chicken sperm Flashcards
compare prokaryotes and eukaryotes (9)
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explain how phospholipids properties help maintain the cell membrane structure (8)
phospholipid consisting of head + 2 tails
head: glycerol + phosphate
hydrophilic: attracted to water
tails: fatty acid chains
hydrophobic: not attracted to water but each other <3
leads to the formation of double layer in water → stability
heads are outer & attracted to water
tails in the middle & attracted to each other
attraction of non-polar tails to each other → in fluid state
allows vesicles to form or fuse with membrane
non-polar amino acid side chains attracted to hydrophobic tails
explain how vesicles are used to transport materials secreted by a cell (8)
proteins synthesised by ribosomes + rER
proteins are bound by vesicles
vesicles bud off from rER → transport proteins to Golgi apparatus → fuse with Golgi apparatus membranes
Golgi modifies proteins as they move along in vesicles
secretory vesicles bud off in trans Golgi → move across the cytoplasm → fuse with plasma membrane
exocytosis: release proteins outside the cell
rER + vesicle + plasma membrane have phospholipid bilayer structure
cells use vesicles to secrete substances
e.g. hormones and digestive enzyme
can contain cell products other than proteins
describe the events that occur during the cell cycle/mitosis (9)
interphase
G1: cell grows + organelles duplicate
S: DNA replication
G2: chromosomes begin condensing + prep for cell division
mitosis
prophase
chromosomes condense by supercoiling → sister chromatids visible
nuclear membrane breaks down
prophase + metaphase: spindle microtubules grow from poles to equator
metaphase
spindle microtubules attach to the centromeres
chromosomes line up at equator
anaphase
centromeres split
sister chromatids separate → dragged to opposite poles by the shortening of spindle microtubules
telophase
spindle microtubules disappear
nuclear membrane reforms around chromosomes → decondense
cytokinesis: cytoplasm divides → 2 daughter cells with identical nuclei
plant: cell plate form between nuclei
explain how the properties of water are significant to living organisms (9)
polar molecule
oxygen has a partial -ve charge + hydrogen has a partial +ve charge
hydrogen bonds form between adjacent water molecules
water remains liquid over wide range of temperatures
makes water a good solvent for polar/ionic substances
blood transport solutes in water
adhesive properties → transpiration stream and xylem
cohesive properties → high surface tension allowing insects to live on the surface
high specific heat capacity: moderates temperature fluctuation
high heat of vaporisation: sweating/transpiration cools organisms
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allows organisms to live below the surface
plants can photosynthesise
ice is less dense than water
surface of a body of water freezes first → organisms to survive in the water below
explain the factors that can affect enzymes (8)
substrate conc
substrate concentration ↑ → more frequent collisions between enzyme and substrate → enzymatic activity ↑
up to a maximal level of action → plateau → all active sites are occupied
temp
enzymes have an optimal temp
more frequent collisions between enzyme and substrate at higher temperatures → enzymatic activity ↑ as it gets closer to optimal temperature
high temps stop enzyme activity due to denaturation by changing active site shape
pH
enzymes have an optimal pH
enzymatic activity ↑ as pH gets closer to optimal pH
extreme pH stop enzyme activity due to denaturation by changing active site shape
explain the consequences of altering a DNA base in the genome of an organism (8)
altering a base in DNA = point mutation
only has an effect if base is in a gene
when mRNA is produced by transcription one mRNA base is different
one codon in mRNA is different
one amino acid is different in the polypeptide produced by translation of mRNA
degenerate: some base changes do not change the amino acid coded for
structure of polypeptide may be altered: usually does not function as well
gene mutation of haemoglobin by base substitution
antisense strand of DNA: CTC → CAC
sense strand of DNA: GAG → GTG
mRNA/transcription: GAG → GUG
amino acid/translation: glutamic acid → valine
in homozygotes: HbSHbS
RBC become sickle-shaped
↓ oxygen carried → oxygen stress
RBC bursts → block blood vessels → circulatory problems can cause organ failure
