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The Nature of the Gene, Alleles, and Mutation

Todays questions: At the molecular level, what is a gene? An allele? A mutation?

I. The molecular nature of the geneII. The central dogma of molecular biologyIII. The molecular nature of mutation

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The current definition of the ene: -We're not reallysure.-Genes are made ofDNA.-"Blueprint oflife".-A chromosome isone long DNAmolecule.

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T A C A C A C A C C G G C T A A C G A C C A T A C G A G

(a chromosome is one long DNA molecule, wrapped around proteins)

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. building block of a protein

A T G T G T G T G G C C G T A T G C T G G T A T G C T CT A C A C A C A C C G G C T A A C G A C C A T A C G A G

Start Cysteine Valine Alanine Aspartic acid

Cysteine Trypto phan

Tyrosine Alanine

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What do we know about genes?

. products that function in the cell

4. as well as regulatory regions (involved in turning genes on off u or down

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The importance of regulatory sequences: 1. Muscle cells and nerve cells contain the same

c romosomes. y are e ce s so eren

2. Dr. Freeman has the genes required to make a uterus. Why doesnt he have one?

3. In many cases, t e proteins pro uce y omo ogous genes in chimps and humans are identical or nearly

.

Same genes (and regulatory regions). But the regulatory regions regulate whatgenes are expressed and what aren't.

Because of male-specificregulatory factors.

Key change in regulatory

regions.

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DNA

siRNA,tRNA,rRNA, snRNA,

mRNA

et al.

Protein, ,

receptors, motors,pumps, channels etc.)

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Genes DNA represent the genotype

Proteins and RNAs (gene products) represent the

phenotype

. , color?

2. At the molecular level what is an allele?

Coding + regulatory regions in DNAwith a gene.

Different in basesequences.

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3. What happens to the genotype and phenotype if there is a change in the sequence of bases in the coding region of a gene?

. is a change in the sequence of bases in the regulatory re ions of a ene?

There will be a change in both the genotype(changes for sure)and phenotype (if the pointmutation isn't silent).

Genotype will change. But now a gene can be expressed more or less,leading to changes in a phenotype.

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A. When chromosomes replicate, DNA is copied by

enzymes. , .

1. What are the consequences of these mistakes, for the genotype?

Changes the base sequence which changes the allele.

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2. Many copying errors change the DNA base sequence, and also change the RNA or protein product.

How do these errors affect the phenotype?

Do these errors create alleles?

Mutation is change in DNA sequence.

The mutation changes the product (mRNA), the protein created may change whichmeans that the phenotype might change.

Yes, they can create a new version of a gene, or an allele.

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3. Some copying errors change the DNA base sequence, but do NOT change the protein product.

How do these errors affect the phenotype?

Do these errors create