cell cycle , cellular ageing , cell death and gene expression Flashcards
what is a gene ?
A functional region of DNA which codes for a sequence of RNA
what is an allele ?
An individual variant of a gene
What is an exon ?
Portions of a gene product which are removed via splicing of RNA
what is an intron?
Portions of a gene product which are retained following splicing
what is the genotype?
The genes (and alleles of them) in a cell/organism
what is the phenotype?
The physical features of an organism resulting from its genotype
what is a mutation ?
Changes in the genetic sequence
how is RNA produced from DNA?
Transcription
what are the forms of RNA?
messanger RNA
transfer RNA [tRNA]
ribosomal RNA [rRNA]
short interferring and micro RNA [siRNA and miRNA]
what is a substitution mutation ?
one base is replaced with another
What are the 3 types of substitution mutations ?
Silent: New code is for same amino acid
Missense: The new code changes an amino acid
Nonsense: The new code is a STOP codon and stops the protein being produced
What does the frameshift mutation do?
Frameshift: The triplet code is disrupted, so all amino acids after the mutation
change
what are the types of frameshift mutations ?
Addition: A new base is added, shifting the rest forwards
Deletion: A base is removed, pulling the rest backwards
Mutations
what is a germline mutation ?
cells that will give rise to gametes
have genes that can be passed on
can be passed down through families
what is a somatic mutation ?
mutation does effect other cells only the ones it divides into
cannot be passed
what is proliferation ?
growth
replace dead / injured cells
happens in mitosis
when is proliferation vital?
plays a key role from embryogensis to whole organism
crititical in the maintenance of adult tissue homeostasis
why do some cells divide at specific times ?
enviroment = nutrience , temp , ph , oxygen
interactions with other cells and signalling molecules
intracellular signalling
what are the four stages of dividing cells ?
G1
S phase
G2
M phase
also G0 - for resting cells
what happens in G1 ?
preparation for DNA synthesis [ s phase]
what happens in G2 ?
preparation for cell division [ m phase ]
If DNA damage is detected, the cell will not be able to proceed through the cell cycle until that damage is repaired. If it can not be repaired, what process will occcur ?
apoptosis
What happens during s phase ?
DNA replication occur
DNA helicase breaks hydrogen bonds between DNA strand separating them
DNA polymerase catalyses addition polymerisation of DNA nucleotides
New nucleotides are added to the 3’ (“3 prime”)
end of the new strand. New nucleotides are
attached via their 5’ (“5 prime”) end
how is cell cycle controlled ?
fixed amount of time for each event
information from cell cycle event and external environment
what is s-phases ?
chromosomes undergo replication
new DNA is synthesised - duplicate chromosome constructed
chromosome only visible during division
after replication :
* Each chromosome is composed of two identical chromatids
- Chromatids are joined together at the centromere
what is m-phase ?
how cells physically divide to produce two genetically identical daughter cells
how many stages of mitosis are there and what are their names ?
5
prophase
prometaphase
metaphase
anaphase
telophase
what is cytokinesis ?
cytoplasmic division divides cells in two
what is prophase ?
chromosome condense and are visible and threadlike
nuclear membrane and nucleoli disappear
mitotic spindles begins to form
centrosomes move away from each other
what is prometaphase ?
nuclear envelope fragments
microtubules attach to the chromatids at the kinetochores
other microtubules interact connecting from different poles
what is metaphase ?
centrosomes are now at opposite poles
chromosomes are lined up on the metaphase plate
all chromosome are attached to each of the poles
what is anaphase ?
connection between chromatids at the centromere is cleaved
each chromatid is now a daughter chromosome
chromosome are pulled to opposite poles as cell elongates
anaphase ends when chromosome reaches poles
what is telophase ?
two daughter nuclei form
chromosomes become less dense
Contractile ring begins to assemble
* Actin and myosin filaments
* Cytoplasm is divided in two
* Creates two daughter cells, each with one nucleus
mitosis is complete
what is meiosis necessary for ?
production and function of gametes
why does meiosis cause a source of variation ?
- Fusion with different gamete for mixing of gene combinations
- Each gamete having a different combination of the parent’s genes
- Recombination resulting in new chromosomes
what are the principles of meiosis ?
Meiosis I: Homologous (paired) chromosomes are separated from one another but remain intact (sister chromatids still attached to one another).
Meiosis II: Sister chromatids on each
chromosome are separated into the new cells
what is the name of controlled cell death ?
Apoptosis
what is the name of uncontrolled cell death ?
necrosis
