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A Level Biology > DNA, RNA and Protein Synthesis > Flashcards

DNA, RNA and Protein Synthesis Flashcards

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1
Q

Difference between mRNA and tRNA

A

mRNA has codons and tRNA has anticodons.

mRNA doesn’t contain hydrogen bonds. tRNA does.

mRNA is bigger than tRNA.

mRNA is a single helix. tRNA is clover shaped.

mRNA has no binding site for Amino Acids.

mRNA has no base pairing. tRNA does.

mRNA made during transcription. tRNA involved in translation.

mRNA carried genetic code from DNA to the ribosomes where it’s used to make a protein during translation. tRNA carried amino acids that are used to make proteins to the ribosomes.

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2
Q

Similarities in mRNA and tRNA

A

Both single stranded. Yeah

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3
Q

Contrast the structures of DNA and mRNA molecules to give three differences

A
  1. Pentose sugar in DNA is deoxyribose.
    In mRNA it’s ribose.
  2. DNA double stranded
    mRNA single stranded.
  3. DNA - ATGC
    mRNA - AUGC
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4
Q

Proteome

A

Full range of proteins that the cell is able to produce.

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5
Q

Genome

A

Complete set of genes in the cell. The DNA that codes for these proteins

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6
Q

Codon

A

Sequence of three bases in mRNA that codes for Amino acids

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7
Q

Anticodon

A

Sequence of three bases on tRNA that joins by complementary pairing to the codon on mRNA.

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8
Q

Introns

A

Sections of RNA that are spliced out of Pre mRNA before mRNA is made. It’s none coding. (Sections of DNA that don’t code for AA)

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9
Q

Exons

A

Function sequence that codes for proteins

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10
Q

Universal

A

Same specific base triplets codes for the same Amino acid in all living things.

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11
Q

Non- overlapping

A

Each base is part of only one codon / triplet.

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12
Q

What’s the role of ATP in protein synthesis

A

Form a peptide bond.

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13
Q

Two results of the mutation substitution

A

Changed one DNA triplet.

Changes the primary/ tertiary structure as proteins been altered.

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14
Q

Results of mutation deletion

A

Gives a non- functional protein as all the triplets are altered from the point of mutation causing a frame shift.

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15
Q

what does it mean when a DNA code is said to degenerate

A

More codons/ triplets than Amino acids.

Some Amino acids have more than one triplet.

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16
Q

Mutagenic agent

A

Increases rate of mutation

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17
Q

What are homologous chromosomes

A

Similar in size and shape

Have the same gene

Loci but not necessarily the same alleles.

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18
Q

What is crossing over and how does it regular in genetic variation

A

Chromatids of homologous chromosomes cross over.

Exchange pieces of DNA.

Gives new combinations of alleles.

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19
Q

Explain how independent segregation results in genetic variation

A

Pairs of homologous chromosomes separate and move to opposite poles of cells. It creates new allele combinations

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20
Q

What is non disjunction

A

When two chromatids of a pair enter the same daughter cell/ chromatids do not separate. results in a daughter cell with an extra chromosome.

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21
Q

How does random fertilisation increase genetic variation within a species

A

Crossing over and independent segregation means that every gamete is genetically different making every offspring of a specific pair unique.

It’s random which male gamete or female gamete fertilises.

22
Q

Give two differences between mitosis and meiosis

A

Meiosis homologous chromosomes pair.
Mitosis they behave independently.

Meiosis produces four daughter cells
Mitosis produces 2

Meiosis produces haploid daughter cells
Mitosis the diploid are the same as parent cell.

Meiosis produces genetically different daughter cells.
Mitosis produces identical daughter cells.

Meiosis has 2 divisions
Mitosis have one division.

23
Q

How do Eukaryotic and prokaryotes store DNA in different ways

A

Eukaryotic DNA molecules are longer forming a line being linear - has to wind up to fit in Nuc.
Prokaryotic are shorter and circular

Eukaryotes have chromosomes found in nucleus.
Prokaryotes have DNA carried as chromosomes.

Eukaryotes DNA wound around proteins called histones. They help support DNA. DNA coiled up very
Prokaryotes DNA isn’t wound around histones. It condenses to fit in the cell by super coiling.

In eukaryotes the mitochondria and chloroplasts contain DNA Short circular and not associated with proteins histones.

24
Q

Chromosomes

A

Only visible when dividing

Pairs of 23. 46 in total

DNA held together by histones.

Each thread called chromatid.

Replicated chromosomes.

Held together by centromeres.

Genes bound long length of chromosome.

Gametes contain half the chromosome (haploid).

Contain different versions of the same gene (allele).

Only an X shape when replicating.

