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AQA Biology A level > DNA, Genes and Protein Synthesis > Flashcards

DNA, Genes and Protein Synthesis Flashcards

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1
Q

What is a gene?

A

Section of DNA that contains the coded information for amino acid sequence for the making of polypeptides and functional RNA (rRNA and tRNA)

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2
Q

What are the 3 features of the genetic code?

A

Degenerate - each amino acid is coded for by more than one triplet
Universal - same sequence of bases that codes for the same amino acids
Non-overlapping - each base is only part of 1 triplet of bases that codes for 1 amino acid

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3
Q

How many amino acids that occur in proteins?

A

20

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4
Q

How many codes do:
-a pair of bases
-3 bases
produce?

A

Pair- 4 squared = 16

3- 4 cubed = 64

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5
Q

What are Exons?

A

Sequences that code for amino acids

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6
Q

What are Introns?

A

Separate exons and are non-coding sequences

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7
Q

What are the differences between DNA in a prokaryote and a eukaryote?

A 
Prokaryotes:
Shorter
Circular 
Not associated with protein molecules 
Do not have chromosomes

Eukaryotes:
Longer
Linear
Associated with proteins called histones to form chromosomes
Mitochondria and chloroplasts contain DNA which is similar to prokaryotic DNA -> links to endosymbiotic theory

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8
Q

What is the structure of a chromosome?

A

2 chromatids held together by centromere

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9
Q

What are homologous chromosomes?

A

Two chromosomes that carry the same genes but not always the same alleles

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10
Q

What is an allele?

A

The number of alternative forms of a gene

Each person inherits one allele from each parent

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11
Q

What is a mutation?

A

Any change in the base sequence of a gene produces a new allele of the gene, resulting in new amino acids and as a result a different polypeptide, therefore a different protein

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12
Q

What is a codon?

A

Sequence of three bases on mRNA that codes for a single amino acid

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13
Q

What is a genome?

A

Complete set of genes in a cell

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14
Q

What is a proteome?

A

Full range of proteins produced by the genome

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15
Q

What are the two types of RNA important for proteins synthesis?

A

Messenger RNA

Transfer RNA

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16
Q

What is the structure of messenger RNA? + function

A
  • Leaves through the nuclear pores
  • Long straight chain of nucleotides
  • Carries specific info of a protein
  • Globular
17
Q

What is the structure of transfer RNA? + function

A
  • Clover leaf shape with amino acid and binding site
  • Each tRNA is specific for one amino acid
  • Has a sequence of 3 bases called an anti-codon which are complimentary to codons of mRNA molecule
18
Q

What does a gene occupy?

A

A gene occupies a fixed position, called a locus, on a particular DNA molecule.

19
Q

What is a start codon?

A

Indicates the start of gene

20
Q

What is a stop codon?

A

End of sequence when 3 bases do not code for amino acid

21
Q

What is the order of steps in protein synthesis?

A 
DNA 
mRNA
tRNA
amino acid 
Polypeptide
Protein
22
Q

How does DNA make proteins?

A
  • DNA provides instructions in form of bases
  • Transcription, complimentary section of part of this base sequence is made in form of pre-mRNA
  • pre-mRNA is spliced to form mRNA
  • Translation, mRNA is used as a template to which complimentary tRNA molecules attach and amino acids that they carry are linked to form a polypeptide
23
Q

What is transcription?

A

Transcription is the process of making pre-mRNA using part of DNA as a template

  1. DNA strands separate by RNA helicase
  2. Free nucleotides bind to one strand by specific base pairing
  3. U to A, C to G
  4. RNA polymerase joins nucleotides to form mRNA
24
Q

What is the splicing or pre-mRNA?

A

in prokaryotes- transcription results in the production of mRNA from DNA

in eukaryotes- transcription results in the production of pre-mRNA, which is spliced to form mRNA

Splicing is the process of removing introns and joining exons

25
Q

What is the structure of ribosomes?

A
  • Large and small sub-units, mRNA passes through the middle
  • 40% rRNA nd 60% proteins
  • two sites for RNA attachment
26
Q

What is translation?

A

Process of decoding mRNA into a polypeptide chain

  1. mRNA moves to ribosome
  2. Codon binds with complimentary anticodon on tRNA
  3. Each tRNA specific to one amino acid
  4. Peptide bonds form and join amino acids

AQA Biology A level (13 decks)

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