topic 4

Question 1

translation

Answer 1

mrna attach to ribosome
tRNA brings specifc amino acid
trna anticodon binds to mrna codon
AA join by peptide bonds using atp
trna released after AA joins polypeptide
ribosome move along mrna to form the polypeptide

Question 2

transcription

Answer 2

h bonds between dna bases break
1 strand acts as template
free rna nucleotides align by comp base pairs
rna u replaces t
rna polymerase joins adjacent nucleotides via condensation reaction forming phosphodiester bonds
pre mrna spliced to remove introns

Question 3

trna vs mrna

Answer 3

trna clover leaf mrna linear
h bonds in trna not in mrna
trna aa binding site mrna doesnt
trna anticodons mrna codons

Question 4

ribosome role in forming polypeptide

Answer 4

mrna bind to ribosome with space for two codons
allowing trna w anticodon to bind
catalyse formation of peptide bonds between amino acids

Question 5

mutation that changes the number of chromosomes

Answer 5

non disjunction
happens in meiosis
chromosomes fail to separate

Question 6

addition

Answer 6

cause frameshift
triplets move
more than one amino acid affected

Question 7

how can gene mutation have no effect on individual or positive change

Answer 7

change in nucleotide sequence formation of new alleles
no effect as degenerate or in introns amino acid sequence may change but not the tertiary structure
new allele recessive so doesnt influence phentoype
change to protien could lead to reproductive success

Question 8

how is chromosome number halved in meiosis

Answer 8

homologous chromsomes pair - one of each pair goes to daughter cell

Question 9

explain why all cells of body affected by mutation

Answer 9

mutation in gamete one extra chromosome in gamete
alleles derived from single cell by mitosis
mitosis produces genetically identical cells same dna and alleles

Question 10

why does allele frequency increase through generations

Answer 10

selective advantage reproduce and pass on alleles so allele frequency increases

Question 11

why might allele rapidly increase after selection already established

Answer 11

dominant allele so always expressed

Question 12

how does mutation occur without occurring in gene

Answer 12

mutation in promoter region coding for TF
lactase gene continues to be active

Question 13

genetic diversity number of Dif alleles of a gene in a population

Answer 13

number of Dif alleles of a gene in a population

Question 14

alleles

Answer 14

variation of a gene Dif dna base sequence and arise by mutation

Question 15

population

Answer 15

group of interbreeding individuals of the same species

Question 16

importance of genetic diversity

Answer 16

enables natural selection
as in certain environments new allele may benefit possessor
by resulting in change in polypeptide coded for that positively changes its properties
gives possessor selective advantage

Question 17

principles of natural selection

Answer 17

random gene mutation new allele of gene
certain envi new alleles may benefit possessor so organism has a selective adv
possessor ,ore likely to survive - reproductive success
adv allele inherited by offspring and over many generations alleles in frequency in population

Question 18

examples of aseptic techniques that can be used

Answer 18

wash hands with soap and disinfect surfaces to kill microbes
sterilise pipettes and boil agar to kill microbes
flame neck of bottle of bacteria to kill microbes
lift lid of Petri dish slightly preventing contamination
Bunsen burner close upward current of air draws air borne microbes away prev contamination

Question 19

method to investigate effect of antimicrobial substance

Answer 19

prep area - aseptic techniques
sterile pipette transfer bacteria from broth to agar plate using aseptic tehcnqiues
sterile spreader to spread bacteria evenly over agar plate
sterile forceps - same size discs that have been soaked in Dif conc of antimicrobials - same length time on agar plate
lightly tape lid onto plate and invert and incubate at 25c for 48hrs
measure diameter inhibition zone around each disk calc area pi r2

Question 20

why’s it important to maintain pure culture of bacteria

Answer 20

bacteria may outcompete bacteria being investigated
or harmful to humans

Question 21

hold lid with 2 pieces of tape

Answer 21

allows oxygen in preventing anaerobic bacteria growth
which are more likely to be harmful to humans

Question 22

incubate upside down

Answer 22

condensation drips onto lid rather than agar surface

Question 23

why not use higher conc of antimicrobial

Answer 23

more bacteria killed so clear zones may overlap

Question 24

presence of clear zone and absence

Answer 24

presence - antimicrobial diffuses oit disk into agar inhibiting growth of bacteria - more clear zones - more bacteria killed so more effective microbial
absence - bacteria resistant to antimicrobial or ineffective against that bacteria

Question 25

why cant 2 dif species breed to produce fertile offspring

Answer 25

dif species - dif chromosome no
offspring odd chromosomes so homologous chromosomes cant form
meiosis cant occur to produce gametes

Question 26

hierarchy

Answer 26

smaller groups into larger groups
no overlaps

Question 27

how is each species universally identified

Answer 27

binomial name - genus and species
universal so no confusion as many organisms have more than one common name

Question 28

2 advances helping to clarify evolutionary relationships between organisms

Answer 28

advances in genome sequencing compare dna base sequence , amino acid sequence , mrna sequence more dif more distant as more mutations build up overtime
advances in immunology comparing protein tertiary structure protein from one species bind to antibody against the same protein from another species

Question 29

biodiversity

Answer 29

variety of living organisms - habitats from small to large

Question 30

community

Answer 30

all pop of dif species living in same area

Question 31

species richness

Answer 31

measure of no of dif species in community

Question 32

index of diversity

Answer 32

relation between number of species in community and individuals in each species so takes into account if species present in small or large numbers

Question 33

farming techniques reduce biodiversity

Answer 33

remove woodland hedgerows or monoculture and herbicides to kill weeds
reduces variety of plants so fewer habitats and niches and fewer food sources

pesticides to kill weeds sp predator populations of pests decreases

Question 34

investigate diversity

Answer 34

compare frequency of measurable observable characteristics
base seq DNA MRNA AA seq
more differences more distant as mutations build up overtime so change in AA seq