Transcription & Regulation of Gene Expression

Lecture 20

Do all human genes have introns?

no

What are autosomal chromosomes?

non-sex chromosomes

Define Gene

a locus(or region) of DNA that encodes a functional RNA or protein product and is the molcular unit of heredity.

What are histone proteins?

basic proteins that package and organize DNA into structural units called nucleosomes, which are the building blocks of chromatin

What are topoisomerases?

Enzymes that alter DNA supercoiling are called topoisomerases. These enzymes are required for DNA unwinding and rewinding during transcription and replication. There are two major types of topoisomerases
• Type I topoisomerases work by making a transient cut in

one DNA strand

• Type II topoisomerases work by making a transient cut in both DNA strands

How does type 1 topoisomerase work?

Type 1 topoisomerase transiently breaks 1 of 2 strands

How does type 2 topoisomerase work?

Type 2 breaks both strands, passes a dna sequence through the break, rejoin the strands

What is the promoter region?

a segment of DNA, located upstream of a gene, that acts as a binding site for RNA polymerase and transcription factors to initiate the transcription of that gene.

RNA Polymerases- Eukaryotes

RNA polymerase I- Riibosomal RNAs in nucleolus, RNA polymerase II- Messenger RNAs in nucleus , RNA polymerase III- 5S ribsomal RNA, small cellular RNAs, and viral RNAs.

Transcription factors

They are proteins that alter gene expression. They bind at specific sequences in DNA= a repsonse element. They are trans-acting factors!

Response element

is a cis-element(=DNA)