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biology year 1 > 3.4.2 DNA and protein synthesis > Flashcards

3.4.2 DNA and protein synthesis Flashcards

1
Q

Define genome

A

complete set of genes in the cell

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2
Q

Define proteome

A

The full range of proteins that a cell can make

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3
Q

Define codon

A

Three bases on mRNA that code for an amino acid

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4
Q

Define anti-codon

A

Three bases on tRNA that are complementary to the codon on mRNA

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5
Q

Name the process that removes base sequences from pre-mRNA to form mRNA.

A

Splicing

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6
Q

Give some ways in which the structure of an mRNA molecule is different from the structure of a tRNA molecule.

A
  • mRNA is a single helix where as tRNA is a clover shaped molecule
  • mRNA do not contain hydrogen bond where as tRNA do
  • mRNA do not have base pairing where as tRNA do
  • mRNA has codons where as tRNA has anti-codons
  • mRNA don’t have an amino acid binding site where as tRNA do
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7
Q

Explain the difference between pre-mRNA and mRNA.

A
  1. Pre-mRNA contains introns where as mRNA contains only exons;
  2. mRNA has undergone splicing, pre-mRNA has not.
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8
Q

What is the role of RNA polymerase during transcription?

A

To join RNA nucleotides together (by forming phosphodiester bonds) to form mRNA

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9
Q

Name the three steps involved in protein synthesis

A

Transcription
Splicing
Translation

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10
Q

Describe how mRNA is produced in the nucleus of a cell.

A
  1. DNA helicase breaks the hydrogen bonds holding complementary base pairs
  2. One DNA strand acts as a template
  3. Free RNA nucleotides are attracted to DNA template strand.
  4. RNA nucleotides bind to their complementary base pair on the template strand - A>U; C>G
  5. RNA polymerase joins RNA nucleotides together
  6. Pre-mRNA is spliced to remove the introns
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11
Q

Explain the role of the anticodon in protein synthesis.

A

Anticodons on the tRNA bind to codons on the mRNA
Anticodons are complementary to those on the codon
So the correct amino acid is brought to the ribosome

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12
Q

Name the organelle involved in translation.

A

Ribosomes

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13
Q

Describe the role of tRNA in the process of translation.

A
  1. Anticodons on tRNA are complementary to specific codons on mRNA
  2. A specific amino acid is bound to the tRNA
  3. This amino acid is carried to the ribosome
  4. Ribosome moves along mRNA.
  5. Peptide bond forms between adjacent amino acids.
  6. Via condensation reaction
  7. Requires ATP.
  8. Ribosome detaches from mRNA when STOP codon reached.
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14
Q

Starting with mRNA, describe how the process of translation leads to the production of a polypeptide.

A
  1. The mRNA attaches to a ribosome
  2. Anticodons on tRNA are complementary to specific 3. codons on mRNA
  3. A specific amino acid is bound to the tRNA
  4. This amino acid is carried to the ribosome
  5. Ribosome moves along mRNA.
  6. Peptide bond forms between adjacent amino acids.
  7. Via condensation reaction
  8. Requires ATP.
  9. Ribosome detaches from mRNA when STOP codon reached.
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15
Q

What is a histone?

A

A protein that DNA forms a complex with to allow it to be condensed into a chromosome.

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16
Q

When chromosomes become visible at the start of cell division, they appear as 2 threads joined at a central point called a…

A

centromere

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17
Q

The 2 condensed ‘threads’ of DNA that are joined at a centromere and make up a chromosome are called…

A

sister chromatids

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18
Q

Describe how DNA is packed into a chromosome.

A
  1. DNA molecule combines with histones.
  2. DNA-Histone complex begins to coil and fold to form loops.
  3. Loops coil further and pack together to form the chromosome.
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19
Q

What is meant by homologous chromosomes?

A
  1. A pair of corresponding maternal and paternal chromosomes.
  2. Their genes (are the same) are at the same loci so they determine the same characteristics.
20
Q

The total number of maternal AND paternal chromosomes in an organism is called its…

A

diploid number

21
Q

If a tRNA is involved what stage of protein synthesis are we looking at?

A

translation

22
Q

what shape does a tRNA have?

A

clover shape

23
Q

The codon on mRNA is AUG - what will be the complementary DNA and anti-codon?

A

DNA - TAC

anti-codon - UAC

24
Q

How do new alleles come about?

A
  1. Random mutations alter coding sequences.
  2. This leads to changes in the amino acid sequence.
  3. This leads to a different polypeptide with a possibly different function/non-functional.
25
Q

Do homologous chromosomes carry the same alleles (version of genes)?

