Voice of the Genome Flashcards
What are the two types of cells?
Prokaryotic and eukaryotic cells.
What are the main differences between prokaryotic and eukaryotic cells?
Eukaryotic cells are complex and include all animal and plant cells. Prokaryotic cells are smaller, simpler, and include bacteria.
What are organelles?
Organelles are parts of cells, each with a specific function.
How can we see the internal structure of most organelles?
By using an electron microscope.
What are the key structures of an animal cell?
Plasma membrane, nucleus, nuclear envelope, nucleolus, rough endoplasmic reticulum (RER), smooth endoplasmic reticulum (SER), ribosome, Golgi apparatus, lysosome, cytoplasm, mitochondrion, centriole.
What is the description of the nucleus?
A large organelle surrounded by a nuclear envelope (double membrane), which contains many pores. The nucleus contains chromatin (which is made from DNA and proteins) and a structure called the nucleolus.
What additional organelles do plant cells have?
Chloroplasts, a cell wall, and a large central vacuole.
What is the function of the nucleus?
The nucleus controls the cell’s activities by controlling the transcription of DNA DNA contains instructions to make proteins. The pores allow substances (e.g. RNA) to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.
What is the function of the lysosome?
Contains digestive enzymes.
These are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell.
What is the description of the lysosome?
A round organelle surrounded by a membrane, with no clear internal structure.
What is the function of the ribosome?
The site where proteins
are made.
What is the description of the ribosome?
A very small organelle that
either floats free in the
cytoplasm or is attached to the rough endoplasmic reticulum. It’s made up of proteins and RNA. It’s not surrounded by a membrane.
What is the description of the Rough Endoplasmic
Reticulum (RER)?
A system of membranes enclosing a fluid-filled space. The surface is covered with ribosomes.
What is the function of the Rough Endoplasmic
Reticulum (RER)?
Folds and processes proteins
that have been made at the
ribosomes.
What is the function of the Smooth Endoplasmic
Reticulum (SER) ?
Synthesises and processes lipids.
What is the description of the Smooth Endoplasmic
Reticulum (SER) ?
A system of membranes enclosing a fluid-filled space.
What is the description of the Golgi apparatus
A group of fluid-filled,
membrane-bound, flattened sacs. Vesicles are often seen at the edges of the sacs.
What is the function of the Mitochondrion
The site of aerobic respiration, where ATP is produced. They’re found in large numbers in cells that are very active and require a lot of energy.
What is the description of the Mitochondrion
They’re usually oval-shaped.
They have a double membrane — the inner one is folded to form structures called cristae. Inside is the matrix, which contains enzymes involved in respiration.
What is the description of the Centriole
Small, hollow cylinders,
made of microtubules (tiny
protein cylinders). Found in
animal cells, but only some
plant cells
What is the function of the Golgi apparatus
It processes and packages
new lipids and proteins.
It also makes lysosomes.
What is the function of the Centriole
Involved with the separation
of chromosomes during cell
division
Where are proteins made in a cell?
At the ribosomes.
What is the function of ribosomes on the rough ER compared to free ribosomes in the cytoplasm?
Ribosomes on the rough ER make proteins that are secreted or attached to the cell membrane, while free ribosomes make proteins that stay in the cytoplasm.
Whole process of organelles that are Involved in Protein Production and Transport
google doc
How are proteins transported from the ER to the Golgi apparatus?
In vesicles.
What happens to proteins produced at the rough ER?
They are folded and processed, such as having sugar chains added.
How are proteins transported out of the cell?
They enter vesicles that move to the cell surface, where they are secreted.
What happens to proteins at the Golgi apparatus?
They undergo further processing, such as sugar chain trimming or additions.
What is the structure of a prokaryotic cell’s DNA?
It is circular DNA, present as one long coiled-up strand, not attached to histone proteins.
What is the function of a prokaryotic cell’s flagellum?
It is a long, hair-like structure that rotates to move the cell. They dont all have one
What is the function of a prokaryotic cell’s capsule?
It is made of secreted slime and helps protect the cell from attacks by the immune system.
What is the function of pili in prokaryotic cells?
Pili help prokaryotes stick to other cells and can be used in the transfer of genetic
material between cells.
