c8- diseases (test 1 only) Flashcards
1
Q
What is independent assortment- what does it mean and what does it do
A
(sexual reproduction)
- variation in cells
- everyone has different DNA except identical twins
2
Q
Compare genetic variability in sexually and asexually reproduced organisms, considering their adaptivity in the natural environment.
A
Sexual reproduction:
- adaptive advantages because the offsprings are genetically variable
ABLE TO SURVIVE IN CHANGING CLIMATE MORE EFFECTIVELY
- Some individuals may be better suited to the prevailing environment than others and will produce more offspring
Asexual reproduction:
- Allows populations of well-adapted clones to increase quickly in favorable environments
- clones may be more vulnerable than others when the environment changes
- As they cannot produce variable offspring they may be outcompeted by other better-suited clonal lines
3
Q
Some organisms reproduce sexually while others reproduce asexually. Give an example of each type of reproduction.
A
S: elephant…
A: paramecium, bacteria
4
Q
State advantages and disadvantages of asexual and sexual reproduction.
A
Advantages:
Asexual- no need for a mate to reproduce
- efficiency of reproduction (speed)
Sexual - variation in population
Disadvantages:
Asexual- disease could wipe out population rapidly
- not able to adapt to changing environment
Sexual- takes long to find mate
BINARY FISSION
5
Q
The position of a gene on a chromosome is…
A
the locus.
6
Q
Recombination
A
Crossing over
7
Q
Mutations
A
Changes in the base sequence of DNA
- Only way a brand new gene can enter the population
- changes can be HELPFUL, HARMFUL, or NEUTRAL
8
Q
Mutations can be: (where it occurs)
A
- Gametic: in the gametes of the organism, MEANS IT CAN BE PASSED ONTO EVERY SINGLE GENERATION AFTERWARDS
- Somatic: occurs only in the somatic/ autosomal/ body cells of the organism. THESE MUTATIONS CANNOT BE PASSED ON TO THE NEXT GENERATION. e.g. cancer
9
Q
Heterozygous
A
The dominant allele is expressed and the recessive allele is masked.
10
Q
Codominance, provide some examples
A
- a condition which the alleles of a gene pair in a heterozygote are fully expressed, resulting in offspring with a phenotype that is neither dominant nor recessive
- e.g. ABO blood group system-> person having A allele and B allele will have a blood type AB because both the A and B alleles are codominant with each other
- e.g. red flower crossed with a white flower produces red and white spots (both fully expressed)
11
Q
Incomplete/ partial dominance, provide some examples
A
A kind of dominance occurs in heterozygotes in which the dominant allele is only partially expressed and usually results in an offspring with an intermediate phenotype.
E.g. white flower + red flower = pink flower
12
Q
Sex linkage/ X-linked, what is it and provide some examples
A
A condition in which a characteristic that manifests more frequently in one sex than in the other is associated with the genes located in the sex chromosome.
E.g. color-blindness, bees
13
Q
Monohybrid crosses
A
One trait studied.
14
Q
AA
A
homozygous dominant
15
Q
Phenotype
A
What it looks like (the genetic makeup)
16
Q
Genotype
A
The letters
17
Q
aa
A
homozygous recessive
18
Q
Pp
A
heterozygous
19
Q
Trait suddenly appears= ?
A
recessive trait
Which was masked by last generation parents
20
Q
Selfing, with example
A
Crossing with itself (mostly in flowers) to find whether it is homozygous or heterozygous
2 red flower-> 3 red, 1 white-> parents are heterozygous
21
Q
Show what these labels mean in labeling crosses:
P
F1
F2
A
parental cross
first generation
next generation
22
Q
When pure bleeding red-flowered snapdragons are crossed with pure breeding white-flowered snapdragons, the resulting F1 offspring have pink flowers.
What is the expected genotype and phenotype of the F2 offspring when these F1 pink-flowered plants are crossed with the red parent? Show all working. (3 marks)
A
F2 parents: Rr x R for cross
Offspring RR 50% red
RW 50 % pink
23
Q
Describe the notation used when doing mendelian inheritance.
A
do a capital letter and a lower case letter, capital dominant, lowercase recessive.
When doing co-dominant or incomplete dominance, do two capital letters, e.g. red with white= RR WW (one isn’t dominant over another
24
Q
Autosomal dominant inheritance
A
Dominant gene located on 1 of the autosomes.
