Forgotten concepts

Question 1

Monoclonal Antibodies:

Answer 1

antibodies produced in a laboratory that bind to a specific antigen and can be used to target specific types of parts of cells for a variety of therapeutic purposes

• Able to treat cancer and autoimmune diseases due to their ability to trigger the killing of cancerous or self recognizing cells respectively

Question 2

How to use Radio isotopic dating:

Answer 2

• Determine the quantity of a radioisotope in volcanic rock near the fossil and compare this to the quantity of the same radioisotope in the fossil
  
  • Use the known half life value of the radioisotope to determine the age of the fossil

Question 3

Features of a transition Fossil:

Answer 3

• It displays features of both common ancestors and its descendants
• It would need to be dated to have existed after the earliest descendant and before the latest ancestor

Question 4

Humoral Immune Response:

Answer 4

1. • A pathogen with an antigen that is complementary in shape to the antigen binding site on the receptor of a B cell interacts with that B cell.
   • When this occurs, the B cell is said to have been selected
   2. • Once a B cell has been selected, a T helper cell is selected through antigen presentation which also has a complementary receptor to the antigen
      • The complementary receptor to the antigen will recognise the selected B cell and secrete a number of different cytokines and interleukins
      • These cytokines cause the B cell to undergo clonal expansion through which many copies of the selected B cell are produced
   3. • The T helper cell also then stimulates the selected B cell via cytokines to undergo the process of differentiation
      • B cells are driven to differentiate into B memory cells and Plasma cells
   4. • After differentiating, plasma cells secrete antibodies into the blood in order to defend against the selected pathogen
      • B memory cells reside in the body for a prolonged period of time and are responsible for immunological memory

Question 5

Cell Mediated Immunity Response

Answer 5

1. • As T Helper Cells are selected, antigen presenting cells come upon a naive T Cell with a T receptor matching the antigen, initiating clonal selection
   • The naive T cell becomes selected and is stimulated by cytokines, from the T Helper Cell, to help undergo the process of clonal expansion and differentiation
   • The new clones differentiate into cytotoxic T cells and T memory Cells(same as B memory Cells - immunological memory)
   • Majority of new clones differentiate into cytotoxic T cells however which leaves the lymph node to travel through the body and eventually reach the site of infection
   3. • The cytotoxic cells arriving at the infection site all have T cell receptors specific to the foreign antigen
      • Upon finding an abnormal cell presenting complementary foreign antigens on its MHC I , the cytotoxic T cell binds to the abnormal cell via interactions between the T cell receptor and the antigen MHC I complex
        Chemicals such as perforin are secreted by the cytotoxic T cell to induce apoptosis

Question 6

Functions of the Lymphatic System:

Answer 6

• The transportation of antigen-presenting cells to the secondary lymphoid tissues for antigen recognition and initiation of the adaptive immune response
  • Production of leukocytes, including lymphocytes
  • Removal of fluid from tissue around the body
• Absorption of fatty acids from the digestive system

Question 7

Stages of the Lymphatic System:

Answer 7

Lymphatic Drainage:
- Fluid from blood vessels is constantly leaking into tissues and is increased during an inflammatory response
- Lymphatic capillaries collect that increased fluid that has leaked into the tissue as well as any pathogens
- Upon entering the lymphatic capillaries, the fluid is known as lymph and it is carried away into the lymphatic system where it eventually reaches a lymph node

Lymphatic Flow:
- The small lymphatic capillaries gradually join together to form larger vessels containing increasing amounts of lymph
- Due to them having thin walls, lymphatic vessels rely on surrounding muscle movements to squeeze lymph fluid throughout the system, not the heart
- Lymph vessels also have one way valves to only allow lymph fluid being pumped towards lymph nodes and away from tissues

Lymphatic Surveillance:
- The fluid drained from tissue reaches the lymph nodes via afferent lymphatic vessels
- The lymph then travels through clusters of B and T cells where antigen presenting cells and pathogens are likely to meet with a lymphocyte that has a matching antigen binding site, therefore stimulating the process of clonal selection
- If an adaptive immune response is then initiated, antibodies and activated cytotoxic T cells are transported in the lymph away from the lymph nodes via efferent lymphatic vessels
The lymph is then returned into circulation near the heart where the lymphatic vessels join with larger veins to be then pumped around the body

