Mutations Stem Cells Genome Projects Gene Technology Flashcards
(Refer to June 2011 paper) Plant physiologists attempted to produce papaya plants using tissue culture. They investigated the effects of different concentrations of two plant growth factors on small pieces of the stem tip from a papaya plant. Their results are shown in the table.
Callus is a mass of undifferentiated plant cells. Plantlets are small plants.
Explain the evidence from the table that cells from the stem tip are totipotent. (2)
Gives rise to new plants;
So must be able to develop into different tissues
Calculate the ratio of cytokinin : auxin that you would recommend to grow papaya plants by this method
5:1
Papaya plants reproduce sexually by means of seeds
Papaya plants grown from seeds r very variable in their yield
explain why
Crossing over during meiosis and the random fertilisation of gametes
Explain the advantage of growing papaya plants from tissue culture rather than from Seeds
They will b genetically identical
Totipotent
Can differentiate into any type of body cell
Pluripotent cells found in ..
Can differentiate into …
Embryos and can differentiate into almost any type of cell
Multi-potent and unipotent
Found in mature mammals
Multipotent = differentiate into a limited number of cells e.g. bone marrow - wbc , rbc,
Unipotent - can only differentiate into one type of cell , cardiomyocytes
Ips cells
Created from adult unipotent cells
Treated w transcription factors to switch on genes that induce pluripotency
Advantages : don’t cause embryonic destruction Self renewal (can divide indefinitely to give a limited supply) Used in medical treatment instead of embryonic cells
Multipotent cells are found in …
Multipotent cells are found in mature mammals
Totipotent cells can develop into
Totipotent cells can develop into pluripotent cells in embryos
Totipotent cells exist for..
Totipotent cells exist for limited time in embryonic development
Pluripotent cells can b used to
Treat human disorders
Stages of regulation by oestrogen
Oestrogen enters the cell thru the phospholipid bilayer
Oestrogen binds to receptors on transcription factors in the cytoplasm
Binding of oestrogen causes the transcription factors to change shape and form a receptor-hormone complex
The receptor-hormone complex enters the nucleus
The receptor-hormone complex binds to the promotor region of the dna
Transcription is initiated
What is a mutation
A change to the base sequence of DNA
describe what happens In a translocation mutation
A sequence of bases is moved from one location in the genome to another
Explain why a mutation in a polypeptide that makes of an enzyme could affect the enzymes function
The mutation may result in a change to the shape of the enzymes active site
this may stop substrates from being able to bind to the active site
leaving the enzyme unable to catalyse the reaction
What is a hereditary mutation
Mutation thats Passed on to an individual’s offspring as a result of a mutation in the gametes
Do Mutations always affect the protein coded for by the gene explain your answer
No because the genetic code is degenerate this means that not all mutations will result in a change to the amino acid sequence of a protein
2-aminopurine is a base analog That can substitute for both adenine and guanine during DNA replication
explain why this base is a mutagenic agent
This base can pair with both thymine and cytosine which could cause a substitution mutation in the new DNA during DNA replication
Mustard gas is an alkylating agent Explain how exposure to mustard gas may affect the sequence if amino acids in a particular polypeptide
Alkylating agents such as mustard gas can add an alkyl group to guanine, changing the structure so that it pairs w thymine instead of c which may result in a change in the amino acid sequence of a polypeptide
When might a mutation occur spontaneously
During dna replication
Whats a mutagenic Agent
sumn that causes an increase in the number of mutations
Mutagenic agents examples
Ionising radiation
Uv radiation
Base analogs
Alkylating agents
P53 is a tumour suppressor gene mutations in P53 are found in over half of all cancers
suggest how p53 normally functions
suggest how mutations in P53 could lead to cancer
A mutation in p53 could inactive the gene
the protein it codes for wont be produced
this will cause cells to start dividing uncontrollably eventually leading to cancer
A woman has found a lump in her breast
her doctor tells her that she has breast cancer and left it spread to her liver the woman is 49 years old and is having oestrogen-containing HRT to treat symptoms of the menopause
explain why taking HRT may have contributed to the woman developing breast cancer
HRT increases oestrogenic levels in the body
An increase in exposure to oestrogen over an extended period of time is thought to increase the risk of developing breast cancer