Lecture 15 - How do genes make cells?

Question 1

How does DNA make you?

Answer 1

Allows cells to do complicated things - respond to the environment, make and break molecules, generate energy and maintain itself

Question 2

Typical human cell

Answer 2

50% protein
40% lipids
10% carbohydrates

Question 3

Building blocks

Answer 3

Carbon chains
Sugars
Amino acids
Sugar+base+phosphate

Question 4

Macromolecules

Answer 4

Lipids
Complex carbohydrates
Proteins
Nucleic acid (RNA/DNA)

Question 5

Supramolecular assemblies

Answer 5

Membranes
Ribosomes
Chromosomes

Question 6

Organelles

Answer 6

Nucleus
Golgi
ER
Mitochondria

Question 7

Every protein has

Answer 7

a specific role in the cell

Question 8

__________ is the key to life

Answer 8

regulation

Question 9

What is a gene?

Answer 9

Section of DNA that codes for a protein

Question 10

Central dogma of genetics

Answer 10

DNA to RNA to Protein

Question 11

What is transcriptional control?

Answer 11

Determines when and in what cells a gene is transcribed to produce mRNA. It is therefore the first step determining how many individual proteins are produced in a cell.

Question 12

Why is a brain cell different from a heart cell?

Answer 12

Every cell has the same DNA and the same ~21,000 protein coding genes.

• In any cell type about 11,000 to 17,000 genes are expressed;
• 10,000 of these genes are expressed in all cells (needed for basic cellular functions)
• About 1,000 to 2,000 are unique to a specific cell type – these genes make, say, a brain cell different from a heart cell
The rest are expressed in some but not all cell types

Reason why cells are different is because they have different content/expressions of genes

Question 13

Transcription

Answer 13

The process where a DNA sequence is copied (transcribed) into an RNA molecule

A gene is said to be ‘turned on’ or ‘expressed’ when it is transcribed.
Transcription is a key control point:
•If a gene is transcribed, it is can used to mak a protein (expressed). - can be translated
•If a gene is not transcribed in a cell, it can’t be used to make a protein in that cell. - cannot be translated

Question 14

Translation

Answer 14

Process by which mRNA is decoded and a protein is produced

Question 15

Transcription factors

Answer 15

Are proteins that bind to a specific DNA sequence and control the rate of transcription (DNA to RNA)

Collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription.

Binds very specific parts of DNA, only interact with DNA with specific sequence (10-30 bps can be roughly recognised by a transcription factor)

Transcription factors are proteins that turn genes on and off

Question 16

How do transcription factors work?

Answer 16

Need activator/s present and repressor absent

Transcription factors then recruit RNA polymerase (get complex formation)

Question 17

Gene regulation

Answer 17

ability of an organism to control which genes are transcribed in response to the environment

Question 18

Regulatory regions of a gene

Answer 18

Promoter - the DNA sequence at which transcription factors bind and recruit RNA polymerase. Determines if and how much a gene is transcribed. Contains short sequences that transcription factors bind to.

Question 19

Transcribed region of a gene

Answer 19

Transcribed region - sequences of DNA that are copied into RNA (transcribed). The transcribed RNA (pre-mRNA) is processed so that it can be translated (e.g. the intron sequences are removed)

contains the information that specifies an amino acid sequence

Question 20

Two types of transcription factors

Answer 20

Activators and repressors

Question 21

Activators

Answer 21

Allows transcription to happen by recruiting RNA polymerase to the promoter

Question 22

Repressors

Answer 22

Prevents transcription from occurring by preventing RNA polymerase from binding to the promoter

Question 23

Pancreatic beta cell vs liver cell

Answer 23

Pancreatic beta cell 
Transcription factor (TF) activators for the insulin gene made. TF repressors for insulin gene are NOT made. TF activators for glycogen synthase gene NOT made. TF repressors for glycogen synthase gene is made. 

Liver cell
TF activators for insulin gene are NOT made. TF repressors for insulin gene are made. TF activators for glycogen synthase gene are made. TF repressors for glycogen synthase gene are NOT made.