Gene Expression-Topic 8A Flashcards
When might gene mutations occur?
During DNA replication
What is a mutation?
A change to the base (nucleotide) sequence of DNA
What is Substitution?
One or more bases swapper e.g.
AT G C becomes AT T C
What is Addition/ Insertion
One or more bases added so ACTG becomes ACATG
What is Deletion?
One or more bases removed so
ACTG becomes CTG
What is Duplication?
One or more bases repeated so ATGCCT becomes ATGCCCCT
What is Inversion?
A sequence of bases is reversed e.g A TGCC T becomes A CCGT T
What is Translocation? (type of mutation)
A sequence of bases is moved from one location in the genome to another (within same OR different chromosome)
How is the rate of mutation increased?
Mutagenic agents
Gene mutations occur ………
spontaneously
Which types of mutations cause a frameshift?
Additions, duplications and deletions
What is a frame shift?
a shift in the base triplets that mean that the triplet code is read in a different way.
What is epigenetics?
Heritable changes in gene function caused by changes in environment without change to base sequence of DNA
Ways that transcription is inhibited by:
increased methylation
decreased acetylation
Describe the effect of decreased acetylation of histones on the transcription of genes they are associated with. [3]
Decreased acetylation = more highly condensed DNA-Histone complex
therefore transcription factor cannot access DNA
and DNA can’t be transcribed.
What are totipotent cells?
Early embryonic stem cell that can divide and produce any type of body cell.
What are pluripotent cells?
Pluripotent stem cells can divide in unlimited numbers and can be used in treating human disorders
What are multipotent cells?
stem cells found in mature mammals and can divide to form a limited number of different cell types.
What are unipotent cells?
stem cells found in mature mammals and can divide to form a limited number of different cell types.
What are induced pluripotent cells? (iPS)
Induced pluripotent stem cells (iPS cells) can be produced from adult somatic cells using protein transcription factors
Example of unipotent cells dividing into
cardiomyocytes (cells of heart)
Explain how an activated oestrogen
receptor affects the target cell. [2]
Transcription factor binds to promoter region which stimulates RNA polymerase
which increases transcription
Oestrogen only affects target cells. Explain why oestrogen does not affect other cells in the body. [1]
As only oestrogen has those specific receptors
Describe how translation can epigenetically control gene expression ?
Double stranded RNA broken by enzyme into siRNA
1 of these strands now combines with enzyme
siRNA strand pairs up with complementary bases on mRNA strand.
The enzyme cuts the mRNA into smaller sections
How does oestrogen enter the cytoplasm where transcriptional factor is?
Diffuses through the phospholipid bilayer as it is lipid soluble
Name a transcriptional factor that initiates transcription
Oestrogen
What is transcription of genes controlled by?
Transcription factors
What is a suppressor?
Transcription factors that inhibit gene expression
Transcription factors move from the ….. to the …..
cytoplasm to the nucleus
How do activators work?
Help RNA polymerase bind to the start of a target gene, and activate transcription.
How do suppressors work?
Bind to the start of target gene preventing RNA polymerase from binding, stopping transcription.