25
Q

How is DNA packed into a chromosome

A

DNA combined with DNA histones.

DNA histones complex coiled and forms loops.

The loops coil and pack together even more to form chromosomes

26
Q

What is a gene

A

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

27
Q

What determines the order for Amino acids

A

The order of bases

28
Q

What is each amino acid codes for

A

Sequence of three bases in a gene

29
Q

What is a triplet

A

Sequence of three bases in a gene that codes for ones Amino acid

30
Q

Where is a gene found

A

Located at particular site on the DNA molecule called locus

31
Q

Genes that don’t code for polypeptide code for what

A

The functional RNA

32
Q

What is functional rna

A

RNA molecules other than mRNA which perform special tasks during proteins synthesis

33
Q

Describe the role of ribosomes in the production of a polypeptide

A
  1. The mRNA attaches itself to a ribosome.
  2. Two codons/ binding sites.
  3. Allows tRNA with anticodons to bind.
  4. Catalyses the formation of peptide bonds between Amino acids.
  5. Moves along (mRNA to next codon) / translocation
34
Q

What do most DNA in eukaryotic cells code for

A

Functional RNA

35
Q

Introns

A

Sections of RNA that are spliced out of pre-mRNA before mRNA Is made. It’s non coding sequence.

36
Q

Exons

A

Function sequence that codes for proteins/ Amino acids. The name for the genes that code.

37
Q

Introns are removed when

A

During protein synthesis

38
Q

What don’t prokaryotic DNA have

A

Introns

39
Q

Non coding repeats

A

Non-coding multiple repeats of base sequences between genes. They don’t code for Amino acids

40
Q

Locus

A

The fixed position of a gene on a chromosome

41
Q

What is the first stage of protein synthesis

A

Transcription

42
Q

Explain how mRNA is produced in the nucleus of a cell// explain first stage of protein synthesis

A
  1. DNA helicase breaks the hydrogen bonds separating strands and uncoiling them exposing complementary based pairs.
  2. One DNA strand acts as a template.
  3. free RNA nucleotides along exposed bases on template. The free RNA nucleotides are attracted to DNA template strand.
  4. RNA nucleotides bind to their complementary base pair on the template strand.
  5. RNA polymerase joins RNA nucleotides together. Hydrogen bonds reform and strands coil back into double helix.
  6. Pre-mRNA is spliced to remove the introns.
  7. stop signal makes mRNA detach from DNA.
43
Q

If no RNA polymerase binded what does that mean

A

No transcription can happen and so no mRNA made. Translation then doesn’t happen as no mRNA so protein synthesis is inhibited.

44
Q

What is the second stage of protein synthesis

A

translation

45
Q

What is translation

A

Occurs at ribosomes in cytoplasm in both eukaryotes and prokaryotes.

Amino acids get joined together to make a polypeptide chain, following the sequence of codons.

46
Q

Explain steps of translation

A
  1. mRNA attaches to ribosomes and tRNA molecules carry Amino acids to it.
    ATP provides energy so bond forms between AA and tRNA.
  2. tRNA molecule with an anticodon that’s complementary to the first codon on mRNA attaches to mRNA by specific base pairing.
  3. A second tRNA molecule attaches to the next codon on mRNA in the same way.
  4. The two Amino acids attached to tRNA are joined by a peptide bond. The first tRNA moves away leaving aa behind.
  5. The third tRNA molecule binds to next codon on mRNA. It’s Aa binds to first two and the second tRNA molecule moves away.
  6. Process continues until stop signal on mRNA molecule.
  7. Polypeptide chain moves away from ribosomes and translation is complete
47
Q

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

A
  1. mRNA attaches to a ribosome.
  2. Anticodons on tRNA are complementary to specific codons on mRNA.
  3. A specific AA is bound to the tRNA.
  4. That Amino acid is carried to the ribosome.
  5. Ribosome moves along mRNA
  6. Peptide bonds form between adjacent Amino acids.
  7. By a condensation reaction.
  8. Requires ATP
  9. When stop codon reached ribosomes detached from mRNA.
  10. Polypeptide chain moves away from ribosome and translation is complete.
48
Q

What are the three adaptations/features of a genetic code

A

Non-overlapping - each base part of only one codon/ triplet.

degenerate - more triplets/ codons than Amino acids.

universal - same specific base triplets code for the same Amino acids in all living organisms.

49
Q

What is genetic code

A

The sequence of bass triplets (codons) in mRNA which code for specific Amino acids.

50
Q

Explain why the percentages of bases from the middle part of the chromosome and the end part are different

A

Due to them having different base sequences transcribed from different DNA

51
Q

Explain the difference in the number of nucleotides. Exam questions

A

Introns

A Level Biology (9 decks)

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