Cellular Control

Question 1

What is a mutation ?

Answer 1

• A change in DNA base sequence caused by mutagens.

Question 2

What is a mutagen ?

Answer 2

• Outside factors that increase the rate of mutations

Question 3

What are the types of mutations ?

Answer 3

• Point Mutations
• Indel mutations

Question 4

What are the point mutations ?

Answer 4

• Only affects one base
• Substitution
• Insertion
• Deletion

Question 5

What causes a frameshift mutation? What is it?

Answer 5

• Insertion and Deletion disrupts triplet code reading .`

Question 6

Substitution definition

Answer 6

-A form of gene mutation in which one nucleotide base is exchanged for
another. This may change an amino acid or produce the same amino acid (due to the
degeneracy of the genetic code).

Question 7

Insertion defintion

Answer 7

-A form of gene mutation in which one or more nucleotide bases are added to a
DNA sequence. This may lead to a frameshift mutation, changing every successive codon.

Question 8

Deletion definition

Answer 8

• Deletion: A form of gene mutation in which one or more nucleotide bases are removed from a DNA sequence. This may lead to a frameshift mutation, changing every successive codon.

Question 9

What are the effects of a mutation

Answer 9

• Silent/Neutral - no effect (DNA degenerate)
• Beneficial - Enhanced function of protein (rare)
• Damaging/Harmful - Malfunctioning protein made

Question 10

What are the types of mutations ?

Answer 10

• Nonsense - codon due to particular mutation has changed into a stop codon
• Missense - particular amino acid change - degenerate coding has changing

Question 11

Explain how genes are ?

Answer 11

• Genes are switched on and off
• DNA carry the same genes but the structure and function of different cell varies
• This is because not all the genes are expressed (selectively switched on )
• They determine the cell structure and control cell processes.

Question 12

What levels can genes be controlled at ?

Answer 12

• Transcriptional
• Post- transcriptional
• Post translational level

Question 13

How is gene expression controlled at a transcriptional level ?

Answer 13

• Gene expression can be controlled at the transcriptional level by altering the rate of transcription of genes - e.g - increased transcription produces more mRNA which can be used to make more protein
• This can be controlled by transcription factors
• The shape of a transcription factor determines whether it can bind to DNA or not and can sometimes be altered by the binding of some molecules, e,g hormones and sugars
• • This means the amount of certain molecules in an environment or a cel can control the synthesis of some proteins by affecting transcription factors binding

Question 14

What is the difference between eukaryotes and prokaryotes at a transcriptional level ?

Answer 14

• In eukaryotes, transcription factors bind to specific DNA sites near the start of their target genes - the genes control the expression of.
• In prokaryotes control of gene expression often involves transcription factors binding to operons.

Question 15

What is a transcription factor ?

Answer 15

• They are proteins that bind to DNA and switch genes on or off by by increasing or decreasing the rate of transcription. Factors that increase the rate are called activators and those that decrease the rate are repressors.

Question 16

What is an operon ?

Answer 16

• A section DNA that contains a cluster of structural genes, that are transcribed together as well as control elements and sometimes a regulatory gene.

Question 17

What do structural genes code for ?

Answer 17

• They code for useful proteins such as enzymes