Topic 3/4 Flashcards
Two differences between tissues and organs (2)
- Tissues made of cells, organs made of tissue
- tissue made of similar types of cells, organs made of different tissue
- Organs have more functions than tissuea
What is meant by the term polygenic inheritance? (2)
- Characteristics that show continuous variation are controlled by genes at many loci.
Significance of anaphase (1)
- Produce genetically different daughter cells from parent
Describe end result of mitosis in cell cycle (2)
- Chromatids separated
- Nucleus divided
Describe end result of S phase in cell cycle (2)
- DNA replicated
- Quantity of DNA doubled
Explain what is meant by the term sustainable (2)
- Resource that can be renewed/not run out
- Available to future generations
How has use of the Hardy Weinberg equation helped determine if evolution has taken place? (2)
- Identify changes in allele frequency over time
- If frequency has changed, evolution has taken place
How are breeding programs in zoos designed to reduce risk of inbreeding? (4)
- Selection of genetically different mates
- Use of mating records/stud books
- Exchange of animals between zoos
- Exchange of gametes between zoos
In reference to natural selection how might animals become extinct? (3)
- Predation/disease
- Change in environmental conditions
- Inability to reproduce
Define biodiversity (2)
- Genetic diversity within a range of species
Define niche (2)
- The way in which an organism interacts/exploits its habitat
Suggest how inbreeding can lead to genetic defects (2)
- Small gene pool as closely related animals mate
- Results in interbreeding depression, more homozygous genotypes
- Increased homozygous recessive genotypes for genetic defects
Use of Hardy Weinberg’s equation is only valid when what occurs? (1)
- Random mating
describe process of cell specialisation (4)
- Stimulus causes genes to become active
- Active genes are transcribed
- mRNA translated to produce proteins, change is permanent
- Proteins modify the cell
What are pluripotent stem cells? (3)
- Unspecialised cells that can differentiate to give rise to almost any cell in the body, except totipotent cells
- Some genes in pluripotent stem cells are inactivated meaning they can’t differentiate into all cell types.
Explain how organisms can be classified into taxonomic groups (2)
- Organisms with similar characteristics placed into same group
- Details of classification eg similarities in DNA, monocellular phylogeny and behavioural similarities.
How can independent assortment give rise to genetically varied gametes? (2)
- Random arrangement of chromosomes
- Chromosomes from homologous paris
How can organelle be identified as Golgi apparatus (3)
- Curved membrane bound sac
- Different size sacs
- Smooth surface, no ribosomes attached
Describe how society controls use of embryonic stem cells in medical research (4)
- Regulatory bodies like the high court set ethical aspects
- They judge what is acceptable based on codes of conduct
- Check source of stem cells is acceptable
- Enforce concept of human cloning being illegal
Describe and explain how the acrosome reaction prevents more than one sperm fertilising an egg (4)
- Sperm cell uses lysosomes to enter zona pellucid and fertilise egg cell
- Vesicles fuse with egg cell
- Cortical reaction is triggered, vesicles use exocytosis to release cortical granules
- Zona pellucida thickens
Cell membrane thickens and releases chemicals deterring sperm cells
Advantage of selecting various sizes of seeds for long-term storage (3)
- Maintain genetic diversity
- More chance of having beneficial alleles
- Increased chance of future survival if environment changes
Describe what seedbanks do to seeds to ensure long-term conservation of species (3)
- Assess seed viability, selecting seeds with living embryo
- Sterilisation of seed surface
- Drying seed and storing it at low temperatures
Explain how meiosis gives rise to genetic variation in gametes (2)
- Independent assortment gives rise to new combinations of paternal and maternal chromosomes
- Swapping over involves swapping over of chromosomes at centromeres
Why are placebos used to test efficiency of new drugs (2)
- Inactive or no drug is used as a control
- Psychological effects of taking the drug or placebo can be assessed
Describe the events of the anaphase stage in mitosis (2)
- Chromatids split
- Moved to opposite side of cell by spindle fibres shortening
How does crossing-over give rise to different combinations of alleles in gametes (2)
- Exchange of alleles between non-sister chromatids
Describe + explain features and functions of sperm cells (4)
- Many mitochondria provide ATP for swimming
- Flagellum - helps cell move towards ovum
Describe differences between species richness and genetic diversity (2)
- Species richness is number of species within a habitat
- Genetic diversity is number of alleles in one species
What is meant by molecular phylogeny (3)
- Molecular differences in DNA in proteins
- They are the evolutionary relationships between organisms
What is meant by gene locus (2)
- Location of gene on chromosome
How could species richness be measured (1)
- Count the number of species in the area of interest
Why use double-blind trials (1)
- To remove bias
What is an endemic species (1)
- Species found only in one specific geographical location
What structure is not present when cell undergoes mitosis (1)
- Nucleolus
Describe and explain 3 ways in which human sperm cell is specialised for its function (6)
- Streamlined shape reduces resistance when swimming
- Acrosome contains enzymes to digest the zona pellucida
- Haploid nucleus allows restoration of 46 chromosomes at fertilisation
- Large number of mitochondria provide energy for movement