in heterozygous: HbAHbS → malaria resistance
explain how an error in meiosis can lead to Down’s syndrome (4)
trisomy of chromosome 21
non-disjunction during anaphase I/II in meiosis
I
metaphase: homologous chromosomes in equator
anaphase: separate → 1 pair doesn’t separate
telophase: cells divide into 2 → cells have either one more/less chromosome
II: sister chromatids fail to separate
fertilisation with 1 gamete carrying an extra chromosome
explain how reduction division results in genetic variety (8)
occurs during meiosis
cell undergoes meiosis I
homologous chromosomes pair up in equator
each chromosome in homologous pair came from maternal/paternal parent
randomly oriented to either side of cell
homologous chromosomes separate → cytokinesis
2 cells from 1st division undergo meiosis II: chromosomes separate again
1 cell → 4 cells
diploid number 2n → haploid number n
haploid cell contains only 1 chromosome from each original homologous pair
mixture of maternal & paternal chromosomes in any haploid cell is different
bc random orientation during meiosis → basis for 1st variety
outline the process of meiosis (6)
2 cell divisions: meiosis I + II
for production of gametes
chromosome number halved: diploid to haploid → 4 haploid cells
daughter cells different from parent cells
meiosis I
prophase
nuclear envelope breaks down
homologous chromosomes pair up → form chiasmata
crossing over occurs in non-sister chromatids
metaphase: homologous chromosomes line up at the equator of the spindle
attachment of microtubules to centromeres
anaphase: homologous chromosomes randomly orientated to opposite poles
telophase: chromosomes reach poles and unwind
nuclear envelopes do not reform bc meiosis II
meiosis II
prophase
chromosomes condense and become visible
new spindles form
metaphase: chromosomes line up at the equator of the spindle
attachment of microtubules to centromeres
anaphase: sister chromatids separate and move to opposite poles
telophase: chromatids reach poles and unwind
ALL HEMOPHILIA QUESTIONS (8)
hemophilia is due to a recessive allele
sex linked + X-linked: located on just one of the sex chromosomes (X)
Y chromosomes do not have the allele
female: XX → can have dominant & recessive → can be homozygous/heterozygous
male: XY → can only have dominant or recessive allele → only 1 copy so recessive allele is not masked → hemophilia is more common
conditions
males inherit X chromosome from mother → 50% chance if mother is a carrier
carrier is heterozygous for the gene → genotype XHXh
dominant allele masks the recessive allele
females inherit one X chromosome from father and one from mother
hemophilia allele could have been inherited from either parent
can have affected sons/carrier daughters
hemophiliac males have carrier daughters if mother pass on dominant allele but cannot pass the condition on to sons
affected father + carrier mother → affected homozygous recessive daughter → fatal
describe the inheritance of ABO blood groups (9)
one gene determines ABO blood groups
genes have different/alternative forms called alleles
there are three alleles (IA, IB and i) for this gene
example of multiple alleles, where 3 alleles can result in 4 phenotypes IAIA and IAi both give blood group A IBIB and IBi both give blood group B IAIB gives blood group AB ii gives blood group O
alleles that are codominant both affect the phenotype in a heterozygote
IA and IB are codominant
IA and IB are dominant over i
each individual has 2 alleles but only 1 is passed to offspring
example of a cross involving ABO blood groups
outline the use of polymerase chain reaction to copy and amplify minute quantities of DNA, including the role of Taq polymerase (2)
strands of DNA fragments split by heat
forms new double-stranded DNA by adding complementary nucleotides to split strands when cooling
Taq DNA polymerase can withstand high temperatures without denaturing
primers bind to targeted DNA sequences at lower temperature
heating and cooling cycle is repeated until enough DNA is obtained
example of PCR application: paternity cases, forensic investigations
outline the process of DNA profiling, including ways in which it can be used/to determine paternity (6)
DNA sample obtained from hair/blood/semen
amplified by PCR → cut into fragments by restriction enzymes
gel electrophoresis separates fragments according to size → produces a pattern of bands
