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Biology > Protein Synthesis and Selection A1 > Flashcards

Protein Synthesis and Selection A1 Flashcards

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1
Q

Name the components of a nucleotide.

A
  1. phosphate group
  2. deoxyribose sugar
  3. organic base (A,T,C,G,U)
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2
Q

Name the bonds between bases in DNA.

A

hydrogen bonds

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3
Q

What’s a haploid?

A

one copy of each chromosome

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4
Q

What is a diploid?

A

two copies of each chromosome

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5
Q

What is a centromere?

A
  1. holds the chromatids together
  2. attaches chromatids to spindles
  3. allows chromatids to be separated
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6
Q

What is a histone?

A

Proteins which DNA is wrapped around.

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7
Q

Meiosis results in cells that have the haploid number of chromosomes and show genetic variation.
Show how.
(6)

A
  1. homologous chromosomes pair up
  2. crossing over, chiasmata form
  3. chromosomes separate at random
  4. produces varying combinations of chromosomes/genes
  5. chromatids separate at meiosis (ii) later
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8
Q

How does crossing over occur?

A
  1. chromosomes in each homologous pair twist around each other
  2. chromosomes break and re-join to the chromatid on the sister chromosome.
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9
Q

Describe the process of crossing over and how does it lead to genetic variation?
(4)

A
  1. chromosomes associate with each other
  2. chiasmata forms
  3. segments of DNA/alleles swap
  4. via independent assortment
  5. forming new combinations of chromosomes
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10
Q

Difference between stabilising and directional selection (graphs).

A
  1. stabilising tends to eliminate extremes and mode stay the same
  2. directional selection gains a new mode as the organisms predominant characteristics have changed
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11
Q

Define the term genetic variation.

A

Genetic variation is the presence of differences in sequences of genes between individual organisms of different species.

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12
Q

Describe the structure of proteins.
(7)

A
  1. polymer of amino acid
  2. joined by peptide bonds
  3. formed by condensation reactions
  4. primary structure is order of amino acids
  5. secondary structure is folding of polypeptide chains into alpha helix and beta pleated sheets due to hydrogen bonding
  6. tertiary structure is 3D folding due to hydrogen/ionic and disulphide bonds/bridges
  7. quaternary structure is 2 or more polypeptide chains
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13
Q

What happens to introns in splicing?

A

They get deleted so if mutation occurs in intron sector, it will have no effect on amino acid sequence as not translated due to being non-coding DNA.

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14
Q

What is a degenerate code?

A

Can have several different codons that code for the same amino acid eg CGA and CGC may both code.

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15
Q

Describe what happens during transcription.
(7)

A
  1. DNA helicase
  2. breaks hydrogen bonds so strands separate
  3. only one DNA strand acts as a template
  4. RNA nucleotides attracted to exposed bases
  5. attraction according to base pairing rule
  6. RNA polymerase joins RNA nucleotides together
  7. Pre-mRNA spliced to removed introns
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16
Q

Describe how proteins are digested in the human gut.
(4)

A
  1. hydrolysis of peptide bonds
  2. endopeptidases break polypeptide into smaller peptide chains
  3. exopeptidases remove terminal amino acids
  4. peptidases hydrolase/break down dipeptides into amino acids
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17
Q

Compare and contrast DNA and RNA.
(6)

A
  1. DNA is double stranded , RNA is single stranded
  2. DNA is long, RNA is short
  3. Thymine is DNA, replaced with uracil in RNA
  4. deoxyribose in DNA, ribose in RNA
  5. DNA has hydrogen bonds, mRNA doesn’t have hydrogen bonds
  6. DNA has introns, mRNA doesn’t have introns
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18
Q

What’s the role of RNA polymerase in transcription?

A

It joins the RNA nucleotides back together forming phosphodiester bonds.

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19
Q

Describe what happens during translation.
(6)

A
  1. mRNA translated translated at/moves to ribosome
  2. codon on mRNA
  3. tRNA brings amino acids to ribosomes
  4. codon binds with complementary anticodon on tRNA
  5. each tRNA specific to one amino acid
  6. formation of peptide bonds
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20
Q

Describe the appearance of a chromosome.

A
  1. chromosome is formed by two sister chromatids
  2. as DNA replication has occurred
  3. sister chromatids are being help together by centromere
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21
Q

Compare the structure of mRNA and tRNA.

A
  1. mRNA has hundreds of nucleotides in chain, tRNA has roughly 75
  2. mRNA has no hydrogen bonds, tRNA does
  3. mRNA is single stranded and straight, tRNA has a cloverleaf shape
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22
Q

A mutation in a gene coding for an enzyme could lead to the production of a non-functional enzyme.
Explain how.
(6)

A
  1. change in base sequence of DNA/gene
  2. change in amino acid sequence/primary structure of enzyme
  3. change in hydrogen/ionic/disulphide bonds
  4. change in the tertiary structure/active site of enzyme
  5. substrate not complementary / cannot bind to enzyme/active site
  6. no enzyme-substrate complexes formed
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23
Q

Name the bases, and state which are purines and pyrimidines.
(4)

A
  1. Adenine (purine) (A+T) pair together to form 2 hydrogen bonds.
  2. Thymine (pyrimidine)
  3. Guanine (purine) (G+C) pair together to form 3 hydrogen bonds.
  4. Cytosine (pyrimidine)
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24
Q

Explain how crossing over increases genetic diversity.