Question 8

Types of Radioisotopes for Absolute Dating(Carbon-14)

Answer 8

• ma form of absolute dating used to date organic(living) materials which has a half life of 5,730 years and dates material between 1,000-50,000 years
  • All living organisms have carbon containing organic matter and most of this is carbon -12 with a small amount of carbon -14
  • When alive, the C-12 and C-14 levels remains constant and equal to the C-12 and C-14 ratio in the atmosphere
    When the organism dies the C-14 decomposes into N-14, allowing scientists to determine how long ago it died by comparing the C-12 and C-14 ratio in the fossil to the ratio in the atmosphere(the longer ago the organism died, the less C-14 present)

Question 9

Types of Radioisotopes for Absolute Dating(Potassium-Argon)

Answer 9

• a form of absolute dating used to date igneous(volcanic) rock which has a half life of 1.3 billion years and dates material that is 100,000+ years old
• molten rock at 1000 degrees has small amounts of radioactive potassium and no argon
• when the rock starts to cool it solidfies and the argon accumulates from the decay of potassium isotopes
• A half life is when half the potassium 40 has broken down into argon

Question 10

Types of Radioisotopes for Absolute Dating(Potassium-Argon)

Answer 10

• a form of absolute dating used to date igneous(volcanic) rock which has a half life of 1.3 billion years and dates material that is 100,000+ years old
• molten rock at 1000 degrees has small amounts of radioactive potassium and no argon
• when the rock starts to cool it solidifies and the argon accumulates from the decay of potassium isotopes
• A half life is when half the potassium 40 has broken down into argon

Question 11

Other Types of Radioisotopes for Absolute Dating

Answer 11

Uranium 235-Lead-207: a form of absolute dating used to date uranium containing minerals such as shells or corals
- Dates between 1mya-4.5bya
- Has a half life of 700million years

Uranium 238-Lead 206: a form of absolute dating used to date uranium containing minerals such as shells or corals
- Dates between 1mya-4.5bya
- Has a half life of 4.5 billion years

Question 12

Characteristics of Hominins that changed over time and allowed for Bipedalism:

Answer 12

• Foranum magnum became more centrally located in humans allowing the head to rest on top of the spinal column providing balance while walking
  
  • Spine Curve: spine became more S shaped with a curve at the bottom and top to help vertical balance and walking
  • Rib cage: changed from funnel shaped to barrel shaped helping hominins maintain an upright posture for lengthy periods of time
  • Pelvis: became shallower and more bowl shaped which provides support for the upper body while standing and walking
  • Femur Angle: femur angle became larger allowing more weight to be distributed closer to the central axis giving more stability when walking
    Foot: Humans big toe become more protruding and the other toes became more aligned due to the decreased need to grasp. The foot arch increased making bipedal locomotion more efficient and the heel size increased increasing bipedalism energy efficiency

Question 13

Trends in Hominin Evolution

Answer 13

• Increased cranial Capacity as hominins evolved(only irregularity is that Neanderthalensis is slightly bigger than sapiens)
• Increased leg length in proportion to arms
• Increased size of medial and lateral condyles(bumps)
• Femur and Tibia join at an increased angle
• Pelvis becomes smaller and flatter
• Decreased Teeth size
• Mandible and Zygomatic arch have become finer
  Heel Bone has become bigger

Question 14

Characteristics of Primates:

Answer 14

• Forward facing eyes
  
  • coloured vision
  • Sexual Dimorphism
  • Flat Finger Nails
  • Opposable thumbs
  • Sensitive Fingertips
  • Relatively large brain
    Live in Social Groups

Question 15

Index Fossils must be:

Answer 15

• Physically distinctive
  
  • Had a large population
  • Have existed in many geographical areas
    Only lived within a known short period of time

Question 16

Mechanisms contributing to the modification of viral surface antigens:

Answer 16

Antigenic Drift: the small and gradual change in the gene encoding for viral surface antigens
- Normally memory cells will be able to recognise basic mutated surface antigens from previous viruses, however after multiple accumulated mutations, a new subtype is created, which is no longer recognised by the memory cells

Antigenic Shift: the sudden and significant mutation in the gene encoding for viral surface antigens
- Occurs when two or more different strains combine when coinfecting the same host, forming a new subtype through Viral Recombination
- Extremely infectious due to decreased ability to create natural immunity

