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Biology > TOPIC 4 MARK SCHEME SHIT > Flashcards

TOPIC 4 MARK SCHEME SHIT Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Suggest how the change in the anticodon of a tRNA leads to mitochondrial disease (3)

A
  1. Change to tRNA leads to wrong amino acid being incorporated into protein
  2. Tertiary structure changed
  3. Protein required for oxidative phosphorylation/Krebs cycle, so less/no ATP made
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2
Q

Describe how a gene is a code for the production of a polypeptide. DO NOT INCLUDE INFO ABOUT TRANSCRIPTION OR TRANSLATION (3)

A
  1. Base/nucleotide sequence
  2. (In) triplet(s)
  3. (Determines) order/sequence of amino acids/primary structure (in polypeptide)
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3
Q

Define an exon (1)

A

Base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids/primary structure

NOTICE HOW “PROTEIN” ISN’T ALLOWED

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4
Q

Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome (2)

A
  1. DNA that doesn’t code for protein/polypeptides/(sequences of) amino acids/tRNA/rRNA
  2. (Positioned) between genes
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5
Q

Give 2 reasons why not all mutations in the nucleotide sequence of a gene causes a change in the structure of a polypeptide (2)

A
  1. Triplets code for same amino acid
    Accept: DNA/code/triplets are degenerate
  2. Occurs in introns/non-coding sequence
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6
Q

Suggest how a mutation can lead to the production of a protein with one missing amino acid (2)

A

Loss of codon/3 bases/triplet

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7
Q

Describe how mRNA is produced in the nucleus of a cell

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 complementary base pair rule
  6. RNA polymerase joins (RNA) nucleotides together via phosphodiester bonds
  7. Pre-mRNA spliced to remove introns
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8
Q

Describe how a polypeptide is formed by translation of mRNA

A
  1. (mRNA attaches to) ribosomes/rough endoplasmic reticulum
  2. ribosome moves to start codon
  3. (tRNA) anticodons (bind to) complementary (mRNA) codons
  4. tRNA brings a specific amino acid
  5. Amino acids join by peptide bonds
  6. (Amino acids join together) using ATP
  7. tRNA released (after amino acid joined to polypeptide)
  8. The ribosome moves along the mRNA to form the polypeptide
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9
Q

Suggest why the scientist took his sample from the population at random (1)

A
  1. Avoids bias
  2. Results (likely to be) reliable/repeatable
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10
Q

Describe how to make a 1 in 10 dilution and then use this to make a 1 in 1000 dilution of the original liquid culture of bacteria (3)

A
  1. Add 1 part culture to 9 parts liquid
  2. Mix
  3. Repeat using 9 parts fresh liquid and 1 part of 10^-1 and 10^-2 dilutions to make 10^-3 dilution
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11
Q

Suggest why student decided not to use 1 in 10 dilution for determining the number of cells in the undiluted liquid culture (2)

A
  1. COUNT unlikely to be accurate/reproducible/repeatable/reliable
  2. Because too many cells/cells overlapping/not spread out
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12
Q

Suggest & explain one reason why bacteria resistant to A are more common than bacteria resistant to B in farm animals (2)

A
  1. A used more often/in higher doses
  2. Resistant bacteria more likely to pass on allele/gene for resistance
  3. More/higher frequency of mutations
  4. Gene passed on to more bacteria
  5. A used over longer time period
  6. More time for (chance) mutation to occur/for selection to occur
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13
Q

Explain what is meant by a hierarchy (2)

A
  1. Groups within groups
  2. No overlap
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14
Q

Explain what is meant by a phylogenetic group (1)

A

(Grouped according to) evolutionary links/history/relationships/common ancestry

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15
Q

Explain why having fewer differences in amino acid sequences compared with humans shows that it’s the most closely related to humans (2)

A
  1. Similar primary structure
  2. So similar DNA sequence/base sequence
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16
Q

Explain why diversity of insects in the area decreased after the forest was cleared (3)

A
  1. Fewer niches
  2. Fewer food sources
  3. Fewer plant species
17
Q

Explain the role of independent segregation in meiosis (2)

A
  1. Genetic variation
  2. Different combinations of maternal and paternal chromosomes/alleles
18
Q

Suggest why an animal crossed from a zebra (32 chromosomes) and a donkey (62 chromosomes) is infertile (2)

A
  1. 47/odd/uneven number of chromosomes
  2. Chromosomes cannot pair/are not homologous/chromosome number can’t be halved/meiosis can’t occur/sex cells/haploid cells aren’t produced
19
Q

Define genetic diversity (1)

A

Number of different alleles OF EACH GENE

20
Q

Give 3 ways in which courtship behaviour increases probability of successful mating (3)

A
  1. Recognise/identify/attract same species
  2. Stimulates/synchronises mating/production/release of gametes
  3. Recognition/attraction of mate/opposite sex
  4. Indication of maturity/fertility/readiness to mate
  5. Formation of a pair bond
21
Q

Describe 2 differences between the structure of a tRNA molecule and the structure of a mRNA molecule (2)

A
  1. tRNA is clover-leaf shaped, mRNA is linear
  2. tRNA has H bonds, mRNA doesn’t
  3. tRNA has an amino acid binding site, mRNA doesn’t
  4. tRNA has anticodon, mRNA has codon
22
Q

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation (3)

A
  1. tRNA bring specific amino acid (to ribosome)
  2. anticodon (on tRNA) binds to codon (on mRNA)
  3. amino acids join by condensation reaction/join to form a peptide bond (using ATP)
23
Q

Describe the role of a ribosome in the production of a polypeptide. DO NOT INCLUDE TRANSCRIPTION (3)

A
  1. mRNA binds to ribosome
  2. idea of TWO codons/binding sites
  3. (allows) tRNA with ANTICODONS to bind/associate
  4. (catalyses) formation of peptide bond between amino acids
  5. moves along (mRNA to the next codon)
24
Q

EXPLAIN one other way genetic variation within a species is increased apart from mutation (2)

A
  1. Random fertilisation
  2. Produces new allele combinations
25
Q

Define ‘gene mutation’ and explain how a gene mutation can have
• no effect on an individual
• a positive effect on an individual (4)

A
  1. Change in the base/nucleotide (sequence of DNA)
  2. Results in the formation of a new ALLELE
  3. Genetic code is degenerate/mutation is in an intron
  4. Changes AA but no effect on 3º structure
  5. (New allele) is recessive so doesn’t influence phenotype
  6. Results in change in polypeptide that positively changes the properties (of the protein)
  7. May result in increased survival/reproductive success
26
Q

Describe crossing over and explain how it increases genetic diversity (4)

A
  1. Homologous pairs of chromosomes associate/form a bivalent
  2. Chiasma(ta) form
  3. (Equal) lengths of (non-sister) chromatids/alleles are exchanged
  4. Producing new combinations of alleles
27
Q

Explain why it is more useful to calculate index of diversity than to record species richness (2)

A
  1. Measures abundance/number/population of EACH species
  2. May be many/few of some species
28
Q

Give one way in which sampling procedures could be standardised

A

Same size of area
Size size net/mesh
Same sampling time
Samples taken at same time of day/on the same day

Biology (42 decks)

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