topic 8 Flashcards
Explain how a single base
substitution causes a change in
the structure of a polypeptide.
- Change in (sequence of) amino acid(s)/primary structure;
Reject amino acids are formed.
Reject amino acids code. - Change in hydrogen/ionic/disulfide bonds;
- Alters tertiary/3 0 structure;
What is a substitution
mutation?
Replacement of a base by a different base (in DNA);
Suggest ways that putting ESCs
into a person’s heart might lead to more harm to the person.
- Might divide out of control;
- Leading to tumour / cancer;
- differentiating into the wrong types of cells
Current research into the
treatment of red-green colour
blindness involves the use of
induced pluripotent stem cells
(iPS cells).
Suggest how iPS cells could
correct red-green colour
blindness.
- (iPS cells) divide;
- (iPS cells) develop/differentiate into (green sensitive) cones
The use of iPS cells could have
advantages over the use of
gene therapy to correct red-
green colour blindness
- (Use of iPS cells) long-term;
Accept ‘gene therapy short-term’ or ‘only two years’
Accept ‘permanent’ - (Use of iPS cells) less chance of rejection/immune response;
- (Use of iPS cells) single treatment;
Accept ‘gene therapy ‘regular/frequent treatment’’ - Harm/side effects from using viruses (in gene therapy);
Suggest how transcription
factors can reprogramme cells
to form iPS cells.
- Attach to gene / DNA / promoter region;
- Stimulate / inhibit transcription / RNA polymerase;
Describe how alterations to
tumour suppressor genes can
lead to the development of
tumours.
- (Increased) methylation (of tumour suppressor genes);
- Mutation (in tumour suppressor genes);
- Tumour suppressor genes are not transcribed/expressed
OR
Amino acid sequence/primary structure altered; - (Results in) rapid/uncontrollable cell division;
Give one way in which benign
tumours differ from malignant
tumours.
Cells of benign tumours cannot spread to other parts of the body / metastasise;
OR
Cells of benign tumours cannot invade neighbouring tissues.
Lactase persistence is caused
by a mutation in DNA. This
mutation does not occur in the
gene coding for lactase.
Suggest and explain how this
mutation causes LP.
- Mutation in promoter (DNA/gene) for transcription factor
OR
Mutation in promoter (region/DNA) for the gene
OR
Mutation in gene for transcription factor;
Accept mutation in an epistatic gene - Lactase gene continues to be transcribed/active;
What is meant by a genome?
(All) the DNA in a cell/organism;
Describe the roles
of two named types of
enzymes used to insert DNA
fragments into plasmids.
- Restriction (endonuclease/enzyme) to cut plasmid/vector;
- Ligase joins gene/DNA to plasmid/vector;
Describe how a geneticist
would attempt to insert copies
- Cut the plasmid with a restriction endonuclease;
Allow ‘add base sequences to blunt ends of plasmid and HGH gene’ - (So that) both have complementary / sticky ends;
- (Mix together) and add ligase to join the complementary /
sticky ends;
To enable her to identify which
bacteria have taken up the
plasmid with the gene, the
plasmids she intends to use
contain a gene that codes for a
green fluorescent protein
(GFP).
Suggest one advantage of using this gene for GFP to identify bacteria that have taken up plasmids.
Can quickly identify transformed bacteria using UV light
From a sample of mitochondrial
DNA:
* how would enough DNA
be obtained for sequencing?
* how would sequencing
allow the identification of a
mutation?
- Enough DNA using PCR;
- Compare DNA sequence with ‘normal’ DNA.
What is a DNA probe?
- (Short) single strand of DNA;
- Bases complementary (with DNA/allele/gene);
Describe how DNA can be
broken down into smaller
fragments.
- Restriction endonuclease/enzyme;
- (Cuts DNA at specific) base sequence
OR
(Breaks) phosphodiester bonds
OR
(Cuts DNA) at recognition/restriction site;
In electrophoresis, the DNA on
the nylon membrane is treated
to form single strands. Explain
why.
(So DNA) probe binds/attaches/anneals;
Suggest two features of the
structure of different proteins
that enable them to be
separated by gel
electrophoresis.
- Mass/number of amino acids/polypeptides;
- Charge;
- R groups (differ);
Explain the role of reverse
transcriptase in RT-PCR
Produces (c)DNA using (m)RNA;
Explain the role of DNA
polymerase in RT-PCR.
Joins nucleotides to produce (complementary strand/s of) DNA;
Define what is meant by
epigenetics.
- Heritable changes in gene function;
- Without changes to the base sequence of DNA;
Explain how increased
methylation could lead to
cancer.
- Methyl groups (could be) added to (both copies of) a tumour
suppressor gene; - The transcription of tumour suppressor genes is inhibited;
- Leading to uncontrolled cell division.
Suggest and explain one way
epigenetics may affect the age
when symptoms of
Huntington’s disease start,
caused due to an increase in
the protein huntingtin.
- (Increased) methylation of DNA/gene/allele;
Reject acetylation of DNA.
Accept gene expression for transcription but ignore gene switched
on/off.
Ignore methylation of histones.
Accept DNA-histone complex as equivalent to histone(s). - Inhibits/prevents transcription;
OR - Decreased methylation of DNA/gene/allele;
- Stimulates/allows transcription;
OR - Decreased acetylation of histone(s);
- Inhibits transcription;
OR - Increased acetylation of histone(s);
- Stimulates/allows transcription;
types of stem cells
totipotent
pluripotent
multipotent
unipotent
induced pluripotent stem cell
stem cell
undifferentiated cells that can continually divide and become specialised
totipotent stem cell
- can differentiate into any body cell
- occur for a limited time in early mammalian embryos
pluripotent stem cell
- can differentiate into almost any body cell
- occur in embryos
multipotent stem cells
- can differentiate into a limited number of cells
- found in mature mammals e.g in bone marrow
unipotent stem cell
can differentiate into one type of cell
found in mature mammals
induced pluripotent stem cell
- produced from adult somatic cells
- using protein transcriptional factors
- overcomes ethical issues of using embryonic stem cells
