From Gene To Protein

Question 1

Gene expression

Answer 1

Three main steps:

Transcription抄写
of RNA from DNA

Processing
of the pre-mRNA transcript

Translation 翻译
of the mRNA transcript to a protein

Question 2

Gene expression is tightly regulated

Answer 2

Multiple control points:

Transcription抄写 factors need to assemble集合, and DNA needs to be accessible可访问的.

capping限制, the extent程度 of polyadenylation聚腺苷酸化, alternate交替 splicing剪接, producing an mRNA able to be translated

specific proteins assist协助 in nuclear export of mRNA

regulatory监管 proteins can block translation翻译, variable变量的 mRNA life-spans运行周期

Question 3

Why is control of gene expression important?

Answer 3

Housekeeping(commonly used) proteins are continuously produced
•protein and mRNA are present in large quantities (e.g.Tubulin)
•typically have longer “half-life” in cells

Question 4

Why is control of gene expression important?

Answer 4

Other proteins are produced in response to stimuli刺激 as required

• cell signalling (e.g.ligand配位体 binding a cell surface receptor, or activating激活 an intracellular细胞内 receptor受体)
• signal transduced转导 and may enter the nucleus to activate transcription
• results in the production of a short-lived protein to carry out the required function

Question 5

Transcription – an overview

Answer 5

Three steps:

1. Initiation 初始化
2. Elongation 伸长
3. Termination 终止