mitosis and stem cells, reproduction and meiosis, non communicable diseases Flashcards
what does the nucleus of a cell contain?
- chromosomes
What are chromosomes made out of?
DNA molecules
What does a chromosome carry?
- many genes
What are genes?
a small section of DNA on a chromosome
What do genes do?
- carry instructions for making proteins
- determine characteristics of living things
how are chromosomes usually found?
- in pairs
- each chromosome in pair is usually of similar size and shape
- genes at the same location of each of matching chromosomes code for similar things
How many chromosomes do humans have?
23 pairs
different species have different numbers of chromosomes
what would chromomes look like in a cell that is not dividing?
- not be clearly visible
- made of only 1 DNA molecule
What are the three stages of the cell cycle?
1) cell growth- number of subcellular structures increase + DNA replicates to form 2 identical copies of each chromosome
2) mitosis- chromosomes separate then the nucleus divides in two
3) cell division- to make 2 identical daughter cells cytoplasm and cell membrane divides
What are the stages of mitosis?
1) newly replicated chromosomes are joined together
2) they move to the centre of the cell
3) chromosomes are pulled apart and move to opposite poles of the cell
4) the nucleus divides, each new nucleus contains one full set of chromosomes
What do you call cells that are divided by mitosis?
- genetically identical
What is mitosis used for?
- growth of multi cellular organisms
- repair and replacement of cells
What are cells in an early embryo?
- unspecialised
- can differentiate into most different types of human cells
What do scientists do to embryonic stem cells?
clone cells
(making genetically identical copies of cells)
What is the difference between adult stem cells and embryonic stem cells in terms of function?
- stem cells in adults can only produce a limited range of cell types
- replace cells that are worn out or damaged
- differentiate to produce few cell types
What are meristems?
specialised tissues in a plant that contains stem cells
What can cells produced by plant meristems do?
- differentiate into any type of plant cell throughout the life of a plant
Where can meristems be found?
in the growing tips of roots and shoots
How are stem cells used for medical treatment?
- replaces faulty or damaged cells
What is the cultivation process for stem cells?
therapeutic cloning
- collect cell from patient and donated egg cell
- egg cell nucleus replaced by nucleus from patient’s cell
- embryo made that has same genes as patient (therapeutic cloning)
- stem cells removed and used to treat patient
What are the advantages of therapeutic cloning?
- may treat diseases and replace faulty organs
- produces wider range of cells than possible than collecting adult stem cells
- not rejected by patient’s immune system
- many cells produced, some could be used in research
What are the disadvantages of therapeutic cloning?
- stem cells may transfer viral infection
- ethical issues- some people may think that embryo is still a life
- human egg cells are in short supply, collecting them has risks
- may have side effects that are not known while using stem cells
How are plant stem cells used in the laboratory?
- meristem cells cut from a plant
- cultured in laboratory
- produces identical new plants
- new plants are clones of parent plant
What are the advantages of growing plants from stem cells?
- large numbers of new plants produced cheaply and quickly
- rare species could be cloned to prevent exinction
- useful features in crop plants can be cloned from mertistem tissues = many identical useful plants for farmers
What is therapeutic cloning?
- therapeutic cloning produces stem cells from cloned embryos
- stem cells not rejected by patient’s body because they have the same genes as patient
how do you define health?
- the state of a person’s physical and mental well-being
What is a non-communicable disease?
diseases that cannot be passed onto other people
Give an example of how diseases can interact
- HPV virus as been linked to cervical cancer
- viruses living in cells could tigger cancers
What is epidemiology?
- study of patterns of disease in populations
What conditions should a sample include?
- avoid bias
- cover all types of people found in the population
- representative of the population
- random sampling is used to achieve this
larger samples are more likely to be representative
Why is sampling used?
- studying the entire population would be too time consuming and difficult
What are lifestyle factors?
- aspects of the way people live their lives
- eg. diet, exercise, smoking, alcohol intake
What is the disease that obesity is the main risk factor for?
type 2 diabetes
- cells become less responsive to insulin
- blood sugar levels are not controlled = diabetes
What is the disease that alcohol intake is the main risk factor for?
