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AS Level Biology 3.4 > 3.4.1 DNA, genes and chromosomes > Flashcards

3.4.1 DNA, genes and chromosomes Flashcards

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1
Q

What is a DNA triplet?

A

A sequence of three bases in a gene.

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2
Q

What is an intron?

A

A section of a gene that doesn’t code for amino acids.

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3
Q

What are non-coding repeats?

A

A region of multiple repeats, outside of genes, that don’t code for amino acids.

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4
Q

What is a locus?

A

A locus refers to the same fixed positions between chromosomes in a homologous pair.

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5
Q

What is a gene?

A

A sequence of DNA bases that codes for either a polypeptide or functional RNA.

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6
Q

What determines the order of amino acids in a particular polypeptide?

A

The order of bases in a gene.

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7
Q

Describe how DNA is stored in eukaryotic cells.

[5 marks]

A

Any five points from:

  • In the nucleus of eukaryotic cells, DNA is stored as chromosomes.
  • It is linear.
  • It is wound around proteins called histones.
  • Mitochondria and chloroplasts in eukaryotic cells also contain DNA.
  • In mitochondria and chloroplasts, the DNA is short and circular.
  • The DNA in mitochondria/chloroplasts is not associated with histones.
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8
Q

A scientist is studying a DNA sequence that is made up of 3800 nucleotide pairs. Exons account for 672 of the nucleotide pairs. Introns account for 3128 of the nucleotide pairs. The sequence codes for a section of a polypeptide. How many amino acids will make up this section of the polypeptide?
[2 marks]

A

672 ÷ 3 = 224 amino acids

Only the exons code for amino acids.

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9
Q

Describe how DNA is stored in prokaryotic cells.

A
  • Prokaryotes carry DNA as chromosomes…
  • …but the DNA molecules are shorter and circular.
  • DNA isn’t wound around histones.
  • It condenses to fit in the cell by supercoiling.
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10
Q

What is a cell’s ‘genome’?

A

The complete set of genes in the cell.

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11
Q

What is a cell’s ‘proteome’?

A

The full range of proteins that the cell is able to produce.

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12
Q

What is the genetic code?

A

The sequence of base triplets (codons) in mRNA which code for specific amino acids.

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13
Q

Why is the genetic code described as degenerate?

A
  • There are more possible combinations of triplets than there are amino acids.
  • Some amino acids are coded by more than one base triplet.
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14
Q

Why is the genetic code described as universal?

A

The same specific base triplets code for the same amino acids in all living things.

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15
Q

Why is the genetic code described as non-overlapping?

A
  • Each base triplet is read in sequence, separate from the triplet before it and after it.
  • Base triplets don’t share their bases.
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AS Level Biology 3.4 (7 decks)

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