Cellular control

What is a mutation

An alteration to the DNA base sequence

What are addition and deletion mutations and why? [2]

• Where one or more nucleotides (bases) are either inserted or deleted from the DNA sequence

• More likely to be either harmful or beneficial, due to frame shift which means the entire amino acid sequence will be different

What is a substitution mutation? [2]

• When a nucletotide in the DNA sequence is replaced by another

• More likely to be a neutral mutation, meaning no change occurs in the amino acid sequence

How is gene expression regulated at the transcriptional level? [2]

• Transcription factors

• These are proteins that can either initiate or inhibit the transcription of genes, so that only certain parts of the DNA are expressed

Describe the function of the lac operon in low lactose concentrations [2]

• E.coli can use lactose as a respiratory substrate, via use of an enzyme

• When lactose concentration is low, the lac operon binds to the gene that makes this enzyme and inhibits its expression

Describe the function of the lac operon in high lactose concentrations [2]

• Lactose binds to the operon, causing it to change shape and unattach from the gene.

• Allows RNA polymerase to bind and the gene to be expressed

How is gene expression regulated at the post-transcriptional level? [2]

• This is done through splicing

• Primary mRNA contains both coding regions (exons) and non-coding (introns) regions

• The introns are removed to produce mature mRNA ready for translation

How is gene expression regulated at the post-translational level? [1]

• Activation of proteins,such as adrenaline through a second messenger system with cAMP

How is development controlled by homebox genes?

Code for transcription factors that activate genes when they’re needed during development of a zygote.

What is special about homebox genes?

Their sequences are similar in plants,animals and fungi

How is development controlled by mitosis? [2]

• Mitosis is the primary mechanism of growth

• Genes regulating mitosis respond to various stimuli, both internal and external, in order to control rate of growth

How is development controlled by apoptosis? [2]

• Programmes cell death

• It is highly controlled and keeps cell division at a constant rate as to prevent cancer

What are the three types of mutations to do with effects?

• Silent mutation

• Mid-sense

• Non-sense

What is a silent mutation?

No change in amino acid sequence

What is a mis-sense mutation?

A mutation that changes the amino acid coded for

What is a non-sense mutation?

A mutation that codes for a stop codon, causing protein synthesis to stop

What are epigenetics?

• Genetics affected by environmental factors

What is a homebox gene?

180 base pair amino acid sequence

What is a hox gene?

Gene responsible for body symmetry that is only found in animals

What is the process of apoptosis? [4]

• Intracellular enzyme that breaks down the cytoskeleton among other proteins, causing the cell to shrink

• Blebs form on cell surface membrane

• Cell breaks into vesicles

• Vesicles are engulfed by phagocytes