What are plasmids?
small loops of DNA that aren’t part of the main circular DNA molecule. Plasmids contain genes for things like antibiotic resistance, and can be passed between prokaryotes. Plasmids are not always present in prokaryotic cells. Some
prokaryotic cells have several.
What is a mesosome in a prokaryotic cell?
An inward fold of the plasma membrane, whose function is debated—some think it aids in processes like respiration, while others believe it is an artifact from electron microscopy.
What structures are present in eukaryotic cells?
Nucleus (contains DNA)
Membrane-bound organelles (e.g., mitochondria, Golgi apparatus, ER)
Ribosomes (larger than prokaryotic ribosomes)
Plasma membrane
Cell wall (in plants and fungi, made of cellulose or chitin)
Cytoplasm
Flagella or cilia (in some eukaryotic cells)
What structures are present in prokaryotic cells?
Circular DNA (free-floating in cytoplasm)
Plasmids (small loops of extra DNA)
No membrane-bound organelles
Ribosomes (smaller than eukaryotic ribosomes)
Plasma membrane
Cell wall (made of murein, a glycoprotein)
Cytoplasm
Flagellum (in some prokaryotic cells)
Pili (in some prokaryotic cells, used for attachment and DNA transfer)
Capsule (in some prokaryotic cells, helps protect against immune system)
What is the difference between magnification and resolution?
Magnification: How much bigger the image is compared to the actual specimen.
Resolution: The ability to distinguish between two objects that are close together.
What is the formula for magnification?
Magnification= size of the image/real size of object
What are the two main types of microscopes?
Light microscopes: Use light to form an image.
Electron microscopes: Use electrons to form an image.
What are the key features of a light microscope?
Uses light to form an image.
Maximum resolution of about 0.2 micrometers (μm).
Can view large organelles like ribosomes, ER, and lysosomes.
Maximum magnification is about ×1500.
What are the key features of an electron microscope?
Uses electrons to form an image.
Higher resolution than light microscopes.
Maximum resolution of about 0.0002 μm (1000 times higher than light microscopes).
Maximum magnification is about ×1,500,000.
How do you use an eyepiece graticule and stage micrometer to measure a specimen?
Line up the eyepiece graticule with the stage micrometer.
Note how many graticule divisions match a known micrometer length.
Calculate the size of one graticule division using:
Sizeofonegraticuledivision
=Stagemicrometerdivision/
Eyepiecegraticuledivisions
Use this value to measure specimens under different magnifications.
What is an eyepiece graticule and a stage micrometer?
Eyepiece graticule: A ruler inside the microscope eyepiece with no fixed units.
Stage micrometer: A microscope slide with an accurate scale (known units).
What are the two types of electron microscopes?
Transmission Electron Microscope (TEM):
Uses electromagnets to focus a beam of electrons through a specimen.
Produces high-resolution images of internal structures.
Can only be used on thin specimens.
Scanning Electron Microscope (SEM):
Scans a beam of electrons across the specimen.
Produces 3D images of the surface.SEMs are good because they can be used on thick specimens.
Lower resolution than TEM.
What is a cell?
The smallest unit of an
organism
What is a tissue?
A tissue is a group of similar cells that are specially adapted to work together to carry out a particular function.
What is cell organisation in multicellular organisms?
Multicellular organisms are made up of different cell types, which are organised into tissues (cells that perform the same job), organs (different tissues working together), and organ systems (different organs working together).
4 examples of tissues
Squamous epithelium, Ciliated epithelium, Xylem tissue and Cartilage
What is squamous epithelium?
Squamous epithelium is a single layer of flat cells in a surface, found in many places including the alveoli in the lungs.
What is ciliated epithelium?
Ciliated epithelium is a layer of cells covered in cilia (tiny hair-like structures) that help move substances along. It is found in places like the trachea, where it wafts mucus.
What is xylem tissue?
Xylem is a plant tissue with two jobs: it transports water around the plant and supports the plant. It contains xylem vessels and parenchyma cells fill the gaps.
What is cartilage?
Cartilage is a type of connective tissue found in the joints. It also shapes and supports the ears, nose, and windpipe.
