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Biology AS > DNA, Genes and Chromosomes > Flashcards

DNA, Genes and Chromosomes Flashcards

1
Q

Gene

A

a base sequence of DNA that codes for the amino acid sequence of a polypeptide or a functional RNA and is located at a particular locus on a DNA molecule.
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2
Q

Locus

A

the fixed position on a particular DNA molecule occupied by a particuar gene

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3
Q

Allele

A

a different verison of the same gene

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4
Q

features of eukaryotic DNA

+ what are chromosomes formed of?

A
  • DNA molecules are long and linear
  • associated with proteins called histones
  • DNA molecules and histones form a chromosome
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5
Q

Features of prokaryotic DNA

A

short, circular, not associated with protein

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6
Q

3 features of the genetic code

A

universal, non-overlapping and degenerate

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7
Q

How is the genetic code degenerate?

A

some amino acids are coded for by more than 1 base triplet - because there are 20 amino acids and 64 triplets.

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8
Q

How is the genetic code non-overlapping?

A

each base in the genetic code is only read once, part of 1 triplet which is separate from adjacent triplets.

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9
Q

How is the genetic code universal?

A

the same base triplets code for the same amino acids in all living organisms. This is evidence for evolution.

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10
Q

DNA in mitochondria and chloroplasts - structure

A

short, circular and not associated with protein, like the DNA of prokaryotes

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11
Q

Where in a eukaryotic cell is DNA found?

A

nucleus, mitochondria, chloroplasts

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12
Q

Genome

A

the complete set of genes in a cell

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13
Q

Proteome

A

the full range of proteins a cell is able to produce

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14
Q

mRNA structure

A

single polynucleotide strand/ helix

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15
Q

tRNA structure

A
  • single polynucleotide strand folded into a clover shape - this structure is held into place by hydrogen bonds between complementary base pairs.
  • A specific sequence of bases at one end forms the anticodon, which pairs with the complementary mRNA codon during translation.
  • There is an amino acid binding site at the other end.
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16
Q

role of mRNA

A

carries genetic information from DNA to the ribosomes

17
Q

role of tRNA

A

carries amino acids to ribosomes in specific sequnce (as coded for by mRNA)

18
Q

what can a gene code for?

A
  • the amino acid sequence of a polypeptide

* a functional RNA (including ribosomal RNA and tRNAs)

19
Q

What is a triplet and what does it code for?

A

a sequence of 3 DNA bases, codes fr a specific amino acid.

20
Q

What does the DNA base sequence of a gene determine?

A

the sequnce of amino acids during protein synthesis/ prmary protein structure.

21
Q

What does most nuclear DNA code for?

A

not polypeptides - e.g. non-coding multiple repeats between genes.
introns

22
Q

what do exons code for?

A

amino acid sequences

23
Q

what are introns?

A

non-protein coding sequences which separate exons within genes

24
Q

what does transcription produce in eukaryotes? prokaryotes?

A

pre-mRNA - introns are also transcribed

mRNA - as no introns are present

25
Q

Describe the process of transcription

A

1) DNA helicase breaks the hydrogen bonds between complementary base pairs, so the 2 strands of DNA separate and unwind.
2) only 1 of the 2 DNA strands acts as a template.
3) complementary free RNA nucleotides are attracted to the exposed bases on the template strand according to the base pairing rule - C to G, A to U
4) RNA pllymerase joins the RNA nucleotides together in a series of condensation reactions

26
Q

How is mRNA formed from pre-mRNA in eukaryotes?

A

by splicing

27
Q

What is translation?

A

production of polypeptides from the mRNA codon sequence

28
Q

What is transcription?

A

production of mRNA from DNA

29
Q

Process of translation

A

1) mRNA attaches to ribosome
2) tRNA with anticodon complementary to 1st mRNA codon binds to mRNA by complenentary base pairing
3) tRNA brings a specific amino acid - attachment requires ATP.
4) 2 amino acids are joined by a peptide bond - in a condensation reaction which requires ATP.
5) ribosome moves along mRNA, so polypeptide chain builds up.
6) when the stop codon on mRNA is reached, the ribosome detaches from mRNA and the polypeptide chain is complete.

Biology AS (10 decks)

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