A
  1. chromosomes associate with each other
  2. chiasmata forms
  3. segments of DNA/alleles swap
  4. forming new combinations of chromosomes
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25
Q

How does meiosis cause genetic variation?

A
  1. random fertilisation of haploid gametes can produce variation in population
  2. mutations can occur causing genetic variation
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26
Q

Describe what happens to chromosomes in meiosis.
(6)

A
  1. chromosomes pair up
  2. chromosomes associate in homologous and formation of bivalents, crossing over chiasmata formed
  3. joining to spindle fibres at equator
  4. these join via the centromere
  5. homologous chromosomes move to opposite poles and chromosomes separate
  6. pairs of chromatids separate in 2nd division
27
Q

State and explain Chargaff’s rule.

A

DNA from any species of any organism should have a 1:1 stoichiometric ratio of purine to pyrimidine bases

28
Q

What’s an intron?

A

Part of a gene which does not code for a protein and is removed.

29
Q

What is insertion/addition?

A

When a base pair gets added to the base sequence, changing order of the sequence.

30
Q

Name the organelle involved in translation.

A

ribosome

31
Q

What is an anticodon?

A

3 nucleotides on tRNA that are complementary to codon on mRNA.

32
Q

What’s a mutation?

A

A change in the DNA base sequence.

33
Q

What’s a genome?

A

all the genetic material of an organism

34
Q

Describe how a deletion alters the structure of a gene.
(3)

A
  1. deletion causes 1 base to be removed from base sequence
  2. all other bases move along one in the sequence
  3. so wrong amino acid coded for if not degenerated
35
Q

Give two factors that increases the rate of gene mutations.

A
  1. ionising radiation
  2. length of time and exposure to mutagens or dosage
36
Q

What is a mutagenic agent?

A

a chemical which induces DNA mutations eg. UV light

37
Q

mRNA can be converted into cDNA. Name the enzyme used in this process.

A

Reverse transcriptase.

38
Q

What is selection pressure?

A

Selection pressure determines the spread of an allele within the gene pool.

39
Q

Define the term natural selection.

A

Process by which organisms that are better adapted to their environment survive and reproduce in greater numbers, resulting in the increase of the frequency of the advantageous allele within the population.

40
Q

What is substitution?

A

When one base pair gets replaced with another, changing order of sequence.

41
Q

Why is genetic code described as being universal?

A

Same triplet codes for same amino acid.

42
Q

What is a carcinogen?

A

Causes cancer eg. radiation

43
Q

Explain how selection occurs in living organisms.
(6)

A
  1. variation due to mutations
  2. different environmental/biotic conditions
  3. selection for different advantageous features/characteristics/mutations/alleles
  4. differential reproductive success (selected organisms survive and reproduce)
  5. leads to change in allele frequency
  6. occurs over a long time period
44
Q

Starting with mRNA in the nucleus of a cell describe how a molecule of protein is synthesised.
(6)

A
  1. mRNA leaves via nucleus pore, to ribosomes
  2. tRNA molecules bring amino acids to ribosome
  3. specific to tRNA molecule for specific amino acid
  4. anticodon of tRNA corresponds/complementary to codon on mRNA
  5. peptide bonds form between amino acids, tRNA detaches and collects another amino acid
  6. ribosome moves along mRNA
45
Q

What’s an allele?

A

A different version of the gene.

46
Q

Define translation briefly.

A

mRNA is ‘read’ and amino acids are sequenced to form proteins.

47
Q

What is codon?

A

3 nucleotides on mRNA which correspond to a specific amino acid

48
Q

What’s a loci?

A

the location/position of a gene on a chromosome

49
Q

Define meiosis.

A

Cell division which results in sex cells.

50
Q

What is a proteome?

A

the entire set of protein which can be expressed.

51
Q

Eukaryote definition?

A

organisms with DNA in nucleus

52
Q

What is DNA and what’s it made up of?

A

a polymer made up of many nucleotides (monomer units) joined together by a condensation reaction, called polynucleotide chains.

53
Q

Define mitosis.

A

cell division which results in identical daughter cells

54
Q

What is a sister chromatid?

A

‘one half’ of the duplicated chromosome

55
Q

Define transcription briefly.

A

a gene is copied to mRNA

56
Q

What is splicing?

A

the removal of introns from mRNA before proteins are made

57
Q

What’s an exon?

A

part of a gene which codes for a protein

58
Q

Describe the part played by RNA in protein synthesis.

A
  1. carries coded info about the sequence of amino acids
  2. copied from DNA/gene, code is in triplets
  3. form amino acids
59
Q

Explain how the structure of DNA is related to its function.
(6)

A
  1. sugar-phosphate backbone provides strength and stability
  2. double-stranded for semi-conservative replication
  3. large molecule so lots of information can be stored
  4. double helix stabilises molecule (so code not affected)
  5. chains held together by weak hydrogen bonds so they can split for transcription
  6. coiled to give compact shape
60
Q

What are homologous chromosomes?

A

Homologous chromosomes carry the same genes but are not genes but are not genetically identical as they carry different alleles.

61
Q

What is a non-overlapping codon?

A

A base from one triplet cannot be used in an adjacent triplet.

62
Q

Explain the difference between pre-mRNA and mRNA.

A

pre m-RNA contains introns/mRNA contains only exons

63
Q

The number of different alleles of genes in a population.

A

genetic diversity (gene pool)

Biology (27 decks)

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