Passed onto males and females
Does not skip generation
E.g. Huntington’s disease, Marfan syndrone
25
Autosomal recessive inheritance, Provide example
- can skip a generation
- if both parents have the trait then all offspring will also have the trait. Parents are both homozygous.
E.g. cystic fibrosis
26
Sex-linked inheritance
Genes are carried on the sex chromosomes (X or Y
27
Sex linked inheritance dominant, provide example
- affected males pass onto all daughters
- more females than males
- e.g. dwarfism, rickets
28
Sex-linked inheritance recessive, provide some examples
- more males than females affected
- can skip generations
- affected female will pass it onto all her sons
- e.g. color-blindness
29
Rules for working out pedigrees
1. look for skipped generations (trait, no trait, trait again)
- see that= recessive
2. 2 people having a trait having a child who doesn't have a trait= dominant
- bc it's masking another trait
30
Biological theories of evolution
- Neo Darwinism modern theory
31
Evolution, what is it, what indicates it
Change in the gene pool of a population from generation to generation by such processes as mutation, natural selection, and genetic drift.
- if a change of genetic proportions occur, evolution has occurred
31
Five drivers of evolution
Five fingers of evolution:
1. Natural selection (adaptation)
2. Gene flow (migration)- new individuals immigrate, frequency changes (gene flow)
3. Mutation- brand new gene and trait added in mutation
4. Non-random mating (choosing mates based on characteristics of the opposite sex- e.g. peacocks choosing strong males- can devote energy to blooming, therefore have enough energy and strength
5. Genetic drift (small population)- population shrink, random chance
32
Microevolution
Change of a species over time.
33
Macroevolution
Going from one species to another species (diverge into another species)
34
Genetic definition of evolution
Evolutionary change is a consequence of changes in allele frequencies over time
35
Genetic drift
- Pinky (small population)
- Might eliminate a particular group
- Change in allele frequency due to random chance, often via natural disaster
- biggest impact on small populations
36
Allele flow/ gene flow
- pointer finger (gene flow/ migration)
- change in alleles frequency because individuals move among populations
37
Mutation
- only chance to get brand new allele
- changes DNA and get something totally new
- point, deletion, insertion
- beneficial, harmful, neutral
- with regard to fitness of alleles
- random
- rare
- random errors in the genetic code
38
Non-random mating
Occurs because individuals select mates based on their characteristics.
39
natural selection
Occurs because different genotypes have different fitness.
40
Fitness (genetics)
How well that mutation is suited to survival in that environment.
Good fitness= positive
Negative= bad mutation for its environment.
- depend on environment
- ability to survive and reproduce
41
Evolutional goals
- survive longer
- reproduce more
42
Increase chance of survival but decrease reproduce, provide example.
bats and frogs, suffer heavy predation by bats while singing to attract mates (but singing greatly increases no. of potential mates
43
Speciation (given two species, asked how speciation occurs)
- need the population to split and evolve in different directions for a long enough period
- isolation
- isolation mechanisms: prezygotic isolation, postzygotic isolation
44
Zygote
Fertilised egg
45
Geographic isolation
- what does it do
- example
E.g. Tasmania separate from Australia
- physical separation of population (by formation of a canyon, mountain, river, etc)
- leads to different adaptations on each side of barrier, eventually new species
46
What disrupts effect of geographic isolation?
Migration.
47
Types of prezygotic isolation.
Temporal isolation, behavioural isolation, mechanical isolation, gametic isolation (Sperm unable to fuse with egg as they evolved differently)
48
Describe the process of isolation.
1. starts off with a single population
2. there is population within that population, due to crossing over, independent assortment, and random mutation
3. some form of separation occurs, e.g. river forms (geographic), earthquake, sea level rise(TASMANIA), desert forms
4. evolution continues to occur in both populations (5 fingers)
5. different selective pressures act on each population, e.g. one population colder, one population hotter
6. natural selection causes these populations to evolve in different directions- divergent evolution
7. This happens until the two populations are so different, they can no longer interbreed and produce viable offspring (now two separate species)
LINK TO QUESTION
49
Increase population=?
increase chance to survive in the environment
50
Adaptations- provide examples
freshwater-> osmoregulation (contractile vacuole, dilute urine)
saltwater->
/
deserts-> sunken stomata in plants(humid environment in pit, decreasing conc gradient), longer loop of Henle in desert dwelling animals (absorb more water)
rainforest-> broad leaves in rainforest
/
- digestive system
- nitrogenous waste
51
What two types are colds and flus?