- Flagellum allows cell to swim to ovum
- Receptors on cell surface membrane bind to egg cell membrane
What is meant by the term haploid nucleus? (2)
- Half the number of chromosomes found in a somatic cell
- One chromosome from each homologous pair
- Type of nucleus found in gametes
Suggest how captive breeding programs in zoos ensure genetic diversity is maintained in species (5)
- Captive breeding increases population size
- Stud books kept of breeding programs
- Zoos select mates
- Inter-exchange of animals between zoos for breeding, reduces risk of interbreeding
- Genetic diversity can be measured using DNA profiling
Describe what occurs during prophase (4)
- Chromatin condensed, chromosome becomes visible
- Nuclear membrane breaks down
- Nucleolus disappears
- Centrioles move to opposite poles and spindle fibres form
Suggest 3 factors that could affect survival chances of ferrets when reintroduced to their habitat (3)
- Availability of food or prey
- Intraspecific competition between other ferrets for resource
- Interspecific competition between other species for resource
What is meant by the term mitosis? (3)
- Involves prophase, metaphase, anaphase and telophase
- Produces two genetically identical nuclei to the original
Describe structure of cell wall in xylem vessel (4)
- Microfibrils consisting of cellulose held together by hydrogen bonds
- Lignin in cell walls for support and strength, could be spiralled or in a criss-cross pattern
- Bordered pits
- Pectin and hemicellulose also present in walls
Explain function of mitochondria in sperm cell (2)
- Site of aerobic respiration
- Provides energy in the form of ATP for movement
what is mean by the term ecological niche (1)
- organisms’ roles in the ecosystem
explain function of acrosome in sperm cell (2)
- Contains enzyme
- Digestion of zona pellucida
Describe the role of the Golgi apparatus (4)
- modifies proteins, eg addition of carbohydrate chains
- packages proteins in vesicles for transport out of the cell by exocytosis
- Name of vesicle pinched off Golgi is a lysosome
Smooth ER present in? (1)
- animal and plant cell only
Differences between pluripotent and totipotent stem cells (2)
- totipotent cells give rise to any type of cell
- pluripotent can’t give rise to all cells in body
- only totipotent cells can give rise to other totipotent cells
- Pluripotent can’t give rise to entire human being, totipotent can
Suggest how scientific ideas are critically evaluated (3)
- Scientists findings published in journa;s
- idea presented as scientific conferences and are peer reviewed
- other scientists report experiments to check validity and reliability
describe how you would use plant tissue culture to show totipotency in plant seedlings (4)
- Take seed cuttings
- Use agar medium with growth substances and regulatory hormones
- Use aseptic techniques when handling the culture, cover lid to prevent contamination
- Look too see if roots/leaves form
what is meant by double blind trial (2)
- One set of patients given drug, the other a placebo
- neither patient nor doctor knows if treatment contains drug or not
- removes bias from the results
Two events that take place during interphase (2)
- Synthesis of organelles
- Replication of DNA
name process that must occur in genetic material before chromosomes become visible (2)
- DNA replication
- DNA doubled
why are stem cells from bone marrow of patient able to repair damage to heart tissue of patient? (5)
- Stem cells are from the same person, no rejection
- stem cells receive stimulus from surrounding heart cells
- This causes certain genes to be activated, mRNA transcribed off active genes
- mRNA translated into protein on ribosome
- these proteins ensure the cell develops into heart cells
suggest why stem cells can be used to reverse paralysis from a spinal injury (2)
- Stem cells are totipotent and can give rise to specialised cells
- these can replace damaged cells
- the cells are capable of continuous division
3 structural differences between prokaryotic/eukaryotic cells (3)
- Eukaryotes have membrane bound organelles
- prokaryotes have plasmids, eukaryotes do not
- DNA in nucleus of eukaryotes
- DNA is linear in eukaryotes, circular in prokaryotes
describe how contamination of tissue culture is avoided (2)
- Aseptic techniques like heating the agar to kill off micro-organisms
- Used sterilised containers and equipment
- Seal container to prevent contamination
Explain why contamination of tissue culture is avoided (2)
- contaminants can cause infection to the plant culture
- contaminants compete for nutrients
- they can cause poor growth, decay or death
Why are drugs tested on animals and healthy humans (2)
- testing on animals for toxicity
- testing on healthy humans to determine side effects
- testing on humans to analyse how drug is metabolised
Describe structure of cellulose in cell wall (3)
- cellulose is a polymer of b-glucose
- cellulose held together by hydrogen bonds
- arrangement of microfibrils in criss-cross
- Presence of pectin
describe how structure of xylem vessels allow transport of water (2)
- Hallow and vessels are open at both ends
- vessels have pits and are strong so they don’t collapse
- Lignin provides waterproofing and strength to cell walls
Suggest how natural selection leads to evolution (5)
- Genetic variation within population
- selection pressure changes for example new frui on taller trees
- Animals with beneficial advantage of longer necks and legs are able to reach fruit on taller trees
- Organism with beneficial characteristic more likely to survive till adulthood and reproduce
- pass on advantaged genes to offspring
- Over time allele frequency changes and the population becomes isolated, could be geographically.