- poor liver and brain function
- long term alcohol use = cirrhosis (pernament damage) to the liver
- causes memory loss and pernament brain damage
What is the disease that diet is the main risk factor for?
- cardiovascular disease
- diet rich in high energy foods and saturated fat + lack of exercise
- build up of plaque in blood vessels
- high blood pressure
- smoking damages arteries + cause high blood pressure
What does smoking and alcohol intake during pregnancy cause?
- affects health of unnorn babies
- smoking = premature birth, low birthweight
- excessive alchol = abnormal facial features and problems with brain and nervous system
What is a risk factor in disease?
any aspect linked to an increased rate of a disease
How do substances in cigarrete smoke damage the lungs and other places in the body?
- carried in the bloodstream
- causes damage to cells
- triggering cancer elsewhere in the body
How is lung cancer caused by smoking?
- caused by carcinogens in cigarette smoke
How are other forms of lung disease caused by smoking?
- toxins in cigarette smoke cause damage in walls of airways and alveoli
- reduced oxygen exchange -> shortness of breath
How are genetics a risk factor?
- inherited mutations of some genes are associated with higher risk of some cancers
- can be tested
How do carcinogens cause cancer?
- damage DNA in cells
- causes mutations that can lead to cancer
What is a carcinogen?
- a chemical or physical agent that can cause the development of cancer in cells
- eg asbestos, types of ionising radiation (UV light)
What is cancer caused by?
- uncontrolled division of cells
What is a tumour?
- a growth that is caused by cancer cells
What do malignant tumours do?
- detach from tumour and invade neighbouring tissues
- (metastasis)
- squeeze through capillary walls and move into blood stream
- carries them to different parts of body
- enter other tissues and divide to form secondary tumours
What are benign tumours?
- growths of abnormal cells that do not invade other parts of the body
- tumour contained in one area
- usually surrounded by membrane
How can benign tumours cause problems?
- putting pressure on important body structures
lower health risks than malignant tumours
What are gametes?
- specialised cells produced for sexual reproduction from animals and plants
How are gametes created?
- meiosis
Are cells created by meiosis genetically identical to each other?
no
What are the two types of gametes created by plants?
- pollen cells (moved from one parent plant to another by wind/ animals)
- egg cells
What is asexual reproduction?
- when a single organism reproduces
- offspring are all genetically identical to each other
- offspring reffered to as “clones”
How is asexual reproduction performed?
- small parts of an organism separating from parent to form new individual
- made by mitosis
What happens during meiosis?
- copies DNA
- chromosomes doubled
- cell divides twice
- ends up with four genetically different cells
Why does meiosis result in four genetically different cells?
- doubled number of chromosomes has been halved twice
- each of four cells end up with half of normal number of chromosomes
Describe the process of fertilisation
- gametes have 23 chromosomes
- sperm cell fuses with egg cell two sets of 23 chromosomes are mixed together
- forms zygote
- divides many times by mitosis to form embryo
What are the advantages of asexual reproduction?
- faster than sexual reproduction, one parent needed (less time spent finding mate)
- in favorable conditions large number of identical individuals can be rapidly produced
What is an disadvantage of asexual reproduction?
- less favourable conditions = all individuals are badly affected due to no variation
- single disease could wipe out entire population of genetically identical individuals
What are advantages of sexual reproduction?
- variation in offspring = some are possible to survive changing conditions (natural selection)
- in plants they produce seeds which allow them to be dispersed to new areas
What are the disadvantages of sexual reproduction?
- takes longer (gametes have to find each other)
- finding a mate requires energy
How do malarial parasites reproduce?
- reproduces asexually when inside human host
- large number of parasites in blood = larger chance of mosquito biting human to be infected
- reproduces sexually when inside mosquitoes
- variation in parasites that are passed onto humans
How do fungi reproduce?
- spores produced asexually
- spores spread on air currents to new places to increase chances of fungus growing on new food source
- two fungi of same species grow next to each other = sexual reproduction = variation
How do strawberries and daffodils reproduce?
- produce flowers and reproduce sexually once a year
- daffodils bud off smaller bulbs
- strawberry plants grow young plants on runners
- produces offspring quickly to colonise local area
Name five factors that can affect health
- diet
- exercise level
- life situations
- stress
- diseases
