AP Biology UNIT-6

DNA Replication

process of copying DNA

Transformation

A change in genotype and phenotype due to the assimilation of external DNA by a cell.

Transforming Factor

The DNA responsible for bacterial transformation.

Watson and Crick

Developed the double helix model of DNA.

Rosalinda Franklin

X-ray crystallography image of DNA! She discovered the density of DNA and established that molecules existed in ahelical conformation.

revealed the double helix of DNA

Semi Conservative Replication

in each new DNA double helix, one strand is from the original molecule, and one strand is new

Why does adenine bond with thymine?

Adenine, a purine, and thymine, a pyrimidine, bond with each other because they both have two hydrogen bonds

Why does guanine bond with cytosine?

Guanine, a purine, bonds with cytosine, a pyrimidine, because they both have three hydrogen bonds

Purines

Adenine and Guanine

Pyrimidines

Cytosine and Thymine

How is bacterial DNA replication accomplished?

Replisome (helicase, topoisomerases and DNA polymerase III) directs bidirectional DNA replication from a single origin of replication.

Prokaryotes

No membrane-bound nucleus

Eukaryotes

contain membrane-bound nucleus and organelles

DNA polymerase

Enzyme that joins individual nucleotides to produce a DNA molecule

DNA is antiparallel

strands run in opposite direction and replication is semiconservative- each strand acts as a parent strand for the new molecules

Leading Strand

synthesized continuously

Lagging Strand

The strand that is synthesized in fragments using individual sections called Okazaki fragments

Okazaki fragments

Small fragments of DNA on the lagging strand during DNA replication, joined later by DNA ligase.

DNA Ligase

enzyme that chemically links DNA fragments together

Primer

a short stretch of RNA with a free 3' end, bound with DNA nucleotides during DNA replication

Helicase

unwinds DNA

Single Stranded Binding Protein

Binds to and stabilizes single-stranded DNA until it can be used as a template.

Topiosomerase

snips away pieces to loosen DNA strands to release tension

Primase

synthesizes RNA primer

DNA polymerase III

- used by prokaryotes

- can synthesize a new strand of DNA

- read template DNA 3' to 5'

- synthesize new strand 5' to 3'

DNA Polymerase I

removes the RNA primer and replaces it with DNA

Telomeres

the ends of chromosomes; their length decreases with each cell duplication.

Telomerase

catalyzes the lengthening of telomeres in germ cells

Nuclease

DNA cutting enzyme

Mismatch Repair

repair enzymes correct errors in base pairing

Bacteria Cell

Lacks nucleus, RNA produced by transcription

Eukaryotic Cells

The cell provides separate area for transcription.

Transcription

synthesis of an RNA molecule from a DNA template

Translation

Process by which mRNA is decoded and a protein is produced

Replication

Copying process by which a cell duplicates its DNA

Template Strand

the strand of DNA that specifies the complementary mRNA molecule

Codon

In mRNA, a nucleotide base triplet that codes for an amino acid or stop signal during translation

Anticodon

a nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on an mRNA molecule

Reading Frame

Reading mRNA nucleotides in the correct groupings.

Prokaryotic Promoter

establishes where RNA synthesis is initiated.

Prokaryotic Termination

Sequence of Nucleotide, marks end of gene, signals to release newly made RNA from DNA

Prokaryotic Termination of Transcription

Proceeds through a termination sequence

Eukaryotic Termination of Transcription

Pre mRNA is cleaved from growing RNA chains while polymerase II continues.

Why is RNA processing necessary?

RNA processing is necessary to protect message and attach to ribosome

mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

RNA splicing

removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence

Introns

Noncoding segments of nucleic acid.

Exons

coding segments of DNA

Splicesome

1) assembled from snRNPs (snurps) and protein complexes

2) enzyme that carries out RNA splicing; |

3) removes introns from a transcribed pre-mRNA (splicing)

snRPS

short nucleic segments at the end of the introns that signal where it will splice.

Ribozymes

catalytic RNA molecules that function as enzymes and can splice RNA

Alternative RNA splicing

Some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during splicing

Mutation

A change in a gene or chromosome.

Point Mutation

gene mutation in which a single base pair in DNA has been changed

Base-Pair Substitution

type of mutation in which a single base pair changes

Missense

a mutation that changes one amino acid

Nonsense

codon changed to a stop codon

Insertions

additions of nucleotide pairs in a gene

Deletion

removals of nucleotide pairs in a gene

Frame-shift Mutation

a mutation involving the addition or loss of nucleotides

Mutagen

A chemical or physical agent that interacts with DNA and causes a mutation.

A summary of transcription and translation in a eukaryotic cell.

Plasmids

Circular DNA molecules that can replicate independently of the main chromosomes of bacteria

Chargaff's Rule

A=T and C=G

Direction DNA is synthesized

5' to 3'

Central Dogma of Biology

DNA -> RNA -> Protein

What type of RNA carries the instructions for making proteins to the ribosome?

mRNA Messenger RNA

What type of RNA carries the anticodon?

tRNA Transfer RNA

What type of RNA makes up ribosomes?

rRNA (ribosomal RNA)

This protects the mRNA molecule from enzymatic degradation in the cytoplasm and aids in transcription termination, export of the mRNA from the nucleus, and translation

Poly-A tail

This is used as a recognition signal for ribosomes to bind to the mRNA. It plays a role in the stability of the mRNA molecule

GTP cap

Excision of introns & splicing and retention of exons can generate different versions of the resulting mRNA molecule. What is this called?

Alternative splicing

The first stage of translation is called

Initiation

The second stage of translation is called

Elongation

The third stage of translation is called

Termination

What causes translation to be initiated?

The mRNA start codon interacts with the rRNA in the ribosome

What forms a polypeptide chain?

Amino acids

Retrovirus

An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.

lac operon

the operon that controls the metabolism of lactose

Tryp operon

Repressible operon

An example of an inducible operon is the

lac operon

This is a small non-coding RNA molecule (containing about 22 nucleotides) found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression

miRNA (microRNA)

These are the primary source of genetic variation

Mutations

What is transformation?

A change in genotype and phenotype due to the assimilation of external DNA by a cell.

What is Transduction?

Viral transmission of genetic information

Conjugation

In bacteria, the direct transfer of DNA between two cells that are temporarily joined.

Gel Electrophoresis

The separation of nucleic acids or proteins, on the basis of their size and electrical charge, by measuring their rate of movement through an electrical field in a gel.

When does it mean when DNA is amplified?

Multiple copies are made of DNA fragments

What is PCR?

Polymerase Chain Reaction; a procedure used to amplify DNA

Viruses that infect bacteria are called

Bacteriophages

What type of bond joins the nitrogenous bases of DNA

Hydrogen

What type of bond joins the phosphate-sugar backbone of DNA

Phosphodiester

What determines RNA function?

Sequence of RNA bases

Structure of the RNA molecule

'Illustration' of DNA replication

What is another name for the antisense strand of DNA?

Noncoding strand

How does RNA know when to stop translation?

When it comes to a stop codon