A

No - they do carry same genes

26
Q

Define allele.

A

A version of a gene e.g. blue and brown versions of the eye colour gene.

27
Q

How do new alleles come about?

A
  1. Random mutations alter coding sequences.
  2. This leads to changes in the amino acid sequence.
  3. This leads to a different polypeptide with a possibly different function/non-functional.
28
Q

How are DNA nucleotides different to RNA nucleotides?

A

DNA has thymine RNA has uracil

DNA has deoxyribose RNA has ribose

29
Q

How is mRNA structure different to tRNA?

A

mRNA longer
mRNA straight - tRNA clover shape
mRNA has no paired bases/no hydrogen bonds

30
Q

Describe how mRNA is made in the nucleus

A
  1. Helicase;
  2. Breaks hydrogen bonds;
  3. Only one DNA strand acts as template;
  4. RNA nucleotides attracted to exposed bases;
  5. (Attraction) according to complemtary base pairing rule (AU, GC, TA, CG);
  6. RNA polymerase joins (RNA) nucleotides together;
  7. Pre-mRNA formed and is spliced to remove introns
  8. forming mRNA;
31
Q

name the 3 bases in mRNA that codes for a specific amino acid

A

codon

32
Q

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

A

mRNA binds to ribosome
two codon binding sites
tRNA with specific anticodon bind to codon
formation of a peptide bond in ribosome between amino acids
ribosome moves along mRNA

33
Q

The base sequence of mRNA maybe different the sequence of pre-mRNA in eukaryotic cells

A

introns in pre mRNA
splicing removes these introns
so only exons present in mRNA

34
Q

define degenerate

A

more than one codon codes for a single amino acid

35
Q

describe how mRNA differs to tRNA

A
  1. mRNA has no H bonds tRNA does
  2. mRNA has codon, tRNA has anticodon
  3. mRNA is longer
  4. mRNA linear, tRNA clover shaped
  5. mRNA has no AA binding site, tRNA does
36
Q

Describe translation

A
  1. mRNA binds to ribosome
  2. ribosomes moves to START codon (AUG)
  3. 2 codons fit in the ribosome
  4. first tRNA enters carrying specific AA
  5. anticodon binds to mRNA codon
  6. second tRNA enters - 2 tRNA binding sites
  7. AA join by peptide bond using ATP
  8. ribosome moves along to next codon to read
37
Q

messenger RNA (mRNA) is used during translation to form polypeptides. describe how mRNA is produced in the nucleus of a cell?

A
  • DNA helicase causes strands to separate
  • by breaking hydrogen bonds
  • free RNA nucleotides are attracted to exposed non-coding strands
  • complementary base pairing occurs
  • RNA polymerase binds RNA nucleotides together
  • splicing occurs to remove introns
38
Q

different sequences of bases codes for different proteins. explain how?

A
  • proteins are made of different amino acids

- these amino acids code for different triplets

39
Q

explain how copying bases more than once may give rise to a difference in the protein?

A
  • may change the base sequence via mutation

- will change the amino acid sequence

40
Q

at what stage in the cell cycle would these error in copying DNA bases occur?

A

interphase

41
Q

starting with mRNA in the nucleus of a cell, describe how a molecule of protein is synthesised?

A
  • mRNA leaves nucleus via nuclear pore
  • travels to ribosome
  • tRNA molecules bring amino acid molecules to ribosome
  • complementary base pairing occurs
  • peptide bonds form between amino acid molecules
  • tRNA detaches and brings another amino acid to ribosome
  • ribosome moves along mRNA
42
Q

dna is a polymer of nucleotides. each nucleotide contains an organic base.

explain how the organic bases help stabilise the structure of dna?

A
  • hydrogen bonds between base pairs hold 2 strands together

- many hydrogen bonds provides strength

43
Q

suggest one advantage of showing the genetic code as base sequences on mrna rather than triplets on dna?

A

dna has 2 strands each with diff complementary base sequence

44
Q

suggest the role of mrna triplets UAG, UGA, UAA?

A
  • stop translation

- results in detachment of polypeptide from ribosome

45
Q

in a eukaryotic cell transcription results in a molecule of pre-mrna that is modifief to produce mrna.

in a prokaryotic cell transcription produces mrna directly.

explain this difference?

A
  • dna of eukaryotic cells has non-coding regions

- these regions removed from pre-mrna

biology year 1 (45 decks)

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