Question 17

ELISA:

Answer 17

an experimental technique used to identify a pathogen by determining the presence of antigens or antibodies in a sample
- Types of ELISA tests; direct, indirect, sandwich and competitive

Sandwich Elisa Test Steps:
1. Antibodies specific to a pathogen are attached to a plate
2. The sample serum to be tested is then applied to the plate, resulting in any pathogen antigens present attaching to the antibodies
3. A second detention antibody linked to a colour changing enzyme is added, binding to any antibody-antigen complexes present
4. A substrate is added, reacting with the enzyme on the second antibody and changing colour/emitting a signal to reveal whether any pathogenic antigens were present in the sample

Question 18

How are Monoclonal Antibodies Produced:

Answer 18

1. • Scientists identify and isolate an antigen that is present on a desired target cell
   • This cell will typically be one that is responsible for causing the disease that scientists want to treat E.g. Cancer cell
   2. • Scientists vaccinate an animal usually mice with an antigen which stimulates an immune response and results in the selection and proliferation of a B lymphocyte to match the antigen
   3. • Scientists extract these B lymphocytes from the mice spleen
   4. • The extracted B lymphocytes are fused with rapidly dividing cancerous human plasma cells known as myeloma cells.
      • The products of this fusion are called hybridomas
   5. • Hybridomas are screened so that only the cells with the appropriate antibody are selected
      • They produce the specific antibody and are cloned resulting in mass production of these antibodies

Question 19

Role of Rubisco

Answer 19

Catalyses the following reactions

Carbon fixation: turns 3 CO2 and 5 RuBP molecules into 6x 3-PGA molecules.

Reduction: energy and hydrogen is donated from ATP and NADPH to convert 3-PGA into G3P. One G3P molecule is removed to form glucose.

Regeneration: ATP is used to convert 5G3P molecules into 3 RuBP molecules to restart the cycle.

Question 20

Process of Producing Recombinant Human Insulin:

Answer 20

1. .
   
   • 2 Plasmid Vectors are prepared which already contain the ampr gene for antibiotic resistance and lacZ the reporter gene and has the specific recognition site for the restriction endonuclease
   • The lacZ produces Beta-galactosidase, an enzyme which converts X-gal, a colourless compound to a blue
   2. .
      - Two plasmid vectors are used, one for insulin subunit A and B
      - An endonuclease such as BamHI cuts both the plasmids and the subunit A and B genes to form sticky ends
      - DNA ligase then joins each subunit gene to a separate plasmid at the sugar-phosphate backbone to create two recombinant plasmids.
   3. .
      - The plasmids are now added to a solution of E.coli bacteria and then either heat shock or electroporation can be used to increase the uptake of plasmids into the bacteria
   4. .
      - The bacteria cultures are spread and incubated onto agar plates containing X-gal and the antibiotic ampicillin
      - The colonies that for which are colourless can then be determined to be transformed bacteria with recombinant plasmids as the lacZ reporter gene is dysfunctional, meaning the gene of interest has been taken up
   5. .
      - The recombinant plasmids will produce an insulin subunit with a beta-galactosidase tail formed form the half of the lacZ gene which is transcribed and translated
   6. .
      - Transformed Bacteria that contain the recombinant plasmids are then placed into conditions to exponentially reproduce before their membranes are broken down to isolate the human insulin
   7. .
      The two insulin chains have their beta-galactosidase tails removed and are mixed together allowing the connecting disulphide bonds to form and create functional human insulin

Question 21

How to use CRISPR-Cas9 for gene editing

Answer 21

1. Synthetic sgRNA is created in a lab that has a complementary spacer to the target DNA that scientists wish to cut
   
   2. A Cas9 enzyme is obtained with an appropriate target PAM sequence
   3. Cas9 and sgRNA are added together in a mixture and bind together to create the CRISPR-Cas9 complex
   4. The sgRNA-Cas9 mixture is then injected into a specific cell, such as a zygote
   5. The Cas9 finds the target PAM sequence and checks whether the sgRNA aligns with the DNA
   6. Cas9 cuts the selected sequence of DNA
   7. The DNA has a blunt end cut that the cell will attempt to repair
      When repairing the DNA, the cell may introduce new nucleotides into the DNA at this site. Scientists may also inject new nucleotide sequences into the cell with the hope that it will ligate together