DNA and chromosomes Flashcards
State the 4 parts of the cell cycle
- G1 phase
- S phase
- G2 phase
- M phase
What happens during the M phase
- mitosis (nuclear division)
- cytokinesis (cytoplasmic divison)
Which phases does mitosis include?
- prophase
- metaphase
- anaphase
- telophase
What happens during the S phase of the cell cycle?
DNA replication
What happens during prophase?
- chromosomes condense
- mitotic spindles form
What happens during prometaphase?
- nuclear membrane disintegrates
- spindles attach to kinetochores
What happens during metaphase?
chromosomes align at equator
What happens during anaphase?
- sister chromatids seperate
- pulled towards spindle poles
What happens during telophase?
- chromosomes arrive at poles
- nuclear envelopes reform
What happens during cytokinesis?
cytoplasm divides resulting in two genetically identical cells
What do chemotherapy drugs target?
the S and M phases of the cell cycle, which rapidly kills replicating cells
Which direction is DNA synthesised in?
5’ to 3’ end
How is he accumulation of mutations prevented ?
- proof reading capacity of DNA polymerase during DNA replication
- excision repair systems act throughout cell life repairing DNA damage
How do you characterise mutations?
- impact on individual or offspring (somatic or germ line)
- scale of mutation
(chromosome or SNP) - effect on normal function
Describe what an SNP is?
- single nucleotide polymorphism
- single base chnage in DNA sequence
- no change in amino acid sequence
What are monogenic genetic diseases?
- single gene disorders
Give the 3 kind of monogenic genetic diseases and examples
- substitution (sickle cell anaemia)
- deletion (cystic fibrosis)
- insertion (huntington’s disease)
Describe sickle cell anaemia
- single nucleotide substitution in HBB gene (beta chain of haemoglobin)
- misshapen blood cells do not survive as long and clog capillaries
Describe cystic fibrosis
- abnormal mucus un lungs
- results in lung infections, difficulty breathing, digesting food
- impaired chloride transport (loss of function)
Describe Huntington’s disease
- neurodegenrative disease
- uncontrollable muscle movements
- loss of memory and depression
- difficulties with speech and swallowing
- damage of nerve cells in areas on the brain
What is the cause of Huntington’s disease ?
- caused by increase in number of CAG trinucleotide repeats (encoding glutamine) in the Huntingtin (HTT gene)
- polyglutamine residues stick together creating a toxic product which causes neuron cell death
What is the cause of cystic fibrosis?
70% have 3bp deletion in CFTR gene on chr 7 (cystic fibrosis transmembrane conductance regulator)
What controls the cell cycle checkpoints and how?
- cyclins
- protein kinases (cdks)
- phosphorylation of cdk/cyclin complexes
List the steps of DNA replication for the leading strand
- DNA helicase
- DNA primase
- DNA polymerase
List the steps of DNA replication for the lagging strand
- DNA primase
- DNA polymerase
- DNA nuclease
- DNA polymerase
- DNA ligase
Describe Werners syndrome
- premature aging disorder
- mutation in DNA helicase
- increased risk of cataracts, atherosclerosis, osteoporosis and cancer
What is xeroderma pigmentosum?
- autosomal recessive disorder
- mutation in UV repair
- unable to remove thymine dimers
What are some symptoms of xeroderma pigmentosum?
- acute sun sensitivity
- hypo/hyper pigmentation
- multiple cancers at a young age
- intellectual disability
- progressive degradation
Is cystic fibrosis a loss or gain of function?
loss of function
Is sickle cell anaemia a loss or gain of function?
loss of function
Is Huntington’s disease a loss or gain of function?
gain of function