Bacteria- treat with antibiotics by breaking their cell wall
Viruses- antibiotics have no effect because they don't have cell wall, use antiviral treatments
52
Cancer, what are its 2 types
Cells can't stop replicating.
Malignant- harmful collection of cells
Benign- non-harmful
53
Chemo
kills fast-growing cells, toxins flowing through the blood.
53
Radiation
Targeted treatment, also kills surrounding cell tissue
54
Contagious cancer e.g.s
Tasmania devil facial tumor
- immune system doesn't kill invasive cell (cancerous cell from the other devil)
- maybe because they have a small population, all closely related therefore cannot identify if own cell
*no human cancers, little animal cancers are contagious
54
Give some examples of other diseases that aren't bacterial, viral infections and cancer (what causes them an what diseases specifically)
other diseases:
1. Fungal infections- tinea
2. Parasite- tapeworm infection
3. Prion diseases (mutated proteins affecting other proteins leading to a cascading effect)- Mad cow disease, Kuru
55
What is the difference between a bacteria and a virus? Give some examples of diseases of both.
Virus= not a cell, not alive, can only grow and reproduce within body of host
e.g. measles, chicken pox, Aids (HIV), hepatitis a,b,c, influenza
Bacteria= free-living cells that can reproduce outside body
e.g. tuberculosis, syphillis, flu(could be viral too), Lyme disease
56
Can you get the same virus repeatedly?
- cannot get the same virus twice
- body builds 'memory' of how to fight it, therefore able to kill it the second time
57
What are some bacterial killers? How do they kill?
Ammonia: disrupts bacterial cell membrane
Alcohol: breaks down proteins
Chlorine: destroys chemical bonds in bacteria
Iodine: stops proteins from working (kills bacteria that can get into the wound)
Penicillin: stops cell wall formation
58
Viruses
- extremely small, smaller than bacteria, non-living, disease-causing PATHOGEN that has the ability to infect any organism including bacteria
- composed of a protein coat (capsid) with either viral DNA/ RNA (not both)
- some have an additional membrane or envelope
59
What is a pathogen?
something that makes you sick, e.g. viruses and bacteria
60
Classification of viruses
1. whether or not they contain DNA or RNA
2. Their shape
3. What they infect
4. Their genetic make-up
5. The type of disease that they may cause
61
The group of viruses that infect bacteria are called _______
Bacteriophages
62
Two ways in which viruses reproduce.
1. Lytic:
- Direct way where the virus comes and injects its DNA into the bacteria
- viruses chop up bacterial DNA/ RNA, then takes over protein synthesis of the bacteria
- now producing a large amount of viruses, eventually ripping it apart and spreading viruses around.
- They can now infect other bacteria.
2. Lysogenic:
- infect bacteria by injecting their DNA
- Viral DNA implants itself inside bacterial DNA (plasmids - circular bits of DNA in bacteria)then it stops
- bacteria now copies its DNA and the (bacteria) plasmid's DNA multiple times
- hormonal (or temperature...) trigger causes viral DNA to pop out and makes the bacteria produce hundreds of thousands of viruses causing the bacteria to explode
*able to wait for optimal conditions to pop out
63
How does plasmid cloning link to insulin production?
- split by enzymes at certain areas and have extra DNA of humans placed in them and then joined by enzymes
- now copy the gene for the added DNA
64
Plasmids
1. small circular pieces of DNA that replicate independently from the host's chromosomal DNA
2. mainly found in bacteria
3. can exchange plasmids with other bacteria and get genetic variation occurring
4 can be split by enzymes at certain areas and have extra DNA (viral or human added) placed in them and then joined by enzymes. When plasmids replicate, they now copy the gene for the added DNA
5. use this for cloning and producing things like insulin, viruses use it to make copies of themselves
65
What are some examples of diseases caused by viruses?
