AP Bio Unit 6

What is the shape of chromosomes in prokaryotes?

Circular

What is the shape of chromosomes in eukaryotes?

Linear

What are chromosomes made of?

DNA coiled around histone proteins

What do both prokaryotes and eukaryotes contain?

Plasmids

What are plasmids?

Circular DNA molecules that are not part of any chromosome

What does DNA replication ensure?

Offspring have genetic information

In what direction are DNA strands produced?

The 5' to 3' direction

What is one trait of DNA replication?

It is semiconservative

What does it mean that DNA replication is semiconservative?

Each DNA molecule is comprised of one new and one old strand

What does helicase do?

Seperate DNA strands

What does topoisomerase do?

Prevents supercoiling and relaxes DNA

What are RNA primers used as?

A starting point for DNA polymerase

What does DNA polymerase do?

Synthesize new nucleotides that match those on the template strand

What is the leading strand?

The strand where replication moves towards the replication fork, and nucleotides are synthesized continuously

What is the lagging strand?

The strand where DNA replication moves away from the replication fork and nucleotides are synthesized in fragments

What are Okazaki fragments?

Short lengths of single-stranded DNA made on the lagging strand

What does ligase do?

Seal Okazaki fragments on the lagging strand together to form continuous strands

What is the central dogma of molecular biology?

DNA -Transcription> RNA -Translation> Protein

What does mRNA do?

Carries a code transcript from DNA to ribosome

What does tRNA do?

Bind to specific amino acids that match with three base pairs in mRNA (codons) during protein synthesis

What is rRNA?

Building block of ribosomes

What is transcription?

Process in which RNA polymerases use a single strand of DNA (a gene) to form a new RNA molecule

What does RNA polymerase do?

Produce the mRNA transcript (pre-mRNA) which is modified before leaving the nucleus (in eukaryotes)

What does 5' GTP cap do in modified pre-mRNA?

Help with ribosomal recognition

What does 3' poly-A tail do in modified pre-mRNA?

Stabilize the mRNA molecule

What does it mean for pre-mRNA to get "spliced"?

The unneeded portions are removed and needed portions are pieced together

What are the unneeded portions of pre-mRNA called?

Introns

What are the needed portions of pre-mRNA called?

Exons

What is alternative splicing?

Different sections of the same mRNA transcript/pre-mRNA can be spliced out and result in different "mature" mRNAs

What does translation involve?

Using mRNA code to make a polypeptide (chain of amino acids) with a ribosome in the cytoplasm or in the rough ER

What does translation occur with in prokaryotes?

Simultaneously with transcription

What are codons?

Groups of three nucleotides that a tRNA molecule binds to in a ribosome

What is the start codon?

AUG, and it triggers the initiation of translation

What does the anticodon do?

Binds with the codon on the mRNA and transfers the corresponding amino acid to the ribosome

What does the stop codon do?

Triggers the release of the amino acid chain from the ribosome, ending translation

What do retroviruses have the ability to do?

Convert RNA into DNA, moving backwards

What do retroviruses use to move RNA backwards?

Reverse transcriptase

After being reversed by retroviruses, what can the new DNA do?

Integrate into the host cells' genome and can be transcribed and translated into new viruses

Aside from the genes an organism has, what else determines an organism's phenotype?

By which genes are expressed, and how much they are expressed

What are transcription factors used for?

Developmental genes in particular sequences of expression, enabling proper development

What are regulatory sequences?

Segments of genes that are not transcribed into mRNA and are used to control what's transcribed/translated

What do regulatory sequences interact with?

Regulatory proteins called transcription factors

What does it mean if a gene is constitutively expressed?

Its always on

What does it mean if a gene is inducible?

It can be turned on by transcription factors

What is epigenetic regulation?

Factors binding to histones, affecting the extent to which DNA is wrapped around, therefore enabling or blocking expression

How are eukaryotic genes expressed?

The same transcription factors (regulons)

How are prokaryotic genes regulated?

Through inducible or repressible operons

What are operons?

Groups of genes expressed and located together

What is the lac operon?

Inducible

What is the trp operon?

Repressible

What is differential gene expression?

Cells express different genes and make different proteins to serve their function

What does differential gene expression result from?

Regulatory processes

What does RNA polymerase bind to?

Promoters

What do transcription factors bind to?

Regulatory sequences upstream or downstream of the promoter

What do positive transcription factors promote?

Transcription and binding of RNA polymerase

What do negative transcription factors bind to?

Genes and they block transcription

What can microRNA (miRNA) do?

Regulate gene expression AFTER transcription by binding to and degrading mRNA's to prevent translation

What are mutations?

Alterations in a DNA sequence that can change the type or amount of a protein produced and the consequent phenotype

What is the ultimate source of genetic variation on Earth?

mutations

What does a change in DNA lead to?

A change in the amino acid sequence of a protein, thereby affecting its shape and its function

What can mutations come from?

Errors in replication, errors in DNA repair, high-energy radiation like UV, reactive chemicals (mutagens)

What is a point mutation?

When one nucleotide is substituted, resulting in a substitution of amino acids

What is a frameshift mutation?

When 1 or 2 nucleotides are added or deleted, altering the 'reading frame' of mRNA codons, altering all amino acids downstream

What is a nonsense mutation?

The alteration of a nucleotide that results in a premature STOP codon

What is a silent mutation?

An alteration in a nucleotide that does not change the resulting amino acid sequence

What determines if a mutation will be beneficial, detrimental, or neutral?

The environment in which an organism lives

How do prokaryotes acquire genes?

Horizontally from other prokaryotes (not by passing them down)

What is transformation in prokaryotes?

Bakteria uptake a plasmid (circular DNA strand) from their environment

What is conjugation in prokaryotes?

Bacteria directly exchange plasmids through a pilus (tube)

What is transposition in prokaryotes?

Movement of segments between DNA molecules

What are the pieces that are moved in transposition called?

Transposons

What is transduction in prokaryotes?

Viruses transfer genes from old host bacteria to new host bacteria; can cause recombination

What are forms of genetic engineering?

Gel electrophoresis, polymerase chain reaction (PCR), bacterial transformation, and DNA sequence

What is used to cut DNA strands into fragments?

Restriction enzymes, which can then be copied, and those fragments can be separated out or integrated into other plasmids

What does gel electrophoresis do?

Separate strands by length by moving fragments through a gel with an electric current

What can the distribution of DNA fragments in gel electrophoresis be used to determine?

If fragments are the same length

What do polymerase chain reactions (PCR) do?

Amplifies DNA replication to produce millions of copies of a target sequence of DNA

What happens in PCR?

DNA is heated to denature/separate strands, then primers are added to the original strand, then a special heat-resistant DNA polymerase extends new DNA strands from the primers (Taq DNA polymerase)

How can bacterial transformation be manipulated?

So that foreign DNA can be incorporated into bacteria

What is DNA sequencing?

Uses DNA's base-pairing rules to determine the sequence of nucleotides in a fragment of DNA

What happens after base-pairing in DNA sequencing?

DNA strands are separated, then treated with fluorescent nucleotides that 'terminate' replication at different lengths