exam questions t1-t4 Flashcards
teratozoospermia is a conditon that results in the sperm having an abnormal structure. the sperm would have two flagella. explain why production of these abnormal sperm cells would reduce fertility
- theres reduced mobility of the sperm/ reduced ability of sperm to propel itself
- could prevent the sperm from reaching the egg cell
- which prevents fertilisation
explain what is meant by a sex linked disorder
- disorder caused by a faulty gene
- located on the x or y chromosome
- so the disorder is most likely to effect one gender more than the other
DMD allele is found on the x chromosome. explain why genotype frequency for males with DMD cannot be calculated using the hardy weinburg equation
- male would only have one allele for the gene
- they cannot be heterozygous
- the hardy weinburg equation assumes all individuals have two alleles for the gene
explain why offspring from the same mother and father would be genetically different
- each zygote is formed from different gametes/random fertilisation
- each gamete contains diff combinations of alleles
- this is due to independant assortment and crossing over during meiosis
explain why you add HCl to the root tip squash experiment
- the HCl breaks down middle lamella
- this produces a thin layer of cells
- and it also allows light to pass through -> makes it easily visible
explain why you add a stain to the root tip in the experiment
- makes the chromosomes visible
- which means that the stages of mitosis can be identified
how can meiosis lead to genetic variation in gametes produced
- by independent assortment
- and by crossing over
explain why some genes show linkage and others show sex linkage
- there are more genes than there are chromosomes
- some genes are present on autosomal chromosomes so show linkage
- other genes are present on sex chromosomes and so would show sex linkage
how does crossing over produce gametes with new combinations of alleles on chromosomes
- the DNA sections are swapped between the chromosomes
- this results in chromatids with different combinations of alleles
how does independent assortment produce gametes with new combinations of alleles
- theres random orientation of homologous chromosome pairs
- different combinations of the chromosomes are then produced
give meaning of the term polygenic
- characteristic caused by multiple genes on multiple loci
- and it shows continuous variation
how does epigenetic changes affect the development of tissues in the embryo
- dna wrapped around histones
- histone modification effects binding of rna polymerase
- dna methlyation affects transcription of genes
- therefore the gene expression is altered
describe how cells become specialised
- chemical signals and transcription factors cause some genes to be ACTIVATED
- the mRNA is transcribed only from the activated genes
- the proteins are produced from the mRNA which causes modification of the structure and function of the cell
explain why stem cells from the heart cannot be used to grow cells to repair the cornea
- the cells arent totipotent
- this means that some genes are already activated and some are deactivated
- this would mean they cannot then specialise into cornea cells
why are chemicals from the eye needed to produce corneal cells from a suitable source of stem cells
- the chemicals cause genes to be activated and others to be deactivated/switched off
- the activated genes transcribe the SPECIFIC mRNA
- the specific mRNA synthesises the specific protein
- these proteins then cause the cells to develop into the corneal cells by modifying the structure and function of the cell to that of a corneal cell.
how can epigenetic changes cause differences in characteristics
- histone modification or DNA methylation effects activation of certain genes
- therefore effects the production of metabolic enzymes
explain how epigenetic changes can affect the activation of genes in daughter cells as pluripotent stem cells divide
- there are genes that are activated/deactivated in the stem cells
- due to histone modification and dna methylation
- therefore meaning that the same genes will be activated in the daughter cells
explain why an individual may have a greater height than their biological parents
- height is affected by environment as well as genotype
- this is a polygenic inheritance example
- this would mean that the individual can inheret multiple alleles from both parents that increase height
- there would also be environmental factors like having a higher protein diet that would increase their height as well
how to calculate tensile strength
divide cross sectional area by the force
explain the role of the middle lamella when a plant completes mitosis
the middle lamella gets produced between the adjacent new cells as it holds/sticks cell walls together
why does a sieve tube element not require rER and ribosomes
- no nucleus so no transcription or mRNA produced, also no ribosomes produced by the nucleolus, as no nucleus
- so no proteins are synthesised so no need to be processed by the rER
explain difference in number of mitochondria between the sieve tube elements and the companion cells
- cc has more mitochondria than the st
- this because role of st is to provide a channel for the transport of assimilites, so cellular contents kept to minimum
- but also the st has limited ability to carry out aerobic respiration
- so ATP is supplied to the st from the cc
state whats meant by term tensile strength
- pulling force that a fibre can withstand before breaking
describe arrangement of glucose monomers in cellulose molecule
- connected by 1,4 glucosidic bonds in beta glucose
- the alternate monomers are inverted due to the structure of beta glucose
explain why bacteria are able to multiply in the bloodstream when they enter the body