- aids
- common cold
- rabies
66
Virus prevention
1. inactivated vaccine
- made of virus particles that have been killed and cannot replicate. The virus capsid proteins are still intact enough to be recognized by immune system and evoke a response
2. attenuated vaccine
- vaccine which uses "live"
3. antiviral drugs
67
Why are elderlies and babies especially vulnerable to viruses and are prioritized in vaccines?
babies do not have immunity
- therefore give them many vaccines
elderlies have damaged immune system
- therefore they get vaccines earlier too
68
Prions
- proteins that "have gone bad". They find their way into the brain and cause the proteins in the brain to change shape.
- these newly shaped proteins then create plagues or hard parts in the brain (brain is not suppose to have these plagues)
- e.g. kuru, mad cow, brain illnesses
69
Examples of prion disease
- Kuru
- found in cannibal tribe in PNG
- Men ate the meat of dead, women and children ate the brains
- lots died and found to have a prion disease
- some appear immune, could hold links to treatment
70
Viruses, living or non-living? (2 reasons for each)
Living:
- senses
- moves
- can reproduce adapt and evolve
Non-living:
- does not conduct cellular respiration on its own
- can't independently reproduce or evolve
71
whats the polymer and monomer of the prion structure function?
polymer= protein
monomer= amino acids
because prions are proteins gone bad
72
cystic fibrosis
autosomal recessive disorder- need both genes
- affects lungs and liver-> cannot osmoregulate
- due to deletion of 3 basis (1 codon gone)
- outside to inside barrier gets destroyed
73
What is the immune system?
- the body's defense against disease-causing organisms-> known as PATHOGENS, malfunctioning cells, and foreign particles
74
What is immunity?
The human body's ability to resist almost all types of organisms and toxins that tend to damage tissues and organs.
75
Vector
Something that carries a pathogen
E.g. mosquito (carrying pathogen malaria), ticks (carry bacteria), dogs (transmits rabies)
76
body has a three line defense against pathogens.
- body has a three-line defense system against pathogens
77
Two-line defense system
Non-specific/ innate immune responses: react the same way to all invaders
- includes chemical and physical barriers, e.g. skin, saliva, tears, mucus, cilia, stomach acids, urine flow, 'friendly' bacteria (first line)
(second line) scavenger white blood cells called neutrophils
- pathogenic microorganisms must make it past this first line of defense
- if this defense is broken, second line kicks in (lymphatic system)
78
What do pathogens include?
Prions, bacteria, viruses, protists, parasites, fungi
79
First lines of defense: skin
- What makes it an effective defense organism?
- forms waterproof mechanical barrier
- microorganisms that live all over skin can't get through your skin unless it's broken
- The dead, outer layer of skin, known as the epidermis, forms a shield against invaders and secretes chemicals that kill potential invaders
- You shed 40000- 50000 skin cells per day
80
First lines of defense: mucus and cilia
- What makes it an effective defense organism?
- As you breathe in, foreign particles (e.g. dust or smoke) and bacteria bump into mucus throughout your respiratory system and become stuck
(prevent them entering lungs which is a great diffusion surface for pathogens to enter blood)
- Cilia lines trachea and beat it back up after stuff got stuck in the mucus, to a point where it can be coughed back up
- over 90% of invaders are trapped by mucus and cilia
81
First lines of defense: saliva
- What makes it an effective defense organism?
- saliva contains any chemicals that break down bacteria.
- Lysozynes (proteins) in saliva make it easier for WBC to later engulf invaders
- Can't kill everything
82
First lines of defense: stomach acid
- What makes it an effective defense organism?
- swallowed bacteria and parasites are broken down by incredibly strong acids in the stomach that assist in breaking down your food
- the stomach produces a coating of special mucus to prevent acid from eating through the stomach and also prevents bacterial entry
83
First lines of defense: Tears
- What makes it an effective defense organism?
- wash pathogens out
- contains an antiseptic (lysozyme)
84
Pathogen elimination (actions)
Sneezing, coughing, vomiting, and diarrhea eliminates pathogens.
85
What are some other body secretions that eliminates pathogens?
- Sneezing, coughing, vomiting, and diarrhea
- Urine flow: flushes out pathogens from the bladder area
- Tears= contains antiseptic, washes them out
- 'Friendly' (beneficial) bacteria= grows on skin, bowel, mouth and gut, line walls to stop other harmful bacteria from growing, secrete toxins to kill pathogens
- Neutrophils= line 2, has 3 nuclei, are white blood cells that can find, kill, and ingest pathogens seeking an entrance into the body (*pus= dead neutrophils), shows strength of immune system
86
Which of the 3 lines of defense are specific and non-specific?
