Regulatory gene - answer-a gene that codes for a transcription factor, so controls the expression of structural genes
Structural gene - answer-gene that codes for polypeptide
Mutation - answer-a random change in the sequence of bases in an individual gene, or in the structure of the chromosom...
Regulatory gene - answer-a gene that codes for a transcription factor, so controls the expression of
structural genes
Structural gene - answer-gene that codes for polypeptide
Mutation - answer-a random change in the sequence of bases in an individual gene, or in the structure
of the chromosome (which changes the sequence of genes on the chromosome)
Examples of mutagenic agents - answer-x-rays, uv light (physical), nitrous acid (chemical) & some viruses
(biological agents)
What can chromosomal mutations also do? - answer-alter the chromosome no of the individual
What can cause chromosomal mutations? - answer-- deletion
- inversion
- translocation
- duplication
- non-disjunctionexa
What are the 3 types of substitution mutations? - answer-- silent - there's a change in the base
sequence, but it still codes for the same aa
- missense - a change to the base sequence that leads to a change in the aa sequence in a protein
- nonsense - a point mutation may alter a base triplet, so it becomes a stop codon. This stops
transcription and results in a truncated protein
How can a mutation in a gene lead to a truncated protein? - answer-1. A mutation in the dna can lead to
a stop codon
2. Translation is terminated by the stop codon
3. No more aas are added after the stop codon
How can a mutation in a gene lead to a non-functioning enzyme? - answer-1. There is a change in the
base sequence of the gene, leading to a change in the aa sequence of an enzyme
2. This results in a change in the hydrogen, ionic, or disulphide bonds
3. Leading to a change in the tertiary structure, and the shape of the active site in the enzyme
4. So the substrate is no longer complementary
5. And can't bind to the active site so no e-s complexes form
Characteristics of down's syndrome - answer-- an individual receives 3 copies of chromosome 21 instead
of 2 due to translocation of a chromosome
,- people with down's syndrome have learning difficulties & thick set bodies
Transcription factors - answer-proteins, or short non-coding rna, that can combine with a specific site on
a length of dna and inhibit or activate transcription of the gene
What does e. Coli usually use as a respiratory substrate? - answer-glucose
What does e. Coli use when this is absent? - answer-lactose, because it induces the production of the
enzymes lactose permease, which allows lactose to enter the bacterial cell, and b-galactosidase, which
hydrolyses lactose to glucose & galactose
What happens in the lac operon in the presence of lactose? - answer-1. Mrna is transcribed by the
regulatory gene
2. The repressor protein is translated from the mrna strand
3. Lactose binds to the repressor protein & changes its shape
4. This stops it binding to the operator region
5. So rna polymerase binds to the promoter region
6. The structural genes z & y are transcribed into mrna
7. The mrna is translated into lactose permease & b-galactosidase
At what level does the lac operon control gene expression? - answer-transcriptional level
Regulatory mechanisms that control gene expression at post-transcriptional level - answer-- primary
mrna is modified
- introns are removed to produce mature mrna
- alternative splicing can produce different versions of mrna
Regulatory mechanisms that control gene expression at post-translational level - answer-- proteins must
be activated by camp by phosphorylation
- the binding of camp alters the shape of the protein
-it alters the 3d structure of the protein by phosphorylation, in which a pi group is attached to the
protein
Homeobox gene - answer-a homeotic gene that contains a homeobox sequence consisting of 180 base
pairs that codes for a homeodomain sequence
What does the homeodomain sequence do? - answer-binds to dna & acts as a transcription factor. It
initiates transcription and is involved in the control of development & the body plan
Why are homeobox genes similar in plants, animals and fungi? - answer-- there has been very little
change by mutation in homeobox genes because these genes are very important & mutation would alter
the body plan
- many other genes would be affected so the mutation would be likely to be lethal
Hox genes - answer-a subset of homeobox genes, found only in animals; involved in formation of
anatomical features in the correct locations of the body plan.
Apoptosis - answer-programmed cell death
, The process of apoptosis - answer-1. Enzymes break down the cell cytoskeleton
2. The cytoplasm becomes dense with tightly packed organelles
3. Blebs form from the plasma membrane
4. Chromatin condenses, the nuclear envelope breaks & dna breaks into fragments
5. The cell breaks into vesicles that are removed by phagocytosis
6. So the cell debris isn't released into surrounding tissue
At what level do hox genes & apoptosis control gene expression? - answer-development
Why can failure of the control mechanisms during development lead to deformities? - answer-- it can
stop apoptosis occurring
- hox gene doesn't produce the transcription factor
- molecules signalling apoptosis aren't produced
How can meiosis lead to genetic variation? - answer-- independent assortment of homologous
chromosomes in metaphase i
- independent assortment of chromatids in metaphase i
- so homologous chromosomes come from different parents. This produces a large number of allele
combinations
- crossing over in prophase i, so chromatids will have a new combination of alleles
- random mutations change the base sequence
- non-disjunction, where chromosomes do not separate in metaphase i
- random fertilisation of gametes
- gametes are not genetically identical
Example of the environment interacting with genes - answer-chlorosis in plants, which occurs when
leaves don't develop enough chlorophyll if the soil plants are grown in doesn't contain enough
magnesium
Homologous chromosomes - answer-a pair of 1 maternal & 1 paternal chromosome, that are the same
length and have genes at the same loci
Sister chromatids - answer-the 2 identical chromatids produced when a chromosome has replicated
Gene - answer-a sequence of bases that codes for a polypeptide
Locus - answer-position of a gene on a chromosome
Allele - answer-a version of a gene.
Phenotype - answer-observable characteristics of an organism
Genotype - answer-alleles present within the cells of an individual for a particular characteristic
Dominant - answer-a characteristic in which the allele responsible is expressed in the phenotype, even in
those with heterozygous genotypes
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