Human Bio Unit 4 - Common Exam Q (WACE)

What is gene therapy? (2 marks) (WATP 2024 SA)

- the replacement of an affected gene with a healthy gene
- in order to treat single gene disorders

Safest Answers for discussion of ethical considerations (2 marks)

ANY TWO OF:
Remain anonymous, data is confidential, data stored securely, informed written consent, right to withdraw, minimised harm, voluntary participation

Why is bacteria used as the framework of recombinant DNA technology (2 marks) (WATP 2024)

ANY TWO OF:
available in large numbers, reproduces quickly, only requires small amount of space, has been well studied, reproduces plasmids

STIMULUS:
Recent research indicates that the genetic variant linked to the risk of multiple sclerosis was brought to Europe about 5000 years ago by a migration of Yamnaya People, a group of herders from the Pontic Steppe in the Balkans and Western Asia. Scientists studied the DNA of 317 ancient skeletons and teeth and compared it to 410,000 specimens in the UK databank

QUESTION:
Explain how DNA sequencing, comparative genomics and bioinformatics would be used in this research (8 marks) (WATP 2024 ER)

DNA SEQUENCING:
- investigators would have collected DNA samples from each of the Yamnaya specimens
- then determined the nitrogen base sequence for the DNA of each specimen
COMPARATIVE GENOMICS (ANY 3 OF THE FOLLOWING):
- DNA sequences from the Yamnaya would have been compared to the UK specimens who had multiple sclerosis (MS)
- in order to see whether the Yamnaya carried the MS gene
- the more similar the DNA sequences the more closely related the Yamnaya were to the UK population
- and the more recent their common ancestors
BIOINFORMATICS (ANY 3 OF THE FOLLLOWING):
- the amount of DNA required to be compared for all the genomes is extremely large
- So the DNA data would be held and compared using computer technology
- which would more accurately be able to identify similarities and differences in the DNA sequences

STIMULUS:
Multiple sclerosis is an autoimmune disease, where the immune system has a strong response to the body's own cells. There is a suggestion this may have protected the Yamnaya from diseases found in the animals they herded.

QUESTION:
Using the research about Multiple scleriosis, explain how this demonstrates natural selection (12 marks) (WATP 2024 ER)

ANY 12 OF THE FOLLOWING:
- The Yamnaya show variation in having the gene/s for MS
- More Yamnaya are born then survive to maturity
- The Yamnaya usually maintain its numbers over time
- The MS gene is adaptive and aids survival of the Yamnaya
- the genes are selective forces
- So a struggle for existence between the Yamnaya occurs
- those with the genes for MS survive
- as they are not adversely affected by the diseases affecting their animals
- those without the gene for MS die from the disease of their animals
- the well adapted individuals reproduce
- and pass on thei gene/s for MS on to their offspring
- over time, the frequency for the gene/s for MS increases in the Yamnaya population

How could gene therapy and cell replacement therapy be combined as a treatment? (4 marks) (WACE 2017 SA)

- stem cells would be taken from the patient
- mutant gene is replaced by normal gene
- cells multiplied
- cells transferred back to the patient

Describe two situations where PCR could be used and the information that would be gathered (4 marks) (WACE 2018 SA)

ANY 2 OF THE FOLLOWING, 1 MK FOR NAME, 1 MK FOR DESCRIPTION:
- Early detection of infectious disease: foreign DNA from viruses/bacteria
- Tiny samples of DNA from fossils of extinct species: information for phylogenetic studies/relatedness, migration information
- Shortens time to detect hereditary diseases: amplify DNA to recognise faulty DNA/DNA that causes genetic disease
- DNA profiling/DNA fingerprinting: Comparing an individual's DNA to a library from known individuals
- DNA research: cloning/sequencing/patterns of gene expression/epigenetics
- Tissue typing: DNA matches for transplant organs

Explain how the technique gel electrophoresis separates DNA fragments of different sizes (4 marks) (WACE 2018 SA)

ANY 4 OF THE FOLLOWING:
- DNA fragments are placed in a gel
- A weak electric field is applied to the gel/positive and negative terminals
- This pulls the fragments to one end of the gel/fragments move to positive end
- Fragments move at different rates depending on size
- smallest fragments move faster/further/offer less resistance
- separates fragments into a unique pattern for that species

Describe the process of radiocarbon dating (4 marks) (WACE 2018 SA)