1. skin = non spec
2. inflammatory response = non spec
3. WBC = spec
87
Types of blood cells (red white)
Erythrocyte = red blood cell
Leukocyte= white blood cell
88
What is an example of an organism that reproduces both sexually and asexually and why?
aphids and water fleas (daphnia), reproduce asexually most of the time, but compensate for a lack of genetic variability by introducing short periods of sexual production as well.
89
Binary fission, with example of organism.
Binary fission is a method of asexual reproduction in which a single parent cell divides into two identical daughter cells. It is commonly seen in prokaryotic organisms like bacteria and archaea.
- genetically identical most of the time except for occasional genetic mutation that can occur at DNA replication
90
Budding, with example
Budding is a form of asexual reproduction in which a new organism develops as an outgrowth or "bud" from the body of the parent organism that is genetically identical.
This process is commonly observed in various organisms, including yeast, hydra, and some plants.
91
TASC 2022 Q23B
Some organisms can reproduce both sexually and asexually. In reference to one (1) image on
the previous page that shows both, explain the advantages of being able to undertake both
reproductive processes. (3 marks)
C, B or A (½) can be seen as organisms that are able reproduce both sexually and asexually.
Advantages of asexual reproduction include save time and energy (½) when
conditions are stable and well suited to identical genotypes (½). They do not need to
find a mate (½)
Advantages of asexual reproduction include the production of offspring that are
genetically diverse (½) which increases chances of survival for the species if
conditions are changing. (½)
92
TASC 2022 Q23C
Meiosis ensures that a wide range of genetic combinations occur during the formation of
gametes. The diagrams below show two processes that occur during meiosis.
Identify the two (2) processes shown in the diagrams below and how they contribute to genetic variation in gametes. (3 marks)
Process 1; crossing over or recombination (½). Homologous pairs can exchange
genetic material at the same allele/gene transferrin genetic material between paternal
and maternal chromosomes thus increasing genetic diversity. (1)
Process 2; independent assortment. (½) Homologous pairs can line up in different/
random order during meiotic divisions. This allows the maternal and paternal
chromosomes to be sorted into various different cells. This increases the possible
variations and DNA and thus increases genetic diversity. (1)
93
TASC 2022 Q24
Identify and analyse the changes in this population that occur over a period of time. (4 marks)
There is genetic variation in the original population i.e., some bacteria have a gene/allele that
is resistant to the antibiotic (1). Mutation may have been the source of this variation (½).
The antibiotic is the selection pressure (½). Resistant bacteria survive (½) to reproduce (½)
and pass the resistant allele/gene on to their offspring (½). Repeated use of the antibiotic
(½) leads to the population changing over time from being less resistant (more susceptible
population) to a more resistant population to the antibiotic.(½)
94
TASC 2022 Q25
c) Using an example evaluate whether this is an X-linked disease. Show any working. (2 marks)
As a recessive trait, any female who has the trait would have two affected alleles
XdXd, (1)thus would pass an affected allele to all sons who would be XdY and
affected.( ½) This is not the case as seen by I-2 who is affected, and has an unaffected
son II-4.( ½)
95
TASC 2022 Q25D
Show working to explain the probability of individuals I-1 and I-2 having a child with
polycystic kidney disease. (3 marks)
Working:
I-1 (DD or Dd) x I-2 (dd)
Note: based on given evidence, I-1 could be either heterozygous or homozygous
dominant, so there are 2 possibilities:
Option one:
D D
d Dd Dd
d Dd Dd
100% chance of an unaffected child (heterozygous, Dd), but all children would be
heterozygous/carriers for polycystic kidney disease.
Option two:
D d
d Dd dd
d Dd dd
50% chance of an unaffected child (heterozygous, Dd) and 50% chance of an affected
child (homozygous recessive, dd). However, the unaffected children would all be
heterozygous and carriers of the disease.
Either option for 3 marks
96
TASC 2022 Q27A
Name the overall process that is occurring. (1 mark)
Inflammatory process (1); second line of defence/ humoral response/non-specific
immune response/innate immune response (½)
97
TASC 2021
Question 22
The diagram below shows a method of reproduction that occurs in some plants.
a) Name the type of reproduction shown.