patterns of bands from different sources are compared
pattern of bands is unique to the individual
↑ difference in pattern of bands → ↓ closely related the organisms are
used in cases of paternity/forensic investigations
DNA sample from child, mother and possible father(s) are taken
done for legal reasons/inheritance or for personal reasons/self-esteem issues for children/fathers/parents
analysed for matches between child with mother and possible father(s)
half the child’s bands should match the father
outline a basic technique for gene transfer (6)
plasmid used for gene transfer a small circle of DNA e.g. E. coli mRNA is extracted DNA copy of mRNA is made using reverse transcriptase
restriction endonucleases cut a small fragment of DNA from an organism
same restriction enzymes used to cut DNA of plasmid
sticky ends are the same in both cases
gene + plasmid mixed tgt → fragment of DNA is inserted into the plasmid
spliced together by ligase → recombinant DNA
recombinants can be inserted into host cell and cloned
e.g. E. coli is cultured → begins to make insulin
outline the features of ecosystems that make them sustainable (4)
recycling of nutrients between biotic and abiotic factors
e.g. carbon and nitrogen
decomposers break down organic matter and release inorganic nutrients
energy lost from ecosystems as heat → cannot be recycled → ongoing supply is needed from the sun
energy flow along food chains through trophic levels
autotrophs make food by photosynthesis
release oxygen for aerobic respiration
carbon dioxide for photosynthesis released by respiration
populations limited by food supply: regulated by neg feedback
supplies of water from rainfall: water cycle
outline the energy flow between trophic levels in a food chain (6)
light is the initial energy source for food chains
autotrophs convert light into chem energy thru photosynthesis to make glucose
energy flows through food chain by consumption
moves up trophic levels
producers → primary consumers → secondary consumers → tertiary consumers → detritivores/saprophytes/decomposers
energy conversions are inefficient energy lost in the form of heat by respiration in undigested food through the death of organisms only 10-20% is passed to next trophic level energy is not recycled in an ecosystem: only nutrients are
explain the cycling of carbon in an ecosystem (8)
carbon dioxide released by cell respiration of organisms
carbon pass along trophic levels
autotrophs fix carbon dioxide from atmosphere in photosynthesis to produce organic compounds
eaten by primary consumers → carbon compounds digested and absorbed
primary consumers eaten by secondary consumers
plants and animals die → decomposed by saprotrophic bacteria and fungi
combustion of fossil fuels releases carbon dioxide into the atmosphere
CH4 is produced by anaerobic respiration of biomass and methanogenic bacteria in cows
CH4 is oxidised to CO2 and water
peat is made from partially decomposed organic matter
volcanic eruptions add large quantities of carbon into the atmosphere
limestone are sinks of carbon
ALL ADAPTIVE RADIATION QUESTIONS (5)
happens in a group of species that evolve from a common ancestor
ancestral species occupies new environment with a variety of niches
different members of the species are exposed to different selection pressures → allele frequencies diverge
reproductive isolation enhances adaptive radiation → speciation
evolution of a similar structure in diff ways for diff functions adapted to new env
new species with common structures
homologous structures are evidence of adaptive radiation
comparative anatomy provides evidence for evolution
e.g. vertebrate pentadactyl limb = limb-bone pattern found in vertebrates
human hand adapted for manipulation of tools
seal’s forelimbs adapted for swimming
explain how the common ancestor might have given rise to two different species in different locations/speciation (4)
speciation = the splitting of a species into 2 separate populations
reproductive isolation due to geographic or behavioural isolation → gene pools separated
each group subjected to a different set of env conditions
differences in selective pressures → adaptive traits specific to the particular env conditions were selected by natural selection → gene pools diverge
evolve differently until genetic compositions are so different they cannot interbreed
speciation accumulating over long periods
punctuated equilibrium over a short time period
