Exam Questions Flashcards
(42 cards)
Describe how a gene is a code for the production of a polypeptide. Do not include information about transcription or translation in your answer.
- Because the nucleotide sequence
- In triplets
- Determines the primary structure of the polypeptide.
What part of the cell cycle are mutations most likely to occur?
S phase
It is the longest phase.
Define the term ‘exon’.
Triplet sequence coding for the primary structure of a polypeptide.
What are 3 differences between prokaryotic DNA and eukaryotic DNA?
- Eukaryotic DNA is linear, prokaryotic DNA is circular.
- Eukaryotic DNA has introns, prokaryotic DNA has no introns.
- Eukaryotic DNA is longer, prokaryotic DNA is shorter.
Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome.
- DNA that doesn’t code for proteins.
- Positioned between genes.
Give three ways in which the DNA in a chloroplast is different from DNA in the nucleus.
- DNA in chloroplasts is shorter.
- DNA in chloroplasts has fewer genes.
- DNA in chloroplasts is circular.
Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why
- Genetic code is degenerate.
- Occurs in introns.
Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells.
- Nucleotide structure is identical.
- Nucleotides are joined by phosphodiester bonds.
- DNA in chloroplasts is similar to prokaryotic DNA.
- Eukaryotic DNA is longer.
- Eukaryotic DNA contains introns.
- Eukaryotic DNA is linear.
What is a homologous pair of chromosomes?
Two chromosomes that carry the same genes.
Describe four differences between the structure of a tRNA molecule and the structure of an mRNA molecule.
- tRNA is a clover leaf shape, mRNA is linear.
- tRNA has an amino acid binding site, mRNA doesn’t.
- tRNA has anticodon, mRNA has codon.
- tRNA has hydrogen bonds, mRNA doesn’t.
Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation.
- tRNA brings a specific amino acid to the ribosome.
- Anticodon on tRNA binds to codon on mRNA.
- Amino acids join by condensation reaction using ATP.
Describe how mRNA is produced from an exposed template strand of DNA.
- Free RNA nucleotides form complementary base pairs.
- Phosphodiester bonds form.
- By action of RNA polymerase.
Describe how mRNA is formed by transcription in eukaryotes.
- DNA helicase breaks hydrogen bonds between DNA bases.
- One strand of DNA acts as a template.
- Free floating RNA nucleotides align by complementary base pairing.
- RNA polymerase joins adjacent nucleotides.
- Phosphodiester bonds form between adjacent nucleotides.
- Pre-mRNA is spliced to form mRNA.
Describe how a polypeptide is formed by translation of mRNA
- mRNA attaches to ribosomes.
- tRNA anticodons bind to mRNA codons.
- tRNA brings a specific amino acid.
- Amino acids join by condensation reaction using ATP to form peptide bonds.
- tRNA released after amino acid joins to polypeptide.
- The ribosome moves along the mRNA to form the polypeptide.
What is meant by the genetic code being degenerate?
- More than one codon codes for a single amino acid.
Describe the role of a ribosome in the production of a polypeptide. Do not include transcription in your answer.
- mRNA binds to ribosome.
- Allows tRNA with anticodons to bind.
- Catalyses formation of peptide bond between amino acids.
Define the term mutagenic agent
A factor that increases the rate of mutations.
Apart from mutation, explain one other way genetic variation within a species is increased.
- Random fertilisation
- Produces new allele combinations.
Give two reasons why trout eggs produced by meiosis are genetically different.
- Crossing over
- Independent Segregation
The offspring produced from farmed trout are sterile. Suggest and explain why.
- Extra set of chromosomes.
- So homologous pair of chromosomes don’t separate evenly.
- So no meiosis.
Define ‘gene mutation’ and explain how a gene mutation can have:
* no effect on an individual
* a positive effect on an individual.
- Change in the nucleotide
- Resulting in the formation of a new allele
- Has no effect because - the genetic code is degenerate. It could change the amino acid but will have no effect on the tertiary structure.
- Has a positive effect because - Results in change in polypeptide that positively changes the properties of the protein. May result in increased chances of survival.
Give five differences between mitosis and meiosis
- Mitosis is one division - meiosis is two.
- Mitosis creates genetically identical daughter cells - meiosis creates genetically different daughter cells.
- Mitosis creates 2 daughter cells - meiosis creates 4 daughter cells.
- Crossing over and independent segregation only occur in meiosis.
- Separation of homologous chromosomes only occurs in meiosis.
Explain how the chromosome number is halved during meiosis
- Homologous chromosomes.
- One of each pair goes to opposite poles.
Describe the process of crossing over and explain how it increases genetic diversity
- Homologous pairs of chromosomes form a bivalent.
- Chiasmata form.
- Alleles are exchanged.
- Producing new combinations of alleles.