- Based on the decay of Carbon-14 to Nitrogen-14
- Amount of Carbon-14 is fixed at death
- The ratio of Carbon-14 to Carbon-12 determines the age
- Carbon-14 has a half life of 5730 years

STIMULUS: Mutations in the human genome can result from a variety of different causes. For each of the scenarios below explain how mutations are caused and the types of mutations produced. Provide an example to help clarify your answer:

Errors in DNA replication (7 marks) (WACE 2018 ER)

ANY 5 OF THE FOLLOWING:
- DNA replication is the process where new strands of DNA are made
- during replication (the DNA unzips and) complementary strands are formed
- can cause substitution/the wrong bases pair up during the process
- can cause deletions/DNA can be removed
- can cause insertions/DNA can be duplicated/extra DNA added
- can cause frameshifts/incomplete DNA code/unreadable DNA
- DNA that is formed undergoes cell division to create a new cell
- New cells have the wrong DNA code
ANY 1 OF THE FOLLOWING:
- Results in gene or chromosome mutation/can affect one gene or a whole gene
- results in somatic or germline mutations
EXAMPLE:
- cancerous cells/sickle-cell anaemia/silent mutations/Huntington's disease/cystic fibrosis

STIMULUS: Mutations in the human genome can result from a variety of different causes. For each of the scenarios below explain how mutations are caused and the types of mutations produced. Provide an example to help clarify your answer:

During cell division (7 marks) (WACE 2018 ER)

ANY 5 OF THE FOLLOWING:
- during cell division homologous chromosomes line up
- genetic material is swapped during cross over
- can cause inversions/chromosomes segment reversed
- can cause translocations/section of chromosome attaches to another
- extra chromosomes can be added to cells/cells can lose chromosomes/non-disjunction
- gametes produced have faulty chromosmes/incorrect number
ANY 1 OF THE FOLLOWING:
- results in chromosomal mutations/affects whole parts of chromosomes
- results in germline mutations/mutations can be passed on
EXAMPLE:
- down syndrome, XXY male, XO female

STIMULUS: Mutations in the human genome can result from a variety of different causes. For each of the scenarios below explain how mutations are caused and the types of mutations produced. Provide an example to help clarify your answer:

From damage caused by mutagens (6 marks) (WACE 2018 ER)

ANY 4 OF THE FOLLOWING:
- can resemble proteins and be incorporated into DNA
- can trigger DNA replication errors
- can cause DNA breakages/lengthening
- can block DNA replication/damage DNA structure
- can chemically react and modify DNA
- cells with damaged DNA multiply
ANY 1 OF THE FOLLOWING:
- results in gene and chromosomal mutations/can affect one gene or a whole part of a chromosome
- results in somatic or germline mutations
EXAMPLE:
- UV, mustard gas, ionising radiation, formaldehyde

Describe the process of recombinant DNA technology (10 marks) (WACE 2017 ER)

- The gene/segment of DNA is isolated/identified/located
- Cut by a restriction enzyme at
- recognition sites.
- The enzyme cuts the DNA on either side of the gene
- (The enzyme cuts the DNA) in a staggered cut
- Unpaired nucleotides overhang at the break
- Produced sticky ends
- A plasmid/a circular strand of DNA is removed from a bacterium
- The plasmid is cut with the same type of restriction enzyme
- Creates sticky ends.
- The sticky ends (of the isolated gene and the plasmid) are joined together Joined by DNA ligase
- The combined gene and plasmid are inserted into the bacterial cell/transformation occurs
- The bacterial cell is cloned/mitosis/divides
- Large amounts of the gene or its product is produced
- Multiplied/cultured/grown in vats before product can be harvested

ANY 10 OF THESE!!

Identify two ways in which hominids would have used Oldowan tools in their daily lives (2 marks) (WACE 2019 SA)

- 'chop' up meat/butchering/skinning
- dig up edible roots and plants
- crush/grind tough plant materials
- brake open animal bones

Explain how mutations can lead to changes in the allele frequencies of gene pools (3 marks) (WACE 2019 SA)

- mutations introduce new alleles into the population
- alleles may produce traits favourable to survival
- favourable traits will increase in number within the gene pool

Define DNA sequencing and state two ways in which the genomic information obtained by DNA sequencing of embryo cells could be useful (3 marks) (WACE 2019 SA)

