True or False

The 'information' part of DNA is in the backbone

False

Rather it is the nucleotides in between the backbone

True or False

The DNA bases consist of Thymine, Cytosine, Guanosine and Uracil

False

The DNA bases are Thymine, Cytosine, Guanosine and Adenine.

Uracil is only found in RNA

A is complementary to T 

(I always think of AT&T, just helps me remember that they go together)

C is complementary to G

They are complementary because the positive and negative charges on their structures line up, allowing them to form H bonds. 

How much of DNA is actually made up of genes

What does the rest of DNA do?

Only 3% of DNA is genes,

the rest have structural function or are regulatory regions. A lot of DNA has unknown function

Structural

Enzymes

Tyrosinase is an enzymes that converts Tyrosine (colorless) into DOPA (colorless).

DOPA spontaneously oxidizes to melanin which is a brown color

T/F

A change in DNA nucleotide sequence always affects the resulting protein conformation.

False

Some amino acids have more than one codon that codes for them. If the change in sequence results in another codon that codes for the same amino acid, there will be no change in protein conformation.

eg. both GCA and GCG code for Alanine

DNA is double stranded and contains A,C G, T

RNA is single stranded and contains A,C,G and U (instead of thymine)

Transcription

Translation

1. RNA polymerase separates the 2 strands of DNA

2. RNA polymerase binds to a promoter and adds complementary base pairs to the template DNA strand

3. The RNA is displaced and the 2 strands of DNA resume their original conformation. 

4. the RNA strand is processed by removal of introns and splicing of exons => mature mRNA

AUG

also codes for methionine

Ribosomal RNA-->rRNA

and proteins

tRNA=transfer RNA

They bring amino acids to the ribosomes

They have an 'anticodon' that is complementary to the codon for the amino acid, this antiocodon forms 3 base pairs with a codon in mRNA.

On the other end it has the amino acid attachment site, the amino acid here corresponds to the anticodon sequence. 

1. A place for translation to occur

2. Enzymatic activity

What enzyme catalyzes DNA replication?

What enzyme catalyzes DNA transcription?

1. To identify all of the genes in the human genome

2. Determine the sequence of the entire human genome

3. Store this information in databases

4. Improve tools for data analysis

5. Transfer related technologies to the private sector

6. Address any ethical, legal and social issues that may arise from the project

What type of genetic inheritance is associated with albinism?

What enzyme is involved in this disorder?

Autosomal Recessive Inheritance

A mutation in the tyrosinase gene results in albinism

1. Trait often skips a generation

2. Two unaffected parents can have an affected offspring

3. Two affected parents CANNOT have a UNAFFECTED offspring

T/F

In an autosomal dominant genetic disorder (like Huntingtons) the mutation often produces a protein that has an altered function, rather than a non-functional protein

T/F

1. Traits do not skip a generation

2. Two unaffected parents cannot have an affected offspring

3. Offspring of one affected parent have a 50% chance of being affected. 

Mr. Robertson has uber hairy ears because of a gene on his Y-chromosome. He is worried that his baby girl is going to have to live with terribly embarassing hairy ears as well.

Explain whether or not Mr. Robertson's concern is necessary.

Should Mr. Robertson worry about whether or not any future sons will have hairy ear?

Mr. Robertson need not worry. If the gene for hairy ears is on his Y chromosome, he will only be giving his X chromosome to his daughter so there is no way for her to inherit that gene.

All of Mr. Robertsons sons will inherit his Y chromosome, thus they will indeed have hairy ears as well.

1. More males than females are affected

2. Daughters can only be affected if their fathers are affected.

3. Males do not pass the trait on to their sons

X-linked Dominant Inheritance

1.Every daugther of an affected father will be affected.

2. Females are more likely to be affected than males, however those males who are affected have more severe cases. 

3. The trait is never passed from father to son

Inactivation of one X chromosome in each cell, this inactivation is random and produces 'bar bodies'

These inactivated cells still divide

Incomplete penetrance describes the situation where an individual carries the genes for the trait but does not express it. 

ie. the phenotype is expressed in only a portion of the population with the genotype. 

The same genotype produces different phenotypes

This can result in someone not being recognized as 'affected' and the pedigree is incomplete

Which 3 modes of inheritance do not fall under the category of Mendelian Inheritance?

1. Incomplete Penetrance

2. Variable Expressivity

3. Mitochondrial Inheritance

Mitochondria carry their own single copy of circular DNA

Egg cells carry maternal mitochondria and the offspring inherits the DNA. 

Thus  mitochondrial inheritance is only through the mother. 

A mutation in the mitochondrial electron transport chain proteins results in reduced ATP synthesis. Cells of the eye have a high ATP demand and they are affected first by this mutation.

The lack of ATP causes some neurons to die and eventually leads to blindness. 

Aneuploidy is a incorrect number of 'sets' of chromosomes.

Haploid and Triploid-->incompatible with life

Have XXY, an extra X chromosome

This is somewhat common and is a popular cause for male infertility.

Only in extreme cases do individuals exhibit female characteristics

Autosomal monosomies are always lethal 

Most autosomal trisomies are also lethal, but not all!

Trisomy 13 (Patau's syndrome)

Trisomy 18 (Edwards)

Trisomy 21 (Downs)

Both Trisomy 13 and 18 are usually lethal before the first year of life.

Majority of Trisomy 21 individuals live past the first year. 

The genetic make-up of all the cells in an individual are not the same. 

Caused by nondisjunction, the later it happens in development the less of an effect it has. 

SNP=single nucleotide polymorphism

A SNP is a mutation that occurs in more than 1% of the population. 

Any less than that and it is simply a mutation

The DMD gene is one of the largest genes, much much bigger than most genes.

The more replication occuring the more chance there if for mutation, and large genes require a lot of replication. 

Methylation occurs on cytosines that are next to guanosine. 

If spontaneous deamination occurs on the methylated cytosine it becomes thymine. 

This thymine is a normal base pair and it's mismatch may not be noticed by DNA repair machinery.

1. Oncogenes that when mutated or over-expressed convert a normal cell to a cancer cell

2. Tumor suppressor genes-when inactivated they allow cells to grow uncontrolled. 

The Ras gene is part of the cascade pathway the initiates replication when a cell is stimulated by growth factor.

If Ras gets mutated, it will be turned on all the time and will constantly cause cell division regardless of whether or not signals are being sent. 

p53

1. Suppresses progression through the cell cycle in response to DNA damage

2. induces apoptosis in response to severe stress

3. Transcriptional activator of DNA repair genes

4. Transcriptional activator of genes that inhibit angiogenesis, invasion and metastasis

i. uncontrolled growth

ii. lose contact inhibition

iii. altered cytoskeleton and cell adhesion

iv. altered nuclear shape and organization

v. produce invasion-allowing enzymes

2 Hit Hypothesis

Some people inherit genes that already have one p53 gene knocked out.

They are that much closer to having both p53 genes knocked out than someone who did not inherit this. Thus they have a higher susceptibility

DNA methylation and Histone Modification

Base methylation suppresses gene activity and Histone modification alters the acitvity of the DNA it wraps around.