SECTION 19: CELLULAR CONTROL

Question 1

6.1.3 GENE MUTATIONS
What are mutations?

Answer 1

Any change to the base (nucleotide) sequence of DNA is called a mutation

Question 2

6.1.3 GENE MUTATIONS
What is substitution?

Answer 2

One or more bases are swapped for another base, e.g. ATGCCT becomes ATICCT (G is swapped for T).

Question 3

6.1.3 GENE MUTATIONS
What is deletion?

Answer 3

one or more bases are removed, e.g. ATGCCT becomes ATCT (GC is removed).

Question 4

6.1.3 GENE MUTATIONS
What is insertion?

Answer 4

one or more bases are added, e.g. ATGCCT becomes
ATGACCT (A is added).

Question 5

6.1.3 GENE MUTATIONS
What is a framework mutation?

Answer 5

Some mutations can have a huge effect on the base sequence of a gene.
For example, adding or deleting a base changes the number of bases present, causing a shift in all the base triplets that follow.

This is called a frameshift mutation - when an insertion or deletion changes the way the rest of the base sequence is read.

The earlier a frameshift mutation appears in the base
sequence, the more amino acids are attected and the greater the mutation’s effect on the protein.

Question 6

6.1.3 GENE MUTATIONS
What are a few reason for a neural effect?

Answer 6

The mutation changes a base in a triplet, but the amino acid that the triplet codes for doesn’t change. This happens because some amino acids are coded for by more than one triplet.

The mutation produces a triplet that codes for a different amino acid, but the amino acid is chemically similar to the original so it functions like the original amino acid.

The mutated triplet codes for an amino acid not involved with the protein’s function.

Question 7

6.1.3 GENE MUTATIONS
What is the effect of a neural effect?

Answer 7

Won’t affect an organism overall ok protein function

Question 8

6.1.3 GENE MUTATIONS
What are the beneficial effect of mutation?

Answer 8

These have an advantageous effect on an organism, i.e. they increase its chance of survival.

Mutations that are beneficial to the organism are passed on to future generations by the process of natural selection.

Question 9

6.1.3 GENE MUTATIONS
What are the harmful effect of mutation?

Answer 9

These have a disadvantageous effect on an organism, i.e. they decrease its chance of survival.

Mutations can also affect whether or not a protein is produced. E.g. if a mutation occurs at the start of a gene, so that RNA polymerase can’t bind to it and begin transcription, the protein coded for by the gene won’t be made.
The loss of production of a protein can have harmful effects — some genetic disorders are caused by this.

Question 10

6.1.1 REGULATING GENE EXPRESSION
How is gene expression at the transcription level in prokaryotes work with no lactose present?

Answer 10

• Regulator gene expressed - transcribed
• mRNA translated into a repressor protein
• Repressor protein binds to operator region of lac operon, covering the promoter region.
• This prevents RNA polymerase from binding the promotor region
• No transcription of structural genes
• Enzymes are not induced

Question 11

6.1.1 REGULATING GENE EXPRESSION
How is gene expression at the transcription level in prokaryotes work with lactose present in medium?

Answer 11

Regulator gene expressed - transcribed
• mRNA translated into a repressor protein
• Lactose (inducer) binds to repressor protein changing its confirmation.
• Repressor protein can no longer bind to the operator region.
• Therefore, RNA polymerase can bind to the promoter region
• Structural genes are transcribed into mRNA
• mRNA translated into the enzymes needed for lactose metabolism.

Question 12

6.1.1 REGULATING GENE EXPRESSION
What is gene regulation?

Answer 12

the process of controlling which genes in a cell’s DNA are expressed (used to make a functional product such as a protein)

• how a cell controls which genes, out of the many genes in its genome, are “turned on” (expressed).
• Different cells in a multicellular organism may express very different sets of genes, even though they contain the same DNA.
• These different patterns of gene expression cause various cell types to have different sets of proteins, making each cell type uniquely specialized to do its job.

Question 13

6.1.1 REGULATING GENE EXPRESSION
What are the factors affecting gene expression?

Answer 13

• Different cell types express different sets of genes. However, two different cells of the same type may also have different gene expression patterns depending on their environment and internal state.

• A cell’s gene expression pattern is determined by information from both inside and outside the cell.
• from inside the cell: the proteins it inherited from its mother cell, whether its DNA is damaged, and how much ATP it has.
• from outside the cell: chemical signals from other cells, mechanical signals from the extracellular matrix, and nutrient levels.

Question 14

6.1.1 REGULATING GENE EXPRESSION
What are the stages of gene regulation?

Answer 14

• Transcriptional level
• Post-transcriptional level
• Post-translational level

Question 15

6.1.1 REGULATING GENE EXPRESSION
What are transcription factors?

Answer 15

Activators and receptors

Question 16

6.1.1 REGULATING GENE EXPRESSION
What are activators?

Answer 16

Factors that start transcription

Question 17

6.1.1 REGULATING GENE EXPRESSION
What are repressors?

Answer 17

Stop transcription

Question 18

6.1.1 REGULATING GENE EXPRESSION