What is an organ?
An organ is a group of different tissues that work together to perform a particular function.
What tissues make up a leaf?
Lower epidermis – contains stomata for gas exchange.
Spongy mesophyll – has spaces for gas circulation.
Palisade mesophyll – does most photosynthesis.
Xylem – carries water to the leaf.
Phloem – carries sugars away from the leaf.
Upper epidermis – covered in a waterproof waxy cuticle to reduce water loss.
What is an organ system?
An organ system is a group of organs that work together, each with a particular function.
What tissues make up the lungs?
Squamous epithelium tissue – surrounds the alveoli.
Fibrous connective tissue – helps force air out of the lungs when exhaling.
Endothelium tissue – makes up capillary walls around alveoli and lines large blood vessels.
What is the circulatory system?
The circulatory system consists of organs involved in blood supply, including the heart, arteries, veins, and capillaries.
What is the respiratory system?
The respiratory system consists of organs, tissues, and cells involved in breathing. It includes the lungs, trachea, larynx, nose, mouth, and diaphragm.
What is the overall organisation of multicellular organisms?
Similar cells group together to form tissues. Tissues work together to form organs. Organs work together to form organ systems.
What is mitosis?
Mitosis is a type of cell division in which a parent cell divides to produce two genetically identical daughter cells.
Why is mitosis important?
Mitosis is needed for the growth of multicellular organisms, repairing damaged tissues, and asexual reproduction.
What happens during prophase?
The chromosomes
condense, getting shorter and fatter. Tiny bundles of protein called
centrioles start moving to opposite ends of the cell, forming a network of
protein fibres across it called the spindle. The nuclear
envelope (the membrane around the nucleus) breaks
down and chromosomes lie free in the cytoplasm
What is the cell cycle?
The cell cycle consists of a period of cell growth and DNA replication called interphase, followed by mitosis.
What are the stages of interphase?
G₁ phase (Gap Phase 1): The cell grows, and new organelles and proteins are made.
S phase (Synthesis): The cell replicates its DNA, getting ready for mitosis.
G₂ phase (Gap Phase 2): The cell keeps growing, and proteins needed for division are made.
What are the four stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What are chromosomes joined by
centromere
What is a single chromosome strand called
Chromatid
When is a chromosome referred to as a sister chromatid
A sister chromatid refers to one of two identical copies of a chromosome while they are still attached at the centromere.Once the sister chromatids separate during cell division, they are called individual chromosomes.
What happens during metaphase?
The chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.
What happens during anaphase?
The centromeres divide, separating each pair of
sister chromatids. The spindles contract, pulling chromatids to opposite poles (ends) of the spindle, centromere first. This makes the chromatids appear v-shaped.
What happens during telophase?
The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They’re now called
chromosomes again. A nuclear envelope forms around each group of
chromosomes, so there are now two nuclei. The cytoplasm divides (cytokinesis) and there are now two daughter cells that are genetically identical to the original cell and to each other. Mitosis is finished and each daughter cell starts
the interphase part of the cell cycle to get ready for the next round of mitosis
What is the mitotic index?
The mitotic index is the proportion of cells undergoing mitosis in a sample of tissue.
How is the mitotic index calculated?
Mitoticindex=Numberofcel swithvisiblechromosomes /Totalnumberofcellsobserved
What does a high mitotic index indicate?
A high mitotic index means many cells are dividing, which suggests rapid tissue growth (e.g., in a plant root tip).
What is Found in Both Plant and Animal Cells
Nucleus – Both
Lysosome – Both (though more prominent in animal cells)
Ribosome – Both
Rough Endoplasmic Reticulum (RER) – Both
Smooth Endoplasmic Reticulum (SER) – Both
Golgi Apparatus – Both
Mitochondria – Both
What organelle is only found animal plants
Centriole – Animal cells only
core prac mitosis
docs
What are gametes?
Gametes are the male and female sex cells found in all organisms that reproduce sexually.
What happens when gametes join together?
They undergo fertilisation to form a zygote, which divides and develops into a new organism.
What are the male and female gametes in animals?
The male gametes are sperm, and the female gametes are egg cells (ova).
How many chromosomes do normal body cells contain?
