paper 1: All Cells Arise from Other Cells Flashcards
what is a chromosome
one DNA molecule folded into a condensed form, wrapped around histone proteins in eukaryotes
after DNa replication what is a chromosome made of
2 genetically identical sister chromatids
show a chromosome before and after DNA replication
how are chromosome homologous pairs
one chromosome is inherited from the mother and one chromosome is inherited from a father
what is the definition of a homologous chromosome
the same genes but potentially different alleles
define a gene
a section of DNA that codes for a polypeptide or functional RNA
define an allele
different forms of the same gene that code for a specific trait
what is a chromosome number
the number of chromsomes possessed by an organism (n)
define a diploid cell
diploid cells have a homologous pairs of chromosomes
what is a haploid cell
haploid cells have one copy of each homologous chromosome
what are the main stages of the cell cycle
interphase prophase metaphase anaphase telophase cytokinesis
define mitosis
cell division that produces 2 genetically identical daughter cells from a parent cell
why do cells need to carry out mitosis
growth and repair tissues & replace cells
what happens during interphase
- new proteins are synthesised
- DNA replicates
- new organelles are made
when are chromosome visible
in the stages of mitosis
what happens during prophase
- chromosomes condense and become visible
- nuclear membrane breaks down centrioles move to opposite poles of the cell
- spindle fibres form
what happens during metaphase
- spindle fibres attach to centromere
- chromosomes are lined up at the equator of the cell
what happens during anaphase
- spindle fibres contract splitting the centromere
- v-shaped sister chromatids are separated and pulled apart to opposite poles of the cell
what happens during telophase
- spindle fibres break down
- a new nuclear membrane forms around each group of chromosomes
- chromosomes uncondense
what happens during cytokinesis
the cytoplasm divides into 2 to create 2 separate daughter cells
how does cancer forms
- if a mutation occurs in one of the control genes, then cell division continues
- uncontrolled cell division can lead to the formation of tumours and cancers
- mutation occurs at random
- mutagenic agents increase the chances if mutation
what are some examples of mutagenic agents
- UV radiation, ionising radiation, carcinogens (cigarettes, asbestos)
what are the 2 types of tumour
benign and melignant
what are benign tumours
slow growing tumours that don’t spread to the rest of the body
what are melignant tumours
fast growing tumours that cells break off of and spread to other parts of the body
what is the difference between a tumour and a cancer
a tumour is a mass of cells dividing uncontrollably, if those cells break off and spread it becomes a cancer
how do cancer treatments control the rate of cell division
- prevents the synthesis of enzymes needed for cell replication
- damage DNA
- prevent the formation of spindle fibres
what is a negative of cancer treatments
the treatments cannot distinguish between healthy and cancerous cells so they destroy normal body cells that are dividing
how do prokaryotic cells replicate
a process called binary fission
- the circular DNA and the plasmids replicate
- the copies of circular DNA move to separate poles of the cell
- the cytoplasm divides to produce 2 daughter cells
- each cell contains a single copy of the circular DNA but a variable number of plasmids
how do viruses replicate
- they use a specific host cell to replicate
- the virus attachment protein binds to a specific complimentary receptor protein on a specific host cell
- the viral DNA/RNA is injected into the host cell
- the host cell uses the viral genetic material and its own ribosomes and enzymes to synthesise viral proteins
- the viral particles are formed and release from the host cell