- warm conditions, water, glucose, amino acids and ideal pH is available
- suitable temp and pH for bacterial enzymes to work and act on
- the glucose in the blood can be used for respiration to provide energy
- and the amino acids can be used for growth
explain how breeding programmes in zoos maintain the genetic diversity of captive populations
- animals are selected to prevent breeding between closely related individuals
- a stud book is used to select the mating individuals
- theres the exchange of animals/gametes between zoos
explain why healthy volunteers are given different doses of a drug or placebo
- diff doses = determining of safe dose
- checking for side effects
- the placebo is used to make sure that the side effects experienced are due to the drug
the ebola vaccine was given to health workers and immediate family of those with the disease
justify the use of this vaccine even though the clinical trials had not been completed
- large numbers of people died from the disease
- health workers r most likely in contact with people with the disease
- the side effects of the vaccine are less severe than side effects of the acc disease
- vaccinating the immediate family will help reduce the spread of the disease
- if health workers are vaccinated they can help and care for more people
explain the role that a placebo and double blind trial have in producing valid conclusions
- placebo provides a control group for comparision which ensures that the side effects are acc due to the drug and not due to any psychologial effect
- double blind trial is when neither doctors or patients know who is getting the drug which ensures that bias is removed from the trial
why is agar plate incubated at 25 degrees celsius
- prevents growth of pathogenic strains that are harmful to humans
- but the temperature still allows for the bacteria to still multiply
advantage of drying seeds before storage
- drying removes moisture from the seeds
- increases storage time
- this because it reduces enzyme action, prevents decay or germination of the seed
justify benefits of conserving seeds
- prevents extinction of species
- can be reintroduced so improves biodiversity
- protects/safe guards genes that could be useful in the future
- could be consisting of potential medical values
explain why production of fibres from nettles is more sustainable than fibres produced from crude oil
- nettles are renewable as they can be grown quick
- crude oil is non renewable and so will run out quickly
- use of fibres from nettles will be able for future generations
- clothing made of nettle fibres is biodegradable
Describe the role of tRNA in the production of a protein
- tRNA molecules transport amino acids to the ribosome
- tRNA molecule has an anticodon that bonds to a codon on the mRNA
- each tRNA carries a particular amino acid
describe how the primary structure of a protein enables it to be soluble in water
- primary structure determines the folding of the polypeptide
- forming a globular structure
- the hydrophillic R groups are located facing outside/out of the protein
- the water forms hydrogen bonds with the hydrophillic groups
define gene
sequence of bases on DNA coding for a sequence of amino acids
describe differences between structure of DNA and RNA
- DNA has dexoyribose but RNA is ribose sugar
- RNA has uracil base instead of thymine
- DNA is double stranded but RNA is single stranded
compare and contrast process of transcription with DNA replication
- both involve forming phosphodiester bonds
- both involve the enzyme DNA helicase
- transcription: RNA polymerase and RNA nucleotides but DNA replication: DNA polymerase and DNA nucleotides
- replication produces double stranded DNA molecules whereas transcription produces single stranded RNA molecule
- replication produces identical copy but transcription produces a complementary copy
describe how a framshift mutation involves the insertion or removal of one or two nucleotides could result in the production of leptin with a variety of shorter primary structures
- adding or removing nucleotides changes the triplet code
- this could introduce a new stop codon
- which would code for a shorter sequence of amino acids
removing one base from a DNA sequence will affect the primary structure of a protein but changing one base for another may not affect the primary structure of a protein
explain why these two types of mutations have different effects on protein structure
- deletion could affect every codon -> frameshift mutation
- deletion more likely to affect the position of stop codon
- deletion results in diff sequence of amino acids
- substitution may code for same amino acid
- due to the degenerate nature of genetic code.
describe roles of transcription and translation in synthesis of a globular protein by a muscle cell
- the sequence of DNA/gene for globular protein is transcribed
- complementary base pairings between RNA ncleotides and DNA produce mRNA
- mRNA leaves the nucleus and attaches to a ribosome
- pairing between codons on mRNA and anticodons on tRNA
- tRNA provides specific amino acids
- sequence of bases determines the sequence of amino acids/ the primary structure of the protein.
plant species - has bright yellow leaves, and also greyish brown leaves
in areas where less people go, it is yellow but places where bulbls are collected in high numbers, there are greyish brown leaves. explain why areas where bulbs are collected have greyish brown leaves
- collection acts as a selection pressure
- as variation in colour exists due to genetic mutations, the brown colour offers better survival advantage
- they are less likely to be collected as they are harder to see
- they are more likely to survive, reproduce and pass on their alleles
- this increases allele frequency