Normal body cells contain the full number of chromosomes. Humans have 46 chromosomes—23 from the male parent and 23 from the female parent.
How many chromosomes do gametes contain?
Gametes contain half the number of chromosomes as body cells (23 in total for humans), making them haploid cells.
What is a zygote?
A zygote is formed when a sperm and an egg cell fuse during fertilisation. It has the full number of chromosomes.
Why does fertilisation lead to genetic variation?
Combining genetic material from two individuals makes offspring genetically unique.
What type of cells are egg cells and sperm cells?
They are eukaryotic cells, containing a nucleus and a cell membrane (plasma membrane). And other eukaryote organelles.But the structures of egg cells and sperm cells are also specialised for their function
What are the specialised and non specialised structures of an egg cell?
Follicle cells form a protective coating.
Zona pellucida is a protective glycoprotein layer needed for sperm to penetrate.
Large food reserves to nourish the developing embryo.
Nucleus and cell membrane
What are the specialised and non specialised structures of a sperm cell?
Lots of mitochondria provide energy for movement.(respiration happens here releases energy in form of ATP needed to swin)
Flagellum (tail) enables the sperm to swim towards the egg.
Acrosome contains digestive enzymes to break down the egg’s zona pellucida and enable penetration.
nucleus cell membrane
Where are sperm deposited in mammals?
Sperm are deposited high up in the female vagina, close to the entrance of the cervix.
How do sperm reach the oviduct?
Sperm swim through the cervix, uterus, and into one of the oviducts.
What happens when the sperm reach the oviduct?
Fertilisation may occur if an egg is present.
Female reproduction system label
x
What is fertilisation process made up of
Acrosome reaction and post acrosome reaction
fertilisation process acrosome reaction
The sperm swim towards the egg cell in the oviduct.
Once one sperm makes contact with the zona pellucida of the egg cell
the acrosome reaction occurs — this is where digestive enzymes are released from the acrosome
of the sperm.
These enzymes digest the zona pellucida, so that the sperm can
move through it to the cell membrane of the egg cell.
fertilisation process post acrosome reaction
The sperm head fuses with the cell membrane of the egg cell. This triggers the
cortical reaction — the egg cell releases the contents of vesicles called cortical
granules into the space between the cell membrane and the zona pellucida.
The chemicals from the cortical granules make the zona pellucida thicken, which makes it
impenetrable to other sperm. This makes sure that only one sperm fertilises the egg cell.
Only the sperm nucleus enters the egg cell — its tail is discarded.
The nucleus of the sperm fuses with the nucleus of the egg cell — this is fertilisation.
What is meiosis?
Meiosis is a type of cell division that happens in the reproductive organs to produce gametes.
How does meiosis affect chromosome number?
Cells that divide by meiosis have the full number of chromosomes to start with, but the cells formed from meiosis have half the number.
Why is meiosis important for reproduction?
Without meiosis, you’d get double the number of chromosomes when gametes fuse at fertilisation.
What are the key steps of meiosis?
The DNA replicates so there are two identical copies of each chromosome, called chromatids.
The DNA condenses to form double-armed chromosomes, made from two sister chromatids.
The chromosomes arrange themselves into homologous pairs — pairs of matching chromosomes (one from each set of 23 — e.g. both number 1s).
The homologous pairs are separated, halving the chromosome number.
The pairs of sister chromatids are separated.
Four new daughter cells that are genetically different from each other are produced. These are the gametes.
Why does meiosis produce genetic variation?
Meiosis produces gametes that are genetically different from each other.
How does crossing over create genetic variation?
Before the first division, homologous chromosome pairs line up.
Two chromatids in each pair twist around each other.
The twisted bits break and rejoin the opposite chromatid, recombining genetic material.
The chromatids still contain the same genes but have different combinations of alleles.
This means each new daughter cell has chromatids with different alleles.
What are linked genes?
The position of a gene on a chromosome is called a locus (plural: loci). Independent assortment means
that genes with loci on different chromosomes end up randomly distributed in the gametes.
But genes with loci on the same chromosome are said to be linked — because the genes are on the same chromosome,
they’ll stay together during independent assortment and their alleles will be passed on to the offspring together.
