Division and differentiation in human cells Flashcards
Somatic cell
any cell in body other than cells involved in reproduction
how do somatic cells divide
mitosis
Germline cell
Gametes and the stem cells that divide to form gametes
How do germline cells divide
Mitosis to produce more germline cells to maintain diploid chromosome number 23 pairs homologous chromosomes
or
Meiosis to produce haploid gametes - haploid 23 single chromosomes
Fertilisation
Created by fusion of 2 nuclei of gametes to form zygote
In meiosis
copies of genetic information made
cell divides twice to form 4 gametes, each with single set of chromosomes
all gametes are genetically different from each other, they show variation
differentiated
cells express specific genes that characterise a certain type of cell
only produces the proteins characteristic for that type f=of cells
Stem cells
continuously undergo cell division
embryonic stem cells
tissue (adult) stem cells
Embryonic stem cells
early embryo
able to divide continuously
pluripotent - all genes can be expressed and can become all cells - important for growth
Tissue adult stem cells
Found in mature organism
Function is to replenish all differentiated cells found in that specific tissue
multipotent - any type of cell of same tissue type
Stem cells therapeutic uses
skin graft for burn victims
repair cornea - limbal cells
Medical uses of stem cells
Treating patients with untreatable conditions
Growing organs for transplants
Medical research
clinical issues with stem cells
no guarantee of success
difficult to find suitable stem cell donors
difficult to obtain patients embryonic stem cells
mutations have been observed
cultured stem cells can be contaminated by viruses
Ethical issues with stem cell research
embryonic stem cell is unused embryos produced by in vitro fertilisation
for therapeutic cloning - is it right to create embryo for therapy and destroy them in process
could develop into person
at what stage is considered a person?
Social issues with stem cell research?
Educating public
do benefits outweigh objections
patients could be exploited - paying a lot when stem cell research is only in early developmental stages
Cancer
cells grow and divide my mitosis when it grows and divides uncontrollably due to not responding to regulatory signals this is cancer
group of cancerous cells
tumour
2 types of tumours
benign or malignant
benign
grow slowly
usually grow within a membrane, so can easily be removed
do not invade other parts of body
malignant
grow quickly
invade neighbouring tissues and can spread through bloodstream
As grows, cancel cells may fail to attach to each other spreading through body where may form secondary tumour. This process is called metastasis
Metastasis
Secondary tumour
Cancer cell are called
undifferentiated - do not carry out normal function
what causes cancer?
Chemicals and other agents
genetic factors
lifesyle factors
lifestyle factors that can cause cancer
viruses such as HPV, being spread though sexual intercourse
carcinogens in cigarettes
alcohol intake
ultraviolet radiation
diet, including fat and salt intake
industrial and environmental factors at work that can lead to cancer?
exposure to ionising radiation
exposure to chemical carcinogens
what cells can lose ability to continuously replicate themselves
differentiated cells