Asexual
98
Explain why the daughter plants are likely to have the same phenotype as the parent plant in budding?
Daughter plants result from mitosis (1), therefore genetically identical daughter plants (1)
to the parent plants.
Marks awarded for cloning / genotype / genetic make-up / only one parent, exact replicate
of parent plant.
99
TASC 2021 Q23A
Question 23
In cats, some aspects of the inheritance of fur colour are sex linked.
When a ginger male cat was crossed with a black female, all the female kittens were tortoiseshell
(a pattern of black hairs and ginger hairs) and all the male kittens were black.
However, in the reciprocal cross, although all the female kittens were again tortoiseshell, the male
kittens were ginger.
a) Complete the following genetic diagrams to explain the results of these two crosses.
ans in photos
100
TASC 2021 Q24B
Taking into account that it is recessive, is the trait sex-linked (on the X chromosome)
or not sex-linked (autosomal)? Justify your answer using evidence from specific crosses in
the family tree. (3 marks)
It appears to be sex-linked (1) because only males (½) have the trait. It appears that the trait is carried by the females, on the X chromosome (½).
Because males only inherit one X chromosome it is more prevalent in males, in fact no females can express the trait because the affected males die before passing it on by mating with a carrier female.
The trait is expressed by 13, having inherited it through his mother, 6, although the brother, 12, does not have it and this can be explained by them inheriting the unaffected X chromosome (1).
Not enough evidence to prove either sex linked or autosomal conclusively (½).
Answer should include reference to pedigree for full 3 marks or include a Punnett Square
to back up either argument
101
b) Why were no male tortoiseshell cats produced in crosses? (2 marks)
Tortoiseshell colouring can only occur where the two alleles, one with ginger and the other
black, are present together. These alleles are carried on the X chromosome and thus male
cats can only have one or the other, not both.
2 clear statements showing understanding of difference between male and female
tortoiseshell inheritance.
102
During the breeding season some male little penguins are known to mate with several
female birds and then return to their main burrow. Two chicks are hatched usually two days
apart and are raised by an adult male that may not be the father.
Suggest why this behaviour might be an advantage to little penguins. (3 marks)
Mating with several females;
* Increase in genetic diversity/ variation, larger gene pool (1).
(½)
* Increased chance for the [population] to adapt if conditions/ environment/ selection
pressures change (1)
* Adaptation due to favourable genes/ alleles/ characteristics being passed on (1)
* Population more likely to survive due to Natural Selection (1)
* More opportunity to breed therefore greater chance of a successful fertilisation (1)
* Non-biological father raising chicks
* More chicks looked after therefore a greater chance of survival (1)
* Reference to learned behaviours from the non-biological father was ignored
103
Waxy leaf frog (Phyllomedusa sauvagii). This species of
frog is found in hot, dry areas of South America.
It has glands that produce waxy lipids to spread over its skin. This reduces water loss.
Discuss how the process of natural selection has assisted the survival of the waxy tree
frog? (5 marks)
Genetic variation existed in the original population, with a frog having a mutation that had
glands that produce waxy lipids that spread over its skin.
There was an excess population of frogs, not all reach maturity.
The climate in the hot dry areas of South America was the selective pressure.
Frogs with waxy lipid glands had a selective advantage, less water loss to the hot dry climate.
They lived longer, reproduced more and passed on the favourable trait to their offspring.
Frogs without the waxy lipid glands mostly died before they reached reproductive age.
Over many generations the frogs all had the waxy lipid glands.
Hence natural selection has resulted in the waxy leaf frog adapting to survive in the climate.
104
(b) Explain how genetic variation may arise in this type of reproduction in this population. (2 marks
(b) Chance of mutation (1) in the copying during mitosis / cell division that leads to genetic variability (1).
105
Suppose a scientist transferred Bush Rats from New South Wales to Western Australia and
released them into a fenced area of coastal bushland that had Bush Rats already present.
If these groups were unable to interbreed and produce offspring, would you conclude that
the two populations were in fact separate species? Explain your answer. (2 marks)
Yes, these two populations of bush rats are separate species (1); a species can interbreed to produce fertile
offspring (½) and as these populations cannot, then they are a separate species/ speciation has occurred (½).