explain why bone marrow cells are source of stem cells (2)
- bone marrow contains unspecialised cells
- these are needed as they need to have the ability to differentiate into heart cells
Define tissue (2)
- group of cells
- Cells work together to achieve one function
how does lignin add strength to xylem tissue? (2)
- Lignin holds microfibrils together
- Lignin keeps microfibrils parallel
explain how calcium, nitrate and magnesium ions are used by plants (3)
- nitrates for production of amino acids
- Calcium for pectin
- magnesium for chlorophyll
Named process observed when undergoing meiosis not mitosis (2)
- Crossing-over
- chiasmata
Explain importance of nitrate ions in growth of plants (2)
- Amino acids
- Used in synthesis of DNA
- Amino acids used for synthesis of proteins
why are stem cells taken from patient and not anyone else (2)
- Cells are genetically identical
- No rejection
Devise an investigation to determine the effects of exposure time to agil on the rate of mitosis in onion root tips (6)
- use a controlled conc of agil eg 2moldm^-3
- Use the same age of onions
- Expose the roots for different time intervals eg 4, 8, 12, 16 hours
- prepare your root tip, cut tips and place them in hydrochloric acid for 5 minutes
- after rinsed place on microscope slide with a drop of toluidine blue stain
- count number of cells undergoing mitosis to calculate the miotic index
Describe how nitrate ions are transported from the roots to the leaves (2)
- Through Xylem vessel
- In water
Explain the effects of shortages in magnesium ions in plants (3)
- Limited chrolophyll production
- Lack of glucose due to less photosynthesis
- Plant leaves may be yellow
Explain why some bacteria can grow rapidly in skin wounds (3)
- Warm temp increase rate of reactions in bacteria
- Energy source from blood
- Water available for bacteria to function
Explain why starch must be broken down before being used by cells in growing plants (1)
- To produce glucose
- Used for respiration
Justify the continued functioning of SGSV (3)
- Conserves genetic diversity of crops
- Crops are protected from disease
- Help ensure future food security
Describe how each gamete recieves only one allele from each gene (2)
- In meiosis homologous chromosomes are separated from each other
- Chromatids are separated from each other
Describe two ways in which the structure of starch is related to its function (4)
- Made up of many glucose molecules
- Provides energy storage
- Large molecule so is unreactive
- compact so more can be stored
- branches allow rapid mobilisation
Name the part of a chromosome occupied by a gene (1)
locus
Explain how a group of cells can produce the same enzyme (3)
- Genes can be activated/deactivated
- Cells receive the same stimuli
- All cells have the same gene for enzyme activated
Even though offspring are from the same parents, explain why the offspring may be genetically different (2)
- Zygote formed from different gametes
- Each gametes contains different combination of alleles
- Due to independent assortment
explain why a second sperm cannot fertilise an egg cell (3)
- Cortical reaction
- Resulting in thickening of zona pellucida
- Other sperm cannot reach cell surface membrane
Compare and contrast clinical drug trials and William Withering’s soup trails (3)
- Both used different doses to deduce safe dose
- William did not use healthy volunteers, drug trails do
- William did not use placebo, drug trails do
Explain how the primary structure of collagen determines its properties (4)
- insoluble due to many hydrophobic R groups
- strong due to triplet helix
- many repeating amino acid sequences
- many small R groups so triple helix can form
explain how freezing sperm could affect the success of captive breeding programs (4)
- Sperm from different males frozen to increase genetic diversity
- frozen sperm always available if species numbers are too low
- freezing could result in poor viability, less successful fertilisations
- more sperm used if viability is low, reducing stocks
compare and contrast the structures of starch and glycogen (4)
- both polysaccharides
- both joined by glycosidic bonds
- starch consists of two polysaccharides, glycogen only 1
- starch has 1.4 and 1.6 glycosidic bonds, glycogen only has 1,6