The only reason this won’t happen is if crossing over splits them up first.
The closer together the loci of two genes on a chromosome, the more closely they
are said to be linked. This is because crossing over is less likely to split them up.
What is independent assortment of chromosomes?
Four daughter cells from meiosis have completely different combinations of chromosomes.
Each cell receives a mix of chromosomes from both parents.
When gametes are produced, maternal and paternal chromosomes are distributed randomly.
This is called independent assortment.
What are sex-linked characteristics?
A characteristic is sex-linked when the locus of the allele coding for it is on a sex chromosome.
In mammals, females have XX chromosomes, males have XY.
The Y chromosome is smaller and carries fewer genes.
Males only have one X chromosome, meaning they often express recessive characteristics of genes on the X chromosome.
Genetic disorders caused by faulty alleles on sex chromosomes include color blindness and haemophilia.
What are multicellular organisms made from?
Many different cell types specialized for their function (e.g., liver cells, muscle cells, white blood cells).
Where do all specialized cells originate from?
Stem cells.
What are stem cells?
Undifferentiated cells that can develop into other types of cells.
What is differentiation?
The process by which a cell becomes specialized.
What is potency in stem cells?
The ability of stem cells to differentiate into specialized cells.
What are the two types of potency in stem cells?
Totipotency – The ability to produce all cell types, including specialized cells in an organism and extraembryonic cells (placenta, umbilical cord).
Pluripotency – The ability to produce all specialized cells in an organism but not extraembryonic cells.
When are totipotent stem cells present?
In mammals, during the first few divisions of an embryo.
What happens to stem cells after the totipotent stage?
They become pluripotent, meaning they can still specialize into any cell type in the body but not extraembryonic cells.
What are adult stem cells?
Multipotent stem cells found in mature tissues that replace specialized cells (e.g., intestinal epithelial cells).
How do stem cells in plants differ from animal stem cells?
They remain pluripotent throughout the plant’s life.
What happens to genes in stem cells during specialisation?
Some genes are activated while others are inactivated, leading to specialisation.
What is transcribed from active genes?
mRNA is transcribed only from active genes.
What is a cell’s genome?
A cell’s genome is its entire set of DNA, including all the genes it contains.
How do stem cells become specialised?
Stem cells become specialised because different genes are activated or inactivated under the right conditions.
Why don’t all genes in a cell’s genome get expressed?
A cell doesn’t express all the genes in its genome because not all of them are active.
How do proteins affect the cell?
Proteins modify the cell by determining its structure and controlling cell processes.
What happens to mRNA after transcription?
The mRNA from active genes is translated into proteins.
How do proteins influence further gene expression?
Proteins can activate more genes, leading to the production of even more proteins.
What causes a cell to become specialised?
Changes caused by proteins determine the cell’s structure and function, leading to specialisation.ºº
Can a specialised cell become unspecialised again?
No, once a cell has specialised, the changes are difficult to reverse, so it stays specialised.
How can gene expression be controlled?
Gene expression can be controlled by altering the rate of transcription of genes.
How does increased transcription affect protein production?
Increased transcription produces more mRNA, which leads to the production of more protein.
What controls the rate of gene transcription? what is is
Transcription factors — proteins that bind to DNA and activate or deactivate genes.
What are activators and repressors?
Activators increase the rate of transcription, while repressors decrease it.
How do activators work?
Activators help RNA polymerase bind to DNA, beginning transcription.
How do repressors work?
Repressors prevent RNA polymerase from binding, stopping transcription.
Where do transcription factors bind in eukaryotes?
They bind to specific DNA sites near the start of their target genes.
What do structural genes in an operon do?
They code for useful proteins, such as enzymes.
What is an operon?
A section of DNA containing structural genes, control elements, and sometimes a regulatory gene.
How is gene expression controlled in prokaryotes?
It often involves transcription factors binding to operons.
What are the control elements in an operon?
A promoter (where RNA polymerase binds) and an operator (where transcription factors bind).
What does a regulatory gene do?
It codes for an activator or repressor to control transcription.
What is the lac operon?
The lac operon is a section of DNA in E. coli that contains genes needed to produce enzymes for lactose metabolism.
