Chapter 24 - Genes, Genomes, and Chomosomes Flashcards
(28 cards)
Why are some genomes larger than they need to be fr pure protein encoding?
(1) Control elements (promoters)
(2) Gene copy number
(3) Duplicated genes
(4) Multigene familes
(5) Pseudogenes
(6) Intervening regions
(7) Repetitive sequence (SINE, LINE, Satellite DNA)
Control elements
Promoters, Terminators
Promoters
Binding sites for transcription factors that bind to DNA in a sequence-specific manner. Increases or decreases gene activity.
Gene copy number
Genes are directly copied. Variable/random. (ABC, ABBBC, AAABC, etc)
Duplicated genes
HIGHLY EXPRESSED genes are duplicated.
Multigene families
Variants of the same gene that may or may not be coordinately regulated. (All ON at the same time or OFF at the same time)
What does it mean that a group of genes are coordinately regulated?
They are all ON at the same time or OFF at the same time.
Pseudogenes
A member of a multigene family that lost transcription controls. There is no selective pressure to maintain the sequence.
Intervening regions
(Introns) Usually spliced out in eukaryotes
Introns
Intervening regions that are not expressed and usually spliced out.
Exons
Expressed regions.
Repetitive sequences
(1) SINE - short intervening sequences
(2) LINE - long intervening sequences
(3) Satellite DNA - very short tandem repeats
Satellite DNA
Very short tandem repeats more AT-rich than the bulk of DNA. Since AT-rich sequences are easier to break, satellite DNA are also common break points.
Why is satellite DNA called satellite DNA?
In a Cs-Cl gradient, satellite DNA give rise to “satellite” peaks on either side of the main DNA absorbance peak.
What are some kinds of DNA modification?
(1) Covalent modification/restriction
(2) Alteration of DNA (+repair)
(3) Recombination
(4) Amplification of gene copy #
(5) Inter-organism and inter-species DNA transfer
Why is there DNA methylation?
(1) Defense against foreign DNA
(2) Control of intiation of DNA replication origin (ORI)
(3) Mismatch DNA repair
What are the types of restriction/modification enzymes?
Type I, Type II, Type III
Type I restriction/modification enzyme
- Restriction endonuclease, methyl transferase, DNA binding specificity all on one complex
- Restriction site is NOT the same as DNA binding site
- Cuts many kb away
- Winds DNA around to cut (takes energy!)
Type II restriction/modification enzyme
- Restriction endonuclease and methyltransferase on separate proteins
- Recognition sequences are PALINDROME (MOM, DAD)
- Products of different restriction endonucleases –> different kinds of ends
- Recombinant DNA molecules can be constructed
Type III restriction/modification enzyme
- Restriction endonuclease and methyltransferase on same complex
- Cleavage not at binding site, but closer
- No ATP requirements
Type III restriction/modification enzyme
- Restriction endonuclease and methyltransferase on same complex
- Cleavage not at binding site, but closer
- No ATP requirements
What type of restriction/modification enzyme gave rise to recombinant DNA technology?
Type II
Nucleosomes
Histones + DNA
Histone octamer
(H2A, H2B, H3, H4)2 + H1
