6.1 - Cellular Control

Question 1

How is gene expression controlled at the Transcriptional Level?

Answer 1

Altering the rate of transcription of genes

Question 2

What are Transcription Factors?

Answer 2

Proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription.
Increase - Activators
Decrease - Repressors

Question 3

How do Transcription Factors work in Eukaryotes?

Answer 3

They bind to specific DNA sites near the start of their target genes. (The genes they control the expression of.

Question 4

How do Transcription Factors work in Prokaryotes?

Answer 4

They bind to operons.

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

Question 5

What happens when Lactose isn’t present in the Lac Operon?

Answer 5

Regulatory gene (LacI) produces the lac repressor, which binds to the operator site (Acts as a transcription Factor).
The blocks transcription as RNA polymerase can’t bind to the promoter.

Question 6

What happens when Lactose IS present in the Lac Operon?

Answer 6

Lactose binds to the repressor, changing its shape, so it can no longer bind to the operator site.
RNA polymerase can now begin transcription of the structural genes.

Question 7

What are introns and exons?

Answer 7

Introns: non coding regions of DNA

Exons: Coding regions of DNA

Question 8

What are the levels Gene expression can be controlled at?

Answer 8

Transcriptional
Post transcriptional
Post translational

Question 9

What happens at the post transcriptional level?

Answer 9

mRNA is edited into mature mRNA.

Question 10

How is mRNA converted to mature mRNA

Answer 10

During transcription both introns and exons are copied which forms primary mRNA.
Introns are removed in splicing, and exons are joined.
This forms mature mRNA.

Question 11

How does Post translational Level control gene expression?

Answer 11

Proteins have to be activated by hormones or sugars.
These usually result in the release of cAMP, which in turn activates the cell.

Question 12

What is a body plan?

Answer 12

The general structure of an organism.

Question 13

What are Hox genes?

Answer 13

They code for proteins which control body plan development.
They contain regions called homeobox sequences

Question 14

What does it mean that homeobox sequences highly conserved?

Answer 14

They have changed very little during evolution.

Question 15

How do Hox genes control development?

Answer 15

Homeobox sequences code for a part of a protein called the homeodomain.

The homeodomain bind to specific DNA sites, enabling the protein to work as a transcription factor.

The proteins bind to DNA at the start of developmental genes, activating or repressing transcription.

Question 16

What is Apoptosis?

Answer 16

Programmed cell death.

Question 17

How does apoptosis work?

Answer 17

Enzymes inside the cell break down important cell components, such as proteins in cytoplasm

Cel begins to shrink and breaks up into fragments.

Cell fragments are engulfed by phagocytes and digested.

Question 18

What are the 3 types of Mutation?

Answer 18

Substitution - Base swapped for another
Deletion- Base removed
Addition - Base added.

Question 19

Why can mutations cause no effect?

Answer 19

Triplet code is degenerate, so multiple codons code for the same amino acid.

Mutation may code for a different amino acid, but it’s chemically similar to the original one.

Mutated codon is not involved in proteins function.

Question 20

Why can Mutations be beneficial?

Answer 20

A mutation may lead to antibiotic resistance is bacteria, which allows them to survive.

Question 21

Why can mutations have harmful effects?

Answer 21

A deletion of 3 bases in the gene which codes for an important protein.