Module 4 Test Prep

Gene Expression

take DNA and create a protein from it

-regulated at every level

What places can gene expression be regulated?

Eukaryotic gene expression is regulated during transcription, which happens in the nucleus, and during translation, which happens in the cytoplasm

Do all cells in your body have the same DNA? How does that work?

Yes!

Your eyes have the DNA to make hair but they don’t, because part of the DNA is turned off

What are the molecules DNA is wrapped around?

Histones

How can DNA be turned off?

-Tying histones together keeps them inaccessible

-DNA methylation makes DNA inaccessible

DNA Methylation? Ex.?

Transfer of a methyl group to DNA

-When a woman has 3 X chromosomes, one of them is deactivated by a methyl group being added, and it becomes a Barr body

How is DNA made accessible?

By modifying the histones to be separated

Can DNA be unwound?

Only when it is accessible.

What happens when DNA is unwound?

RNA is made using DNA as a template

What is RNA

ribonucleic acid

-composed of nitrogenous bases Adenine, Uracil, Guanine, and Cytosine

There are many different kinds

Transcription

Process where DNA is copied into RNA

Translation

Process where RNA is used to create proteins

What types of RNA are involved during translation?

Ribosomal RNA- makes up much of the ribosome

Transport RNA- transports the amino acids to the ribosome

Messenger RNA- carries instructions for putting together chains of amino acids (proteins)

How many types of tRNA are there? Does tRNA have codons?

61

tRNA does not have codons like mRNA

-it has anticodons

Codons

Mrna is divided into units of 3 called codons

-codons code for a specific amino acid

What is the START codon? how many stop codons?

AUG for methionine is the start codon

There are three stop codons

How many amino acids only have one codon? What is the max number of codons amino acids have?

Two amino acids only have one codon.

The max number of codons amino acids have is 6

How is mRNA destroyed once it is no longer needed?

RNAi destroys RNA

-mRNA will continue to create polypeptides, but once a satisfactory amount is produced, it needs to be stopped or there can be consequences

Many proteins are only needed for a short time. How are proteins removed once they are no longer needed?

The protein is tagged with ubiquitin and taken apart

Genome

the complete set of genes present in a cell or organism

Mutation

Change in DNA sequence

Somatic mutation

Occurs after conception…therefore not passed onto children

Point Mutation

single base pair is added, deleted, or changed.

-ex: transition or transversion

Occurs at a single “point”

Transition

Point mutation where a purine is turned into another purine (A to G)

or a pyrimidine is turned into another pyrimidine (C to T)

Transversion

Point mutation purine is turned into a pyrimidine

ex: A turned to anything but G

-C turned to anything but T

Nonsense mutation

Point mutation that results in a nonsense codon (premature termination)

Silent mutation

Point mutation that does not change the amino acid, even though the codon has changed

Frameshift Mutation

The insertion or deletion of a nucleotide base

Missense mutation

Results in a different amino acid being encoded…may change the function of the protein

Deletion

Loss of one or more nucleotides…entirely removed instead of replaced

Duplication

DNA segment is copied…results in extra copies of chromosome

Inversion

When dna segment breaks away and reattaches in a reversed order

Translocation

DNA segment breaks off and attaches to another chromosome

Gene therapy

Treats or prevent disease by correcting the genetic issue

-viruses with a lysogenic cycle insert DNA

What is the issue with gene therapy?

modified viruses insert DNA, though sometimes the viruses interrupt other genes when inserting the DNA

How do you analyze DNA?

To do this DNA must be chopped into pieces with restriction enzymes

Gel electrophoresis

Process where DNA is separated and analyzed

How is DNA moved during Gel electrophoresis?

DNA is negatively charge, so when an electric current is applied to DNA it moves towards the positively charged electrode

STR

short tandem repeated DNA sequences

Who inherits STRs?

Males inherit STRs on the Y chromosome from their fathers

LAC operon

inactivates the repressor

TRP operon

activates repressor

Pharming

genetically modifying plants and animals so that they produce a desired substance to be used as pharmaceuticals

Offers promised for Parkinson’s disease

Stem Cell Research

Viruses with a ____ cycle destroy their host cell

Lytic cycle

HIV contains

Single stranded RNA that acts as a template for DNA synthesis

Glow in the dark kittens

GMOs

About ___% of DNA is composed of introns

5%

How are you going to do on this exam?

GREAT