Also accepted: in a cline gene flow occurs between nearby populations, but may not occur between populations
at either end of the cline (½); as such, it is possible that bush rats from NSW and WA may not be able to
interbreed (½), but if these populations can both interbreed with populations from SA (or other location) (½)
then they could still be considered a cline rather than a separate species (½).
106
(a) How could you determine if the Bush Rat populations form a cline? (3 marks)
Within a cline there will be phenotypic/ visual/ structural/ size differences in the rats (½) which is due to
ecological/ geographical/ climatic differences in the regions where the populations are found (½). To test for the
presence of a cline, rats from two different populations/ from either end of the cline/ from NSW & WA (½) will
need to be interbred (½). If the rats from different populations can successfully reproduce (½) to produce fertile
offspring (½) then they are part of a cline. This may not be the case with populations of rats from the extreme
edges of the cline due to significant structural changes (½) however gene flow must occur between the different
populations of rats/ they must share a common gene pool which could be tested for using DNA/ genetic analysis
(½).
107
TASC 2020 Q19A
Based on this pedigree, explain why it is NOT possible for this condition to be inherited
through a sex-linked allele (X linked). (Use D and d as the alleles in your answer).(3 marks)
If it was X- linked inheritance, new coming dX
d
and she would have to inherit Xd
nly one X chromosome, it would have to be XD
X
DY, hence this cannot be a X-linked inheritance. (1) Males pass on the traits to their daughters and this does not
1) Hence it is not possible for this to be sex-linked.
(½) mark if students stated with evidence that it was a recessive pattern of inheritance.
OR,
Using any other pieces of evidence and referring to individuals in the pedigree
108
The Australian sheep blowfly is a serious pest in the wool and meat industries. In 1955 the
insecticide dieldrin was introduced to Australia. Sheep were bathed in a solution of dieldrin to
control sheep blowflies. When it was first used, dieldrin gave sheep twelve weeks’ protection
against blowflies. By 1958 dieldrin gave less than two weeks’ protection.
Explain the evolution of dieldrin-resistant blowflies, and in particular the role played by dieldrin in
it. (5 marks)
- Within the 1953 population of blowflies there was genetic variation as a result of random mutation (1)
- This resulted in a small percentage of the population being resistant to the dieldrin insecticide (1)
- The application of the dieldrin by the farmers became a sleective factor/ pressure/ agent for blwfly evolution (1)
- After first drenching/ bathing of sheep, surviving population of blowflies are able to breed and transfer resistant genes to the next generation- increasing % of individuals with alleles resistant to the effect of dieldrin(1)
- following repeated drenching/ bathing there is a significant increase in the population of flies resistant to the effects of deildrin (1)
- frequency of resistant genes is increasing significantly as a result of the selection pressure- actively being selected for (1)- this is an example of natural or artificial selection (1/2)
- end result is a population of insects in which a significant number carry the resistant gene- which will significantly lessen the impact of further drenching and less protection against dieldrin (1)
- application of dieldrin removed the non-resistant allele from the gene pool (1/2)
- the relatively short life cycle of the blowfly means that evolutionary processes occur relatively quickly and can be observed within three years. (1/2)
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Question 26
The map shows the natural distribution of a mammal, the red-necked wallaby, Macropus
rufogriseus.
Give two carefully explained reasons why populations of this species in Tasmania have NOT evolved into a separate species despite being geographically isolated by the waters of Bass Strait.
(4 marks)
Reason 1
The populations of red-necked wallabies in Tasmania have not been isolated long enough from the populations of red-necked wallabies on the mainland for sufficient genetic differences/ drift to accumulate. No differences in gene pool and frequency of alleles(2)
Reason 2:
The populations of the red-necked wallabies occupy similar habitats (even though geographically separate) so similar selection pressures meaning neither population needs to adapt differently. E.g. no climate variation/ competition/ predation factors. (2)
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On a ship at sea there is an outbreak of disease affecting the human digestive system.
Using examples, explain how cleanliness in food, water and personal hygiene practices on the
ship could assist in controlling this disease. (3 marks)
Diseases like this can be transmitted from person to person or person to food or people. The spread of the disease can be minimised by:
- washing hands immediately after going to the toilet/ before handling food so that pathogens are removed from hands.
- drink bottled water or tap water that has been boiled or chemically treated to kill pathogens.
- ensure kitchen surfaces utensils are hygienic/ cleaned with disinfectant to remove pathogens
- wash and cook food correctly to ensure that pathogens are killed.
