Genetic information, variation & relationships Flashcards

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1
Q

Define the term exon.

A

Base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids/primary structure;

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2
Q

Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA). [2]

A
  • mRNA does not have hydrogen bonds / base pairing, tRNA does; OR mRNA is linear / straight chain, tRNA is cloverleaf;
  • mRNA does not have an amino acid binding site, tRNA does;
  • mRNA has more nucleotides;
  • (Different) mRNAs have different lengths, all tRNAs are similar / same length;
  • mRNA has codons, tRNA has an anticodon;
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3
Q

What is an allele?

A
  • (Different) form/type/version of a gene

OR

  • different base sequence of a gene;
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4
Q

What is a gene?

A
  • A sequence of DNA (nucleotide) bases that codes for a (specific) polypeptide;
  • ‘codes for a functional RNA’
  • ‘codes for rRNA/tRNAs’
  • ‘codes for a sequence of amino acids/primary structure’
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5
Q

What is a TRIPLET?

A

A sequence of 3 DNA (nucleotide) bases

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6
Q

What is a CODON?

A

A sequence of 3 mRNA (nucleotide) bases

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7
Q

What is an ANTICODON?

A

A sequence of 3 tRNA (nucleotide) bases that is complementary to a specific codon.

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8
Q

If a DNA sequence is:
TAG.GCG.AAT.CCG

What is the mRNA sequence?

A

AUC.CGC.UUA.GGC

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9
Q

Describe the structure of DNA and the structure of a chromosome. [5]

A
  1. Polymer of nucleotides; Accept ‘polynucleotide’
  2. (Nucleotide) consists of deoxyribose, phosphate and an organic/nitrogenous base;
  3. Phosphodiester bonds (between nucleotides);
  4. DNA double helix held by H bonds OR 2 strands held by H bonds;
  5. (Hydrogen bonds/pairing) between adenine, thymine and cytosine, guanine;

Reject adenosine and cysteine

  1. DNA is associated with histones/proteins;
  2. (During mitosis/when visible) chromosome consists of two chromatids joined at a centromere;
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10
Q

Describe Transcription in Eukaryotes [5]

A
  • Hydrogen bonds (between DNA bases) break;
  • (Only) one DNA strand acts as a template;
  • (Free) RNA nucleotides align by complementary base pairing;
  • (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
  • RNA polymerase joins (adjacent RNA) nucleotides;
  • (By) phosphodiester bonds (between adjacent nucleotides);
  • Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mature mRNA);
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11
Q

Describe Translation [5]

A
  • (mRNA attaches) to ribosomes OR (mRNA attaches) to rough endoplasmic reticulum;
  • (tRNA) anticodons (bind to) complementary (mRNA) codons;
  • tRNA brings a specific amino acid;
  • Amino acids join by peptide bonds;
  • (Amino acids join together) with the use of ATP;
  • tRNA released (after amino acid joined to polypeptide);
  • The ribosome moves along the mRNA to form the polypeptide;
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12
Q

Describe the role of ATP in the process of translation in protein synthesis. [2]

A
  • Releases energy;
  • (So) peptide bonds form between amino acids OR (So) amino acid joins to tRNA;
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13
Q

A mutation in a gene coding for an enzyme
could lead to the production of a non-functional enzyme. Explain how [3]

A
  • Change in base sequence (of DNA/gene);
  • Change in amino acid sequence / primary structure (of enzyme);
  • Change in hydrogen/ionic/ disulphide bonds;
  • Change in the tertiary structure/active site (of enzyme);
  • Substrate not complementary/cannot bind (to enzyme / active site) / no enzyme-substrate complexes form;
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14
Q

Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why.

A
  • Triplets code for same amino acid
  • Occurs in introns /non-coding sequence;
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15
Q

Define ‘gene mutation’ and explain how a gene mutation can have:
* no effect on an individual
* a positive effect on an individual.

A
  • (Definition of gene mutation)
  • Change in the base/nucleotide (sequence of chromosomes/DNA);
  • Results in the formation of new allele;
  • (Has no effect because)
  • Genetic code is degenerate (so amino acid sequence may not change); OR
  • Mutation is in an intron (so amino acid sequence may not change);
  • Accept description of ‘degenerate’, eg some amino acids have more than one triplet/codon.
  • Does change amino acid but no effect on tertiary structure;
  • (New allele) is recessive so does not influence phenotype;
  • (Has positive effect because)
  • Results in change in polypeptide that positively changes the properties (of the protein) OR Results in change in polypeptide that positively changes a named protein; For ‘polypeptide’ accept ‘amino acid sequence’ or ‘protein’.
  • May result in increased reproductive success OR May result in increased survival (chances);
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16
Q

Name the type of gene mutation that has no effect on the Primary structure of a polypeptide.

A

Substitution / Silent

17
Q

Explain how natural selection produces changes within a species. [5]

A
  • Variation between members of population / species is caused by mutation;
  • Predation / disease / competition results in differential survival;
  • Some have adaptations that favour survival;
  • Differential reproductive success / survive to reproduce/ have more offspring;
  • Pass on their advantageous alleles;
  • Changes allelic frequencies
18
Q

Name 3 types of single point gene mutation.

A
  1. Addition
  2. Deletion
  3. Substitution
19
Q

Name 4 types of chromosomal mutation

A
  1. Duplication
  2. Inversion
  3. Translocation
  4. Non-disjunction
20
Q

When do most mutations occur?

A

DNA replication;
S phase of Interphase

21
Q

Which process may lead to:

  1. Inversion and Translocation mutations
  2. Non-disjunction mutations?
A
  1. Meiosis 1
  2. Meiosis 2
22
Q

State 3 factors that affect reproductive success or survival?

A
  1. Competition (Inter or Intraspecific)
  2. Predation
  3. Pathogens
23
Q

Name 4 selection pressures

A

Any 4 Biotic or Abiotic factors

24
Q

Why is a Log scale graph used?

A

There is a large range in ……….(y axis label)

25
Q

If the T value is 15 and the critical value is 3.4. What can you conclude?

Use the words probability and chance in your answer.

A

The probability that the difference is due to chance is less than 5%.
The difference is significant.
Reject the Null hypothesis.

26
Q

When would you use the Student’s T test?

A

Comparing the difference between TWO means