BIO UNIT 6

pyrimidines

single ringed structure

U, C, T

Purines

double-ringed structure

G, T

What has circular chromosomes

Prokaryotes

What has multiple linear chromosomes

Eukaryotes

DNA and in some cases RNA is the primary source of…

Heritable information

Semiconservative DNA replication

each strand of DNA serves as a template strand for the synthesis of the complementary strand

Direction of nucleotides added in replication

Nucleotides are added from the 5’ - 3’ direction

leading strand

strand that is continuously synthesized

lagging strand

strand that is synthesized in fragments

helicase

unwinds DNA

Topoisomerase

relaxes the supercoil at the replication fork

replication fork

where the two strands of DNA are seperated

DNA polymerase

Synthesizes new strands of DNA

Ligase

joins DNA on lagging strand

how to genetic information flow

DNA → RNA → Protein

DNA transcription

DNA unzips and RNA Polymerase synthesizes mRNA in the 5’-3’ direction on the DNA template strand (noncoding strand)

mRNA

carries the genetic information from the DNA to the ribosome

Codon

3 base sequence of nucleotides found on mRNA

anticodon

3 base sequence that attaches to the opposite bases of the codon which results in the addition of an amino acid to the polypeptide chain and the release of the tRNA

rRNA

responsible for protein assembly. anticodon - codon pairing occurs in ribosomes

mRNA transcript in eukaryotes

addition of a poly a tail

additon of GTP cap

introns

sequences of mRNA that don’t code for amino acids

not included in mature mRNA transcript

Exons

sequences of mRNA that do code for amino acids and are connected to each other to make the mature mRNA transcript

alternative splicing

process of splicing (removing introns) and then connecting the remaining exons

exons combinations

different combinations of exons on a transcript encode for different proteins

exons - 1,2,3,4

transcript - 1,2,3 or 1,2,4

Translation

process in which the mRNA is used to generate polypeptides

occurs on ribosomes

translation steps

1. Initiation - start the process of making a polypeptide
2. Elongation - polypeptide grows
3. termination - stop the process and the polypeptide is cut off

Retrovirus

introduce viral RNA into the host cell and goes from RNA to DNA where the DNA is then transcribed and translated

Initiation

rRNA interacts with mRNA at the first start codon (AUG)

Elongation

tRNA brings another amino acid which gets added to the polypeptide chain

Termination

when a tRNA brings an amino acid sequence for a stop codon the polypeptide is released

Gene expression

the process by which instructions in the DNA are transcribed and translated into a functional protein

regulatory sequences

stretches of DNA that can be used to promote or inhibit protein synthesis

transcription factors

proteins that promote or inhibit transcription of a gene

Inducible

is inhibiting until an inducer comes and removes it

EX - lac operon.

* inhibits the breakdown of lactose until there is a lot of lactose that attaches to the operon and removes it allowing lactose to be broken down

what initiates transcription

interaction between regulatory proteins, regulatory genes, and transcription factors

negative regulatory molecules

block the RNA poly from attaching to the promoter so transcription cannot occur

mutations

changes of a genome in an organism

can be positive, negative, or neutral

primary source of genetic variation

substitution mutation

switching a nucleotide with another

EX - ACG changes to ACA

deletion mutation

deleting a nucleotide

EX - ACG changes to AC_

insertion mutation

adding a new nucleotide

EX - ACG changes to ACGC

triploidy

having 3 copies a particular chromosome

polyploidy

having multiple sets of homologous chromosomes

electrophoresis

DNA is negatively charged and is loaded into the gel.

smaller fragments move faster and further towards the positive side while bigger fragments move slower and shorter

polymerase chain reaction

Copies a small amount of DNA into a lot of DNA