- isolate/ quarantine people affacted to contain the disease
- use antiseptic wipes to remove pathogens from common fomites such as door handles and taps
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TASC 2019 Q23B
b. Which pedigree represents an X-linked dominant trait?
Your choice:
Explain your choice fully. (4 marks)
photos
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Among the mainland's populations of Bynoe's gecko Heteronotia binoei (a small type of lizard) are
several all-female populations which reproduce asexually in a process called parthenogenesis
where the offspring develop from unfertilised eggs.
a. Give TWO selective advantages for such populations. (2 marks)
- enables the gecko to reproduce very quickly and produce a greater quantity of offspring; increases population size
- doesn't require the effort to find a mate- saves time and energy especially in a dry environment
- can breed rapidly in suitable conditions
- if gecko is well adapted to the environment, then genetically identocal offspring will be also.
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Among the mainland's populations of Bynoe's gecko Heteronotia binoei (a small type of lizard) are
several all-female populations which reproduce asexually in a process called parthenogenesis
where the offspring develop from unfertilised eggs.
A university researcher has found that these females, however, appeared to be less able to
survive adverse conditions such as drought, flood and when food is scarce.
Give ONE good biological explanation for this. (2 marks)
Lack of genetic diversity in gene pool as offspring are genetically identical (1). hence no potentially suitable genetic variants that coul be favoured by natural selection when conditions change and become adverse (1)
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Rattus fuscipes
what's the first term and second term?
1. Genus
2. Species
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What are fungi?
Eukaryotic organisms that reproduce by forming spores.
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What are protists?
Eukaryotic unicellular organism
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Genetics c8 2016 q2a
(a) If the allele for white is sex linked recessive,
III 1 must be homozygous white (½)
One of her alleles for white would have to come via an X chromosome from II 2 (1)
Being male, he would only have one X chromosome (1)
Hence he would be white (½). This contradicts the given data.
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Genetics c8 2016 q2b
Explain why the allele for white coat color cannot be x-linked dominant (2 marks).
(b) If the allele for white is sex linked dominant,
I 1’s single X chromosome would carry the dominant allele for white (1)
This X chromosome would be passed on to II 1 (1)
II 1 should be white also (1). This contradicts the given data.
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Genetics c8 2016 q4i
(i) Two alternative answers were accepted, provided adequate justification was given. The first being the more correct based on all the information given. Dominant. Individuals 3 and 7 are most likely to be homozygous 'no trait' because they have no history of the trait within their families. Both these individuals have produced offspring with the trait. Thus their 'no trait' gene must be recessive and the gene for the trait dominant.
OR
Insufficient information to decide. Parents, one with and one without a trait, can produce offspring of either phenotypes (theoretical ratio 1:1) provided that one parent is homozygous recessive and another that is heterozygous (Aa x aa). This is consistent with the families of 1 & 2, 3 & 4 and 6 & 7 in the pedigree. However it is not possible to tell from this type of cross which parent is homozygous and which is heterozygous and hence it is not possible to determine which allele is dominant.
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Genetics c8 2016 q4
Can you determine if the trait is sex linked or not? Carefully explain your reasons. (2 marks)
The trait is not sex linked. If the trait is dominant, individual 9 could not have received this allele from his mother. Sex linked genes are carried on the X chromosome. Male offspring, being XY obtain their Y chromosome from their father and their X chromosome from their mother. If recessive, individual 1 would have to have the trait (allele on his single X chromosome) to produce a daughter (no. 5), who is homozygous recessive for the trait.
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Genetics c8 2016 q5b
Is the gene sex linked?
Cannot be sex linked (1/2) as males in the second generation do not exhibit the trait. (1) All males in the second generation have received the recessive gene from their mother, if the trait was sex linked recessive it would not have been masked by the Y chromosome and would show up in the offspring. (1 ½ )
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Malaria is a disease transmitted by mosquitoes. It is caused by a protist called plasmodium. Distinguish between viruses and protists. (3 marks)
Virus – not living, can’t reproduce with out using anothers ribosomes to produce its proteins
Protist – living, has membrane bound organelles and can reproduce by itself.
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C8 test 2 q7a
What evidence in their ranges suggests that the three armadillos belong to different species? (1 mark)
(a) (i) there are no fertile hybrids found in the overlapping regions; (1 mark)