DEFINITION
- DNA sequencing is a process to determine the order of the nucleotides in a gene or interest/sample of DNA

ANY TWO OF:
- establish long-term prognosis/identify disease-causing mutations/whether a person will develop an inherited disease
- family planning
- paternity/maternity testing

Explain how natural selection can lead to a particular phenotype becoming prevalent in a population (10 marks) (WACE 2019 ER)

VARIATION (1 MK, any one of the following):
- variation present in individuals/many phenotypes present
- wide variety of genes/large gene pool present

STRUGGLE (3 MKs, any 3 of the following):
- overproduction of offspring
- limited resources available
- selection pressure present
- competition for resources/struggle to survive

SELECTION (6 MARKS, any 6 of the following):
- genes passed to offspring
- a particular phenotype is more suitable for the environment
- individuals that do not possess the phenotype (genes) die-off
- individuals that do possess the phenotype (genes) survive/survival of the fittest
- over time more individuals have more suitable characteristics
- after many generations the particular phenotype is more prevalent
- can produce speciation

Outline the cause of alpha and beta thalassemia and identify what makes each type of thalassemia different (3 marks) (WACE 2020 SA)

- mutation of the gene responsible for red blood cells/haemoglobin production
- alpha - effects genes on chromosome 16/reduces the formation of alpha polypeptide chains/the alpha globin of red blood cells
- beta - effects genes on chromosome 11/reduces the formation of beta polypeptide chains/the beta globin of red blood cells

Alpha and beta thalassemia display the same inheritance pattern but can have differing effects on the gene pool of a population. Justify this statement (5 marks) (WACE 2020 SA)

- both are recessive traits
- heterozygotes are mildly affected with the disease/heterozygous carrier parents pass the traits onto their children
- homozygous condition in alpha thalassemia is fatal
- homozygous condition in beta thalassemia is severe but not fatal
- no homozygote alpha sufferers present in a population but there will be beta sufferers

How would hominins have manufactured Mousterian Tools (3 marks) (WACE 2020 SA)

- levallois technique/large flake removed from stone core
- flakes reworked edges/edges sharpened
- pressure flaking

Define the term 'DNA sequencing' and name and explain the method by which a DNA sequence is obtained today (7 marks) (WACE 2020 ER)

DEFINITION (1 mark):
- process of determining the order of nucleotides in the DNA

NAME OF PROCESS (1 mark):
- Gel electrophoresis/sanger sequencing

DESCRIPTION OF PROCESS (any 5 of the following):
- DNA sample undergoes PCR
- DNA polymerase added to primer
- fluorescents dideoxynucleotides (ddNTPs = ddATP + ddCTP + ddDTP + ddGTP) added to four reaction mixtures
- DNA terminated at different lengths
- four mixtures run separate lines
- DNA pieces are placed at one end of a bed of gel into wells
- an electric current is passed through the gel/a voltage is applied across the gel
- DNA is negatively charged so moves through the gel to the positive electrode
- DNA pieces move through the gel at different speeds/smaller DNA pieces move faster then large ones
- bands form which represent different segments/sizes of DNA

Describe the various types of mutations, identify the causes and describe how they can occur (15 marks) (WACE 2020 ER)

DEFINE (1 MK):
- a mutation is a change in a gene or a chromosome (leading to new characteristics in an organism or their offspring)

TYPES OF MUTATIONS (6 MKS):
- can be gene mutation or chromosomal mutations
- gene: changes in a single gene (which occurs during DNA replication)
- chromosomal: all or part of a chromosome is affected
- can be somatic or germline
- Somatic: mutations that occur in the body cells (reproductive cells are not affected) therefore mutation is not passed onto offspring
- Germline: mutations that occur in the reproductive cells/gametes therefore can be passed onto offspring

CAUSES (8 MKS):
MUTAGENS (2 mks):
- Could be caused by mutagens
Any one of the following:
- substances that are known to increase the rate at which mutations occur
- e.g ionising radiation, mustard gas, formaldehyde

DNA REPLICATION (3 mks):
- caused by errors in DNA replication
Any 2 of the following:
- deletion: part of a chromosome is lost
- duplication: section of chromosome is repeated/occurs twice
- insertions: DNA can be duplicated/extra DNA added
- frameshifts: incomplete DNA code/unreadable DNA code

CELL DIVISION (3 mks):
- cause by errors in cell division/meiosis
Any 2 of the following:
- inversion: broken part of chromosome joins back but in the wrong way
- translocation: part of chromosome breaks off and rejoins to the wrong chromosome
- non-disjunction: during meiosis, a chromosome pair does not separate so one daughter cell has an extra chromosome and one daughter cell has one less (aneulipody)

Explain how the example of the evolution of the unique hominin jaw illustrates the importance of mutations to evolution (5 marks) (2020 WACE ER)

- mutations introduce new alleles into population
- hominin jaw mutations must have been favourable/an advantage to survival
- organisms are better suited to bipedal locomotion/balance of head in bipedal locomotion/better for stereoscopic vision/helped to enable increases in cranial capacity
- favourable alleles passed onto offspring
- mutations maintained in population/future generations

How do gene and chromosomal mutations differ (2 marks) (WACE 2021 SA)

- gene mutations only affect one gene/small section of DNA
- chromosomal mutations affect more then one gene/part of a chromosome/whole chromosome

Explain how a favourable gene could lead to changes in the allele frequencies of a gene pool (4 marks) (WACE 2021 SA)

- mutations introduce new alleles into the population/mutations create variation
- alleles may produce traits favourable to survival
- favourable alleles are passed to offspring
- favourable traits will increase in number within the gene pool/natural selection will produce changes to gene pool

Explain how the high incidence of Tay Sachs within the Ashkenazi Jewish community in Australia is an example of the founder effect (4 marks) (WACE 2021 SA)

- Small original population/migration of small group to Australia
- with some (or one) individuals carrying the allele for Tay-Sachs disease
- restricted breeding with gene pool/cultural isolation
- frequency of allele increases over time

Explain, using examples, how the comparative studies of anatomy can be used for the construction of phylogenetic trees (10 marks) (WACE 2021 ER)

ANY 2 OF THE FOLLOWING EXAMPLES (ANY 2 OF COMPARATIVE EMBRYOLOGY, HOMOLOGOUS STRUCTURES OR VESTIGIAL ORGANS)

COMPARATIVE EMBRYOLOGY (5 marks):
- compare anatomical structure during embryo development/stages of embryo development from different species
- organisms share similar anatomical structures during early development
- indicates shared common ancestry/at one point they all shared an ancestor who had the basic structure
- more similar the structures are for longer in the embryonic stage = more closely placed on phylogenetic trees
- example: gill slits and tail found in vertebrate embryos

HOMOLOGOUS STRUCTURES (5 marks):
- compare anatomical structure from different species
- structures show a high degree of structural similarity but perform different functions
- indicates shared common ancestry/at one point they all shared an ancestor who had the basic structure
- more similar the structures are = more closely placed together on phylogenetic trees
- example: bone structure in the vertebrate limbs

VESTIGIAL ORGANS (5 marks):
- homologous structures that have a benefit/normal function in some species
- present but not functional in other species
- indicates shared common ancestry/at one point they all shared an ancestor who had the structure
- more shared features = more closely placed together on phylogenetic trees
- example - appendix/nicitating membrane/muscles to move ears/body hair/wisdom teeth in humans

Explain how an index fossil can be used to date another fossil (3 marks) (WACE 2022 SA)

- index fossils have a known date/age range
- due to widespread but limited time span they exist
- if found with other fossils, age can be correlated

What is some evidence from a fossil that an organism is arboreal (6 marks) (WACE 2022 ER)

ANY 4 OF:
- short clavicle (small collarbone)
- high shoulder blades
- longer arms/smaller arm to leg ratio
- long, curved fingers
- long thumbs/prehensile

WRITTEN EXPLANATION (2 MARKS):
- arms/shoulder adapted for swinging in the trees/circular arms movements/flexibility of arms to rotate through trees
- hands adapted to grip branches/hang from branches
NOTE: not adapted for brachiation

Describe the features of a fossil that allows you to conclude it would be bipedal (6 marks) (WACE 2022 ER)

ANY 3 OF THE FOLLOWING (1 MK FOR NAMING, 1 MK FOR DESCRIBING):
- long legs: allows for striding gait (2 marks)
- medial/lateral condyles of knee joint (femur) are large: allow for stability/weight bearing during walking
- wide pelvis/carrying angle present: allows for balance/stability
- robust heel/transverse and longitudinal arches of the feet/non-opposable big toe/aligned big toes: allows for stability/weight bearing/propulsion