes are linear; [1 mark]
- Prokaryotic chromosomes have a comparatively simple composition: DNA and some RNA whereas eukaryotic nuclear chromosomes are more complex: DNA, some RNA, and a lot of protein/histones; [1 mark]
- DNA in prokaryotic chromosomes do not have non-coding regions whereas the DNA in eukaryotic chromosomes have introns (non-coding DNA within genes) and non-coding multiple repeats between genes; [1 mark]
- Prokaryotic chromosomes and eukaryotic mitochondrial/chloroplast chromosomes are similar structures as both are short/circular/not associated with proteins; [1 mark]
(6 marks)
compare the DNA in prokaryotic cells with the DNA in the nucleus of eukaryotic cells
Any three of the following similarities:
- Nucleotide structure is identical (both have phosphate, deoxyribose and base); [1 mark]
- Nucleotides joined by phosphodiester bond; [1 mark]
- Both prokaryotic and nuclear eukaryotic DNA contain the same four bases - A, T, C, U; [1 mark]
- Both prokaryotic and nuclear eukaryotic DNA are made of triplet codons; [1 mark]
- Both prokaryotic and nuclear eukaryotic DNA is helical; [1 mark]
- Both prokaryotic and nuclear eukaryotic DNA is double stranded; [1 mark]
- Both prokaryotic and nuclear eukaryotic DNA code for the same amino acids; [1 mark]
Any three of the following differences:
- Prokaryotes have short DNA and eukaryotic nuclear DNA is long; [1 mark]
- Prokaryotes have circular DNA and eukaryotic nuclear DNA is linear; [1 mark]
- Prokaryotes have one molecule of DNA and eukaryotes have more than one; [1 mark]
- Prokaryotic DNA is not associated with proteins whereas eukaryotic nuclear DNA are (histones); [1 mark]
- Prokaryotic DNA does not have non-coding DNA regions whereas eukaryotic nuclear DNA has introns (non-coding DNA within genes) and non-coding multiple repeats between genes; [1 mark]