When does E. coli use lactose for respiration?
E. coli respires glucose but can use lactose when glucose isn’t available.
What are the three structural genes in the lac operon?
lacZ, lacY, and lacA, which code for proteins like β-galactosidase and lactose permease.
What happens when lactose is NOT present?
The regulatory gene (lacI) produces the lac repressor,
which is a transcription factor that binds to the operator site when there’s no lactose present. This blocks transcription because RNA polymerase
can’t bind to the promoter.The regulatory gene (lacI) produces the lac repressor, which binds to the operator and blocks transcription.
How does the lac repressor block transcription?
It prevents RNA polymerase from binding to the promoter.
What happens when lactose is present?
When lactose is present, it binds to the
repressor, changing the repressor’s shape so that it can no longer bind to the operator site. RNA polymerase can now begin
transcription of the structural genes.
How does the presence of lactose enable transcription?
RNA polymerase can now bind to the promoter and transcribe lacZ, lacY, and lacA.
What is the function of the operator in the lac operon?
to regulate transcription by acting as a binding site for the lac repressor. When lactose is absent, the repressor binds to the operator, blocking RNA polymerase and preventing transcription of the structural genes. When lactose is present, it binds to the repressor, causing it to detach from the operator, allowing RNA polymerase to transcribe the genes needed to digest lactose.”
What are stem cells?
Stem cells are undifferentiated cells that can develop into any specialized cell type.
What is the function of the promoter in the lac operon?
to provide a binding site for RNA polymerase, allowing transcription of the structural genes to begin.
Why are scientists interested in stem cells?
Scientists believe stem cells can be used to replace damaged tissues and treat diseases.
How are stem cells used in treating leukemia?
Leukemia treatments destroy bone marrow stem cells, so bone marrow transplants replace them.
How could stem cells help with spinal cord injuries?
Stem cells could be used to repair damaged nerve tissue in the spinal cord.
What is a major benefit of using stem cells in organ transplants?
They could be used to grow organs, saving lives of people waiting for transplants.
How could stem cells help with heart disease?
They could replace damaged heart tissue caused by heart disease or heart attacks.
How could stem cells improve the quality of life for blind people?
Stem cells could replace damaged cells in the eyes, potentially restoring vision.
What are the two main sources of human stem cells?
Adult stem cells – Found in specific tissues like bone marrow, can develop into a limited range of cells.
Embryonic stem cells – Can develop into any type of specialised cell.
Adult stem cells, and how are they obtained?
These are obtained from the body tissues of an adult.
For example, adult stem cells are found in
bone marrow.
They can be obtained in a relatively simple operation
with very little risk involved, but quite a lot of
discomfort. The donor is anaesthetised, a needle is
inserted into the centre of a bone (usually the hip)
and a small quantity of bone marrow is removed.
What are the advantages and limitations of adult stem cells?
Adult stem cells aren’t as flexible as embryonic stem
cells — they can only develop into a limited range
of cells.
However, if a patient needs a stem cell transplant
and their own adult stem cells can be used (from
elsewhere in their body) there’s less risk of rejection.
Where are embryonic stem cells obtained from?
Embryonic stem cells are obtained from early embryos created in a laboratory using in vitro fertilisation (IVF). The embryo is about 4-5 days old when the stem cells are removed.
Why are embryonic stem cells considered more versatile than adult stem cells?
Embryonic stem cells can develop into any type of specialised cell, while adult stem cells can only develop into a limited range of cells.
Disadvanatges of embryonic stem cells
Rejection of transplants occurs quite often and is
caused by the patient’s immune system recognising
the cells as foreign and attacking them
What ethical issues are associated with using embryonic stem cells?
Using embryos created through IVF for stem cell research raises ethical concerns because it involves the destruction of a viable embryo, which some believe has the potential to become a fetus.
Why do some people believe it is wrong to destroy embryos for stem cell research?
Many people believe that at the moment of fertilisation, a genetically unique individual is formed and has the right to life. Therefore, they argue that destroying embryos is ethically wrong.
Why do some people have fewer objections to using embryonic stem cells?
Some people believe it is acceptable to use embryos created through IVF for stem cell research because these embryos would not have been implanted in a womb and allowed to develop into a fetus.
