Define genetics
the study of genes, how they carry information, how information is expressed, and how genes are replicated
Define genome
all the genetic information in a cell (chromosomes and plasmids)
Define chromosome
structures containing DNA that physically carry hereditary information; the chromosomes contain genes
Define gene
segments of DNA that encode functional products, usually proteins but also RNAs (ribosomal RNA, transfer RNA, microRNA)
Define genetic code
set of rules that determines how a nucleotide sequence is converted to an amino acid sequence of a protein
Define genotype
the genetic makeup of an organism (potential properties)
Define phenotype
physical characteristics of an organism (expressed properties), determined by its genotype
What are the characteristics of bacterial chromosome?
-Bacteria usually have a single circular chromosome made of DNA and associated proteins
-made of DNA and associated proteins
-comprises of millions of nucleotides
-much longer than the cell, bt only takes up ~10% of the cell's volume bcuz of supercoiled
-
Describe the structure of DNA and how it serves as genetic information.
-DNA is a polymer of nucleotides
-Each nucleotide consists of:
Deoxyribose (pentose sugar)
Phosphate group
Nitrogen-containing base: adenine (A), thymine (T), guanine (G), cytosine (C)
-DNA forms a double helix
-Base pairs:
-A pairs with T (2 H-bonds)
-C
Why is base pairing in DNA important?
-Complementary structure allows for the precise duplication of DNA during cell division
Describe the process of DNA replication, including the functions of DNA gyrase, topoisomerase, DNA ligase, and DNA polymerase
-1.) Topoisomerase and gyrase relax the supercoiling of the strands
-2.)Helicase unwinds and
separates the strands in
small segments
-3.)A replication fork is
created
-4.)DNA polymerase joins nucleotides to the growing DNA strand
-In the 5' ? 3' direction
What is semiconservative replication?
each new double-stranded DNA molecule contains one original (conserved) strand and one new strand
Describe protein synthesis, from transcription to translation
PROCESS OF TRANSCRIPTION
-Transcription: of DNASynthesis of a complementary mRNA strand from a DNA template; copies a particular segment
-Requires RNA polymerase and RNA nucleotides (AUGC)
-Transcription begins when RNA polymerase binds to the promoter se
What is the role of the promoter, terminator, and mRNA in transcription?
PROMOTER
-segment of DNA where RNA polymerase initiates transcription of structural genes
TERMINATOR
-where transcription stops
mRNA
-temporary copy of the gene that will go to ribosome for translation
1.) How does mRNA production in eukaryotes differ from the process in prokaryotes?
2.) Why can translation begin before transcription is complete in prokaryotes but not in eukaryotes?
1.)
In Eukaryotes
-Exons are regions of DNA that code for proteins
-Introns are regions of DNA that do not code for proteins
-Introns need to be removed
2.)
-In eukaryotes, transcription occurs in the nucleus, whereas translation occurs in the cytoplasm
-
What is an operon?
A set of operator and promoter sites and the structural genes they control; genes are transcribed together and normally have related functions
How is gene expression regulated in bacteria by induction, repression, and catabolite repression?
Induction
-where gene expression is normally off, and we want to turn it on
-how it happens: when gene expression is off, repressor will bind to operator (off). To turn gene expression on, inducer will bind to repressor, thus the repressor can no longer b
How does miRNA stop protein synthesis?
-microRNAs (miRNAs) base
pair with mRNA to make it
double-stranded
-Double-stranded RNA is
enzymatically destroyed,
preventing production of a
protein
Classify mutations by type
-Base substitution: a single base (A, T, G, or C) is replaced by a different base
-Silent mutation: Base substitution does not change the amino acid in the protein, due to degeneracy of the genetic code
-Missense mutation: Base substitution results in an
Describe how chemical mutagens and radiation cause mutations
CHEMICAL MUTAGENS
-Nitrous acid: alters the structure of adenine so that it bonds with cytosine instead of thymine
-Nucleoside analog: structurally similar to normal bases but have different base-pairing properties
-Other chemical mutagens cause deletions
Describe two ways mutations can be repaired
UV damage can be repaired:
1.)Photolyases separate thymine dimers (uses light energy)
2.) Nucleotide excision repair: Enzymes cut out incorrect bases and fill in correct bases
Describe the effect of mutagens on the mutation rate
Mutagens increase the mutation rate by a factor of 10 to 1000 times
Outline the methods of positive (direct) and negative (indirect) selection of mutants
Positive (direct) selection detects mutant cells that grow or appear different than unmutated cells
Negative (indirect) selection detects mutant cells that cannot grow or perform a certain function
-negative uses replica plating
What is an auxotroph?
mutant that has a nutritional requirement absent in the parent (mutant is unable to synthesize a growth factor that it needs, so it can only grow if the growth factor is provided in the media)
What is genetic recombination?
exchange of genes between two DNA molecules; creates genetic diversity
Differentiate horizontal and vertical gene transfer
-Horizontal gene transfer: transfer of genes between cells of the same generation
-Vertical gene transfer: transfer of genes from an organism to its offspring
Describe transformation, conjugation, and transduction
TRANSFORMATION
-Genes transferred from one bacterium to another as "naked" DNA
CONJUGATION
-Plasmid transferred from one bacterium (donor) to another (recipient)
-Requires cell-to-cell contact
TRANSDUCTION
-DNA is transferred from a donor cell to a recipi
What are plasmids and transposons?
PLASMIDS
-Plasmids are self-replicating circular pieces of DNA (separate from the chromosome)
TRANSPOSONS
-Transposons are segments of DNA that can move from one region of DNA to another ("jumping genes")