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bio ppqs > Protein synthesis > Flashcards

Protein synthesis Flashcards

1
Q

Describe the role of a ribosome in the production of a polypeptide

(3 marks)

A
  • mRNA binds to ribosome
  • On two codons
  • Allows tRNA with anticodons to associate
  • Catalyses formation of peptide bonds between amino acids
  • Moves along mRNA
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2
Q

Use your knowledge of SC replication of DNA to suggest:
- The role of single-stranded DNA fragments
- The role of the DNA nucleotides

A

Single-stranded DNA fragments:
- Template
- Determines order nucleotides/ bases
Role of DNA nucleotide
- Forms complementary pairs/ strand

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3
Q

Give 2 features of DNA and explain how each one is important in SC replication

(2 marks)

A
  • Weak hydrogen bonds allow two strands to seperate
  • Two strands so both can act as templates
  • Complementary base pairing allows accurate replication and prevents mutation

(2 max)

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4
Q

Describe how a gene is a code for the production of a polypeptide

(3 marks)

A
  • Base/nucleotide sequence
  • In triplet
  • Determines order/sequence or amino acid/ primary structure
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5
Q

Define “non-coding base sequences” and descibe where the non-coding multiple repeats are positioned within the gene

(2 marks)

A
  • DNA that does not code for polypeptide/proteim/amino acids
  • Positioned between genes
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6
Q

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation.

(3 marks)

A
  • tRNA brings specific amino acid
  • Anticodon binds to codon
  • Amino acids join by condensation/ to form peptide bonds
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7
Q

Name the fixed position occupied by a gene on a DNA molecule

(1 mark)

A

Locus/ Loci

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8
Q

Give 2 reasons why a mutation in the base sequence of a gene may not cause a change in the structure of a polypeptide

(2 marks)

A
  • Triplets code for same amino acid/ degenerate
  • Occurs in introns
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9
Q

Give 2 reasons why a mutation in the base sequence of a gene may not cause a change in the structure of a polypeptide

(2 marks)

A
  • Triplets code for same amino acid/ degenerate
  • Occurs in introns
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10
Q

Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells

(5 marks)

A

Comparisons:
- Nucleotide structure is identical
- Nucleotides joined by phosphodiester bonds
Contrast:
- Eukaryotic DNA is longer
- Eukaryotic DNA contains introns, prokaryotic DNA does not
- Eukaryotic DNA is linear, prokaryotic DNA is circular
- Eukaryotic DNA is associated w histones, prokaryotic DNA is not

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11
Q

Suggest one way the structure of the chromosome could differ along its length to result in a stain binding more in some areas

(1 mark)

A
  • Differences in base sequence / supercoiling / histones
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12
Q

Give two structural differences between a molecule of mRNA and tRNA

(2 marks)

A
  • mRNA is linear, tRNA is a cloverleaf
  • mRNA does not have amino acid binding site, tRNA does
  • mRNA has more nucleotides
  • mRNAs have different lengths, all tRNAs are similar lengths
  • mRNA has codons, tRNA has anticodons
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13
Q

Define the term mutagenic agent

(1 mark)

A
  • A factor that increases the rate of mutations
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14
Q

Apart from mutation, explain one other way genetic variation within a species is increased

(2 marks)

A
  • Random fusion of gametes/ random fertilisation
  • Produces new allele combinations
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15
Q

Give two differences between meiosis and mitosis

(2 marks)

A

Mitosis vs meiosis
- One division vs 2 divisions
- Daughter cells genetically identical vs daughter cells genetically variable
- Two cells produced, vs four cells produced
- Diploid to diploid vs diploid to haploid
- Separation of homologous chromosomes only in meiosis
- Crossing over only in meiosis
- Independant segregation only in meiosis

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16
Q

Suggest and explain why offspring may be infertile

(2 marks)

A
  • Too many/ too few copies of chromosomes
  • Homologous chromosomes do not pair/ seperate
  • No meiosis

  • Too many or too few depends on context of question
17
Q

Give two reasons why offspring produced by meiosis are geneticall variable

(2 marks)

A
  • Independant segregation
  • Crossing over
18
Q

Explain how the chromosome no. is halved during meiosis

(2 marks)

A
  • Homologous chromosomes pair
  • One of each pair goes to each daughter cell/ opposite poles
19
Q

Describe the process of crossing over and explain how it increases genetic diversity

(4 marks)

A
  • Homologous pairs of chromosomes associate/ form a bivalent
  • Chiasmata forms
  • Equal lengths of non-sister chromatids/ alleles are exchanged
  • Producing new combinations of alleles
20
Q

Suggest why a scientist would take samples from a population at random

(2 marks)

A
  • Avoids bias
  • Results likely to be reliable/ repeatable
21
Q

Alcohol is toxic to fruit flies. Suggest and explain why the frequency of an allele that codes for the breakdown of alcohol increases over 45 generations

A
  • Flies with allele have selective advantage
  • So insects w allele are more likely to reproduce
  • Pass on allele
  • So allelic frequency increases
22
Q

What is a gene?

(1 mark)

A

A sequence of DNA bases that codes for a polypeptide

23
Q

A gene coding for an enzyme has two alleles, and one catalyses the breakdown of a molecule faster. Suggest why.

(3 marks)

(Part of an application question)

A
  • Different primary structure/ amino acid sequence
  • Different tertiary structure/ shape of active site
  • Enzyme-substrate complexes more likely/ more complementary
24
Q

Explain how two enzymes with different amino acid sequences can catalyse the same reaction.

(2 marks)

A
  • Both active sites have similar/ identical tertiary structures
  • Form enzyme-substrate complexes
25
Q

Describe how to make a 1 in 10 dilution, then use this to make a 1 in 100 dilution in a liquid culture of bacteria

(3 marks)

A
  • Add 1 part bacteria to 9 parts water
  • Mix well
  • Repeat using 9 parts of fresh water and 1 part 10^-1 dilution
26
Q

A student looked at cells in a 1 in 10 dilution and decided not to use this dilution to determine the number of cells in the undiluted liquid culture. Suggest why.

(2 marks)

A
  • Count unlikely to be accurate
  • Because too many cells
27
Q

Suggest and explain one reason why bacteria resistant to one antibiotic (Tetracycline) are more common that bacteria resistant to another (Streptomycin) in farm animals

(2 marks)

A
  • Tetracycline used in higher doses
  • Resistant bacteria more likely to survive
    OR
  • Higher frequency of mutations
  • So gene passed on to more bacteria
    OR
  • Tetracycline used over longer time period
  • More time for mutation/ selection to occur
28
Q

Lactase Persistence/ LP (the ability to continue producing lactase) is controlled by a dominant allele.

Describe how farming cattle as a source of milk could have led to an increase in LP.

(4 marks)

Summarised form of application question

A
  • LP due to mutation
  • Milk provides glucose/ galactose
  • Individuals with LP more likely to reproduce
  • Directional selection
  • Frequency of allele increases

(4 max)

29
Q

Lactase Persistence/ LP (the ability to continue producing lactase) is controlled by a dominant allele.

Use this information to explain why the number of people showing LP would rapidly increase once selection for this condition had been established

(2 marks)

Summarised form of application question, all nessecary info present

A
  • Dominant allele
  • Always expressed
30
Q

LP is caused by a mutation in DNA. This mutation does not occur in the gene coding for lactase.

Suggest and explain how this mutation causes LP

(2 marks)

A
  • Mutation in promoter for transcription factor
  • Lactase gene continues to be transcribed

bio ppqs (7 decks)

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