lecture 5- genes

Question 1

gene=

Answer 1

basic unit of heredity and sequence of nucleotides in DNA or RNA(viruses)
- gene is a segment of a nucleic acid that carries the code for a particular protein or for a functional non-coding DNA

Question 2

central dogma

Answer 2

gene(DNA) — mRNA — protein — function

Question 3

difference between living cells and gene creatures

Answer 3

living cells: bacteria, archaea, eukaryotes

gene creatures: have to be inside living cell to propagate - DNA/RNA viruses, plasmids, viroids, transposons
- difference between living cells and gene creatures is plasma membrane

Question 4

DNA cloning

Answer 4

• isolate a fragment of chromosome (DNA segment) to be cloned by digestion with restriction enzymes (endonucleases)
• select small molecule of DNA capable of self replication (cloning vectors) and digest with restriction enzymes
• join 2 DNA fragments covalently (DNA ligase)- recombinant DNA
• move recombinant DNA from test tube to host cell (most common: E. coli), provide machinery for DNA replication
• identify host cells with recombinant DNA (selectable markers: permit the growth of cell or kill cell under standard conditions)

Question 5

Recombinant DNA technology enzymes

Answer 5

type II restriction endonuclease- cleaves DNA at specific base sequences
DNA ligase- joins two DNA molecules or fragments

endo and exonucleases- DEGRADATION
endonucleases- attack internal bonds
exonucleases- nibble from ends (5’ or 3’)
DNA endonucleases- called restriction enzymes (molecular scissors)- break
phosphodiester bonds

Question 6

recognition sequences for restriction enzymes are usually ___

Answer 6

4-8 bp long and palindromic

Question 7

what are plasmids

Answer 7

circular DNA molecule that replicates separately from the host chromosome
- sequence of DNA in plasmids keeps bacteria resistant to antibiotics

Question 8

cloning vectors (factors)

Answer 8

molecule that amplifies the fragment
- common cloning factor is plasmids (also bacterial artificial chromosomes BAC’s, yeast artificial chromosomes YAC’s)

ex of plasmid cloning factor = pBR322
- has origin of replication (controlled well, going to have many copies of plasmid in host cells)
- has resistance to 2 antibiotics
- has restriction sites for different recognition enzymes- to cut plasmid and release DNA fragment
- if the gene for antibiotic resistance is cut, no longer has resistance

Question 9

name 5 PCR components

Answer 9

1- template DNA
2- oligonucleotide primers
3- DNA polymerase
4- dNTP’s
5- buffer to maintain pH and provide Mg2+

Question 10

PCR process

Answer 10

• PCR starts with denaturation of DNA strands with heating
  Taq DNA polymerase (thermus aquaticus)- stable at very high temps

3 stages: denaturation, annealing, elongation (each cycle has these 3 stages, repeats 30x)

Question 11

a nucleosome core is composed of

Answer 11

two copies of each core histone protein and 146 bp of DNA

Question 12

histone tails are sites for ___

Answer 12

extensive chemical modifications

Question 13

histone acetylation can disrupt the interaction between adjacent nucleosomes by…

Answer 13

preventing N-terminal tail of histones from interacting with the N-terminal tail of histones in the next nucleosome

Question 14

where would you most likely find chromatin in the beads on a string conformation

Answer 14

actively transcribed chromatin (euchromatin)

Question 15

genetic info in viruses and other gene creatures may be in the form of ____

genetic info in cellular organisms may be found in

Answer 15

RNA and DNA

DNA

Question 16

how can transformed cells having recombinant DNA be screened?

Answer 16

by selectable markers