Lecture 8 Flashcards
What is a genome?
sum total of genetic material of an organism
How does most of the genome exist?
most of the genome exists in the form of chromosomes
Do genome viruses contain dna or rna?
either one
What is a chromosome?
discrete cellular structure composed of a neatly packaged DNA molecule
4 facts about eukaryotic chromosomes?
DNA wound around histones
located in the nucleus
diploid (in pairs) or haploid (single)
linear appearance
2 facts about prokaryotic chromosomes
DNA condensed into a packet by means of histone-like proteins
single, circular chromosome
What is classical genetics of a gene?
the fundamental unit of heredity responsible for a given trait in an organism
What is molecular and biochemistry of a gene?
site on the chromosome that provides information for a certain cell function
What is a gene?
- a certain segment of DNA that contains the necessary code to make a protein or RNA molecule
- segment of DNA that contains code to make a group of related proteins or RNAs
What is the central theme of biology?
Central theme of biology: information flows from DNA to RNA to protein
what is transcription?
master code of DNA used to synthesize an RNA molecule
What is translation?
transcribed RNA used to produce protein
What do rna viruses do?
RNA viruses convert RNA to other RNA
What do retroviruses do?
retroviruses convert RNA to DNA
What are a wide variety of rna used to do?
A wide variety of RNAs are used to regulate gene function
What is a codon?
groups of three nucleotides that dictate which amino acid is added to the growing peptide chain
what are the 3 differences between eurkaryotic and prokaryotic transcription and translation?
Start codon is AUG for both, but in eukaryotes, it codes for a different form of methionine
Eukaryotic mRNAs code for just one protein, unlike bacterial mRNAs, which often contain information from several genes in series
Eukaryotic transcription takes place in the nucleus and must pass through pores in the nuclear membrane to the cytoplasm for translation
Eukaryotic genes do not exist as an uninterrupted series of triplets coding for a protein
What are introns?
intervening sequence of bases that do not code for a protein
What are exons?
coding regions that will be translated into proteins
What are plasmids?
small, circular pieces of DNA that contain their own origin of replication
can replicate independently of the bacterial chromosome
found in many bacteria
contain genes that confer useful traits, such as antibiotic resistance
what is conjugation?
- Mode of genetic exchange in which a plasmid or other genetic material is transferred by a donor to a recipient cell via a direct connection
- requires the attachment of two related species and the formation of a bridge that can transport DNA
What is transformation?
entails the transfer of naked DNA and requires no special vehicle
What is transduction?
DNA carried from one bacterium to another via a bacterial virus
How does gram negative conjugation work?
- fertility (F’ factor) allows the synthesis of a conjugative pilus
- recipient cell has a recognition site on its surface
- F+: cell that has the plasmid
- F-: cell that lacks the plasmid
- contact is made when a pilus grows out from the F+ cell, attaches to the surface of the F- cell, contracts, and draws the two cells together
how does gram positive conjugation work?
an opening is created between two adjacent cells
replicated DNA passes across from one cell to another
How do you capture dna from a solution?
A chromosome released by a lysed cell breaks into fragments small enough to be accepted by a recipient cell
does dna in a dead cell still retain its genetic sequence?
yes
What is transformation?
nonspecific acceptance by a bacterial cell of small fragments DNA from the environment
facilitated by DNA-binding proteins on the cell wall
What are competent cells in transformation?
cells that are capable of accepting genetic material
What is transfection?
similar process carried out in eukaryotic cells to form genetically modified yeasts, plants, and mice
What are transposons?
Transposable elements capable of shifting from one part of the genome to another; “jumping genes”
Can be transferred from a chromosome to a plasmid, or vice versa; or from one cell to another in bacteria and some eukaryotes
What are transposons involved in?
changes in traits such as colony morphology, pigmentation, and antigenic characteristics
replacement of damaged DNA
intermicrobial transfer of drug resistance (in bacteria)
What is a spontaneous mutation?
errors in transcription
What is an induced mutation?
mutagens (chemicals or uv light)
What is a point mutation?
a mutation affecting only one or very few nucleotides in a gene sequence
what is an insertion?
an added gene
What is a deletion?
a deleted gene
What is a missense mutation?
Affects proteins
Nonfunctional, functions incorrectly, no effect on protein
What is a nonsense mutation?
causes protein not to be completely formed, usually nonfunctional protein
What is a silent mutation?
results in same protein being made even though there is a mutation present
What is a back-mutation?
mutation is corrected back to original sequence
What is a frameshift mutation?
place where start reading DNA to make protein is moved, so miss part of protein
What is excision repair?
enzymes break the bonds between the bases and the sugar-phosphate strand at the site of the error
a different enzyme removes the defective bases one at a time
the remaining gap is filled in by DNA polymerase I and ligase
What is ames test?
Test for mutagenic chemicals
