8.3 Study Guide

Question 1

What is transcription and what is a central dogma?

Answer 1

Transcription: The process by which RNA is made by copying portions of DNA.

Central Dogma: The process by which genetic information flows from DNA to RNA to Protein. DNA replicates itself and the proteins ultimately lead to the formation of our traits.

Question 2

What are the base pairing rules for RNA?

Answer 2

Adenine binds with Uracile (A to U) and Cytosine binds with Guanine (C to G).

Question 3

What are the differences and similarities between DNA and RNA?

Answer 3

DNA: Deoxyribose molecule, nitrogenous bases: A, C, G, T. Sugar only has a hydrogen molecule, double helix (2 strands), stores genetic information
RNA: Ribose molecule, nitrogenous base: A, C, G, U. Sugar has a hydroxyl group (OH), single strand, folds over itself, temporary carrier of genetic information, Transfer RNA and ribosomes synthesize proteins.
Both: Both made of nucleotides, pentose sugar, both contain nucleotides made out of phosphates, sugars, and nitrogenous bases. Helix of sugar phosphates. Hydrogen bonds between base pairs.

Question 4

What are the parts of a eukaryotic gene?

Answer 4

Enhancer/Silencer: Additional binding site for transcription factors, act as an on/off switch, controls if/how much RNA is made from a gene
Promoter: Start site of transcription, most eukaryotic promoters contain a “TATA”box, signals transcription factors and then RNA Polymerase attach
Exons: Sequences that will be present in the mRNA, exit the nucleus
Introns: Will be spliced out and removed

Question 5

What are the stages of transcription?

Answer 5

1. Initiation: Transcription factors bind to promoter/enhancer regions, attract and prepare RNA Polymerase to begin copying gene sequence into mRNA.
2. Elongation: RNA Polymerase breaks free of Transcription Factors, a protective 5’ cap is added to RNA, splicing occurs, as RNA Polymerase copies DNA, other proteins are recruited to splice out introns.
3. Termination: At the polyadenylation site, the termination sequence is recognized and cut, a Poly A tail is added to the end of the RNA molecule, longer the tail= longer the mRNA will be in the cytoplasm= more protein can be made.

Question 6

What happens during the splicing process?

Answer 6

RNA splicing: edit out introns, makes mature mRNA transcript, only happens in eukaryotes

Question 7

What happens during alternative splicing?

Answer 7

Alternative mRNAs are produced from the same gene. Keep different combinations of Exons, different RNA sequences result in different protein structures/functions.
The gene itself remains unchanged.