Flashcards in Lecture 8 Deck (86):
science of heredity
science of dealing with DNA and protein synthesis
total DNA contained within the cell, consists of chromosomes and any plasmids present
Genes are contained on ..
sections of DNA that code for a functional product
DNA is the..
macromolecule which is composed of nucleotides
Nucleotides of DNA are composed of
4 types of nitrogenous bases in DNA
used to located the carbon on the pentose sugar
two strands of DNA are held together by H bonds in between bases
Hydrogen bonds always occur in between..
specific bases, known as base pairing
Adenine pairs with.. via..
thymine; 2 hydrogen bonds
Guanine pairs with... via
cytosine; 3 hydrogen bonds (more H bonds in bacteria who withstand more heat, harder to break)
Strands of DNA are..
complementary to one another
The sequence of one strand (parent strand) determines
sequence of another. (ex: 5’ACTGATT3’
The adjacent nucleotides are linked together by...
covalent phosphodiester bonds (sugar phosphate backbone)
Carbon #5 of one nucleotide is joined to..
carbon #3 of the next nucleotides
DNA is referred to as occurring..
from 5' to 3'
Flow of genetic information
-DNA replicates before division so that each offspring receives one complete copy of genome
-DNA is used within the cell to make proteins
-DNA can flow between 2 diff bacterial cells (recombination)
one parental double stranded DNA molecule is used to make 2 identical double stranded DNA molecules
Since the DNA strands in DNA replication are complementary...
one strand of DNA can serve as a template for synthesis of other strand.
small segment of sDNA unwinds and strand separate
Each separated strand serves as..
a template for synthesis of a complimentary strand
What enzymes are responsible for unwinding and separating the two DNA strands
DNA gyrase and helicase (first step)
is found only in bacteria and NOT in eukaryotic cells therefore it serves as an antibiotic target
pulls the strand aport making it not its helix
A short RNA primer is synthesized by the enzyme..
The primer serves as an..
attachment point for new nucleotides in order to form the new strand of DNA (second step)
DNA synthesis occurs by the enzyme ..
DNA polymerase (third step)
Nucleotides are placed..
in the correct order based on the sequence of the parent strand
links the nucleotides together with phosphodiester bonds
What type of bonds form in between new strand of parent strand linking them together
DNA polymerase can only add nucleotides in..
one direction, 5' to 3' and template must be read in 3' to 5'
Synthesis of the first stand is..
continuous and known as leading strand
Synthesis of the second strand is..
discontinuous and is known as the lagging strand
Lagging strand synthesis
slower and more laborious than leading strand synthesis, must be made in the 3' to 5' direction
DNA polymerase synthesized small fragments of DNA called..
okazaki fragments (made in 5' to 3' direction)
Okazaki fragments are joined together by..
the enzyme DNA ligase
In RNA what is different than DNA
ribose not deoxyribose and uracil not thymine
synthesis of a complementary strand of RNA from a DNA template
3 types of RNA
-messenger RNA (mRNA)
-ribosomal RNA (rRNA)
-transfer RNA (tRNA)
carry the coded info for making specific proteins, will directly form protein synthesis
form part of ribosomes which are where protein synthesis occurs. gets put into pieces of a protein, once assembled won't go on and become a protein
carry specific AA tot he ribosomes in order to make proteins. shuttle for AA, never turns into a protein
-enzyme: RNA polymerase
-a supply of RNA nucleotides
-a DNA template
Steps in transcription
1. RNA polymerase binds to DNA at a specific site-promoter
2. RNA polymerase assembles nucleotides into a new RNA chain
3. RNA polymerase moves along templater as the new RNA chain grows
4. RNA polymerase reaches the end of the gene-terminator
5. RNA polymerase and newly formed single stranded RNA are released
Purpose of transcription
mRNA serves as a short term copy of the gene that can be used to direct protein synthesis, rRNA and tRNA assist with the process of protein synthesis
information in mRNA is translated in order to make proteins (codons)
info from mRNA which is a group of 3 nucleotides
Each codon is containing 3 nucleotides specifies a..
certain amino acid
How many codons? how many stop codons>
64 codons, 3 stop codons
Amino acids are..
redundant, while there are more than one way you can create an amino acid
is cloverleaf shape with anticodon of the tRNA
What codons are the stop codons (nonsense codons)
UAG, UAA, UGA. signal end of translation
1. mRNA attached to the ribosome
2. tRNA carrying the correct amino acid enters the ribosome and binds to the mRNA
3. the next tRNA with the amino acid enters the ribosome and binds to the mRNA (e site=exit)
4. 2 amino acids are joined by a peptide bond
5. ribosome moves down mRNA 5’to 3’ direction and and steps 3-4 are repeated until a stop codon is reached
6. mRNA and protein are released from the ribosome
change in the nucleotide sequence of DNA, this change may cause a change in a protein encoded by a gene
Types of mutation
substitution, a single nucleotide is replaced by another nucleotide
When DNA replicates is results in..
a substitution base pair
when DNA is transcribed and translated, an incorrect base can result in an incorrect aa in the protein
2 frameshift mutations
additional nucleotide is added
nucleotide is removed
change the reading frame of the mRNA, sequence of most of the protein is changed downstream from the mutation
stop codons may also be introduced prematurely as a result leading to short proteins
2 ways mutations occur
-mutations due to mutagens
occur due to occasional mistakes during DNA replication, occur in absence of mutagens
Mutations due to mutagens
occur because of agents which work to bring about mutations in DNA (UV light, radiation)
Regardless of the origin, mutations can result in..
-impomlete truncated proteins which are usually non functional
-protein with a diff sequence which will then have either a diff function or normal function
-silent mutation which has no effect on the protein (functional protein)
self-replicating double stranded DNA molecules, contain genes which are non-essential such as those encoding resistance to penicillin
F-factor or fertility plasmid, carry genes to make F pili, involved in bacterial mating
F pili also allows for the..
transfer of genetic material in between
resistance factors, carry genes for antibiotic resistance
virulence factors, carry genes for toxin production, ability to cause diseases
Horizontal gene transfer
DNA is transferred to other bacterial cells rather than to progeny
this is uptake of naked DNA pieces by a bacterial cell, DNA can come from dead cels or from released plasmids
pieces can be integrated into the chromosome
bacterial mating, F plus allows the attachment of the F+ cell to the F- cell
Male cell for conjugation
has an F pili referred to as F+ donor
Female cell conjugation
does not have an F pili and is referred to as F- recipient
A copy of the F plasmid can be..
passed through a hollow tube to the F- cell
F- recipient cell now becomes..
an F+ cell
small fragments of DNA are transferred in between bacteria by a virus (bacteriophages)
viruses that infect bacteria
Steps in tranduction
-phage attached tot he bacterial cell wall and injects its DNA into the cell
-phage DNA is replicated within the bacterial cell
-phage DNA directs protein synthesis in order to make new phage
-new phages are assembled
-the "accident" phage can infect another bacterial cell
-DNA can now be incorporated into bacterial chromosome