Why do some people argue that only adult stem cells should be used?
Some people prefer the use of adult stem cells because their extraction does not involve the destruction of an embryo. However, adult stem cells cannot develop into all specialised cell types like embryonic stem cells can.
Why are regulatory authorities needed for embryonic stem cell research?
Regulatory authorities help society make informed decisions about embryonic stem cell research by considering both benefits and ethical concerns. They ensure that research involving embryos is conducted for valid reasons and follows ethical guidelines.
Why is decision-making about stem cell research complicated?
Decision-makers must consider the views of all people in society when making choices about stem cell research and its use in medicine. Ethical concerns about destroying embryos need to be balanced with the potential benefits of treatment.
What is the role of regulatory authorities in embryonic stem cell research?
Looking at proposals of research and deciding if they should be allowed,
taking the ethical issues surrounding the work into account — this ensures
that any research involving embryos is carried out for a good reason.
This also makes sure research isn’t unnecessarily repeated by different groups. authority, you’ll need
to consider all the
benefits and issues
of stem cell research
when asked
2) Licensing and monitoring centres involved in embryonic stem cell research — this ensures that only
fully trained staff carry out the research. These staff will understand the implications of the research
and won’t waste precious resources, such as embryos. This also helps to avoid unregulated research.
3) Producing guidelines and codes of practice — this ensures all scientists are working
in a similar manner (if scientists don’t use similar methods their results can’t be
compared). It also ensures that the scientists are using an acceptable source of stem
cells and that the methods they use to extract the cells are controlled. This includes
regulating the maximum age of an embryo that can be used as a source of stem cells.
4) Monitoring developments in scientific research and advances — this
ensures that any changes in the field are regulated appropriately and that
all the guidelines are up to date with the latest in scientific understanding.
5) Providing information and advice to governments and professionals — this helps to promote the science
involved in embryo research, and it helps society to understand what’s involved and why it’s important.
What is phenotype?
Phenotype is the set of observable characteristics displayed by an organism, influenced by both its genotype and environment.
What is discontinuous variation?
Discontinuous variation is when individuals fall into distinct categories with no intermediates (e.g., blood groups: A, B, AB, O).
What is continuous variation in phenotype?p
Continuous variation is when individuals in a population show a range of characteristics without distinct categories (e.g., height, mass, skin color).
How does a graph of discontinuous variation appear?
As distinct separate bars (not a continuous curve).
What is a monogenic characteristic?
A characteristic controlled by only one gene. These usually show discontinuous variation (e.g., blood groups).
How does variation in genotype influence phenotype?
Different genotypes result in different phenotypes because genes determine the characteristics an organism displays
What are polygenic characteristics?
Characteristics controlled by multiple genes at different loci, which usually show continuous variation (e.g., height, skin color).
What is the locus of a gene?
The specific position of a gene on a chromosome where different alleles of the same gene are found.
What are the two sources of human stem cells?
Adult stem cells – Found in body tissues like bone marrow, can only develop into a limited range of cells.
Embryonic stem cells – Obtained from early embryos, can develop into any type of specialised cell.
What are the advantages of using adult stem cells in treatment?
Lower risk of rejection if taken from the same person.
Fewer ethical concerns as they don’t require destroying an embryo.
Can be obtained through a relatively simple operation with little risk involved.
Why are embryonic stem cells useful in medicine?
Can develop into any type of specialized cell.
Could potentially be used to replace damaged tissues in diseases.
May save lives, e.g., by replacing cells in organ failure or treating blindness.
What are some existing medical uses of stem cell therapy?
Leukaemia treatment – Stem cells can replace damaged bone marrow.
Heart disease and heart attack damage – Stem cells could help replace damaged heart tissue.
Treating blindness by repairing damaged eye cells.
What are the main ethical concerns about embryonic stem cell research?
Destruction of embryos that could develop into fetuses.
Some argue that only adult stem cells should be used, as they don’t destroy embryos.
Using artificially activated egg cells (not fertilized by sperm) may reduce ethical concerns, as they can’t develop into a fetus.
How does society regulate embryonic stem cell research?
Consider ethical concerns and allow research only if it has a good reason.
Avoid unnecessary repetition by different research groups.
License and monitor research centers to ensure work is done by trained professionals.
Prevent misuse of embryos and ensure their use is ethical.
Update regulations based on new scientific developments.
Are all characteristics influenced by both genotype and environment?
No. Some characteristics are influenced only by genotype (e.g., blood group), but most characteristics result from both genotype and environmental factors (e.g., weight).
How do genetics and the environment influence height?
Height is polygenic (controlled by multiple genes).
Nutrition plays a major role, especially protein intake.
Tall parents usually have tall children, but undernourishment prevents them from reaching their full potential height.
What is Monoamine Oxidase A (MAOA), and how is it influenced by genotype and environment?
MAOA is an enzyme that breaks down monoamines (a type of chemical).
Low levels of MAOA have been linked to mental health problems.
MAOA production is controlled by a single gene (it’s monogenic).
Environmental factors, such as anti-depressants or tobacco use, can reduce MAOA production.
How do genetics and environmental factors contribute to cancer?
Cancer is uncontrolled cell division that leads to tumour formation.
The risk of some cancers is influenced by genes.
Environmental factors like diet, smoking, and UV exposure also play a role in increasing cancer risk.
How does the environment influence hair color in some animals?
Animal hair color is polygenic (controlled by multiple genes).
Some arctic animals change fur color based on temperature (e.g., dark fur in summer, white fur in winter).
The environmental trigger (temperature drop) causes the change, but the animal must have the genes for this ability.
What is epigenetic control, and how does it influence gene expression?
Epigenetic control determines whether certain genes are expressed or silenced, altering the phenotype.
It does not change the base sequence of DNA.
Instead, it works by adding or removing chemical groups to DNA, affecting how easily transcription enzymes can bind to genes.
Can environmental changes affect gene expression?
Epigenetic changes can occur in response to the environment, such as:
Pollution
Availability of food
These changes affect how genes are expressed without altering the DNA sequence itself.
What is DNA methylation, and how does it affect gene expression?
Methylation is an epigenetic modification where a methyl group is attached to the DNA coding for a gene.
This happens at CpG sites (where cytosine and guanine are next to each other).
Increased methylation changes the DNA structure, making it difficult for transcription enzymes to bind.
As a result, the gene is repressed (silenced) and not expressed.
What are histones, and what role do they play in gene expression?
Histones are proteins that DNA wraps around to form chromatin, which makes up chromosomes.
Chromatin can be highly condensed or less condensed, affecting whether transcription proteins can bind to DNA.
How do epigenetic modifications to histones influence gene expression?
Epigenetic modifications include the addition or removal of acetyl groups from histones.
These modifications affect how tightly or loosely the chromatin is packed, influencing gene transcription.
What happens to gene expression when histones are acetylated?
Acetylation of histones makes chromatin less condensed.
This allows transcription proteins to bind to DNA, enabling genes to be transcribed (activated).
What happens to gene expression when acetyl groups are removed from histones?
When acetyl groups are removed, chromatin becomes highly condensed.
Genes in the DNA can’t be transcribed because transcription proteins can’t bind to them.
This leads to gene repression (silencing).
Can epigenetic changes be passed on after cell division?
Yes When a cell divides and replicates, epigenetic changes may be passed on to daughter cells.
How do epigenetic changes get inherited during cell division?
Methyl groups are usually removed from DNA during gamete formation, but some escape the removal process and end up in sperm or egg cells.
If these changes are passed on, genes activated or deactivated in the original cell will also be activated or deactivated in daughter cells.
What happens if an epigenetic change occurs due to an environmental change?
If an epigenetic change happens in response to an environmental factor, it means the daughter cells will be equipped to respond to the same environment in the same way as the original cell.
How are red blood cells specialized for their function in oxygen transport?
Red blood cells are specialized for oxygen transport by containing lots of haemoglobin and having no nucleus, allowing more space for haemoglobin. They are produced from stem cells in the bone marrow, where genes for haemoglobin production are activated. Other genes, such as those involved in removing the nucleus, are also activated, resulting in a fully specialized red blood cell capable of efficiently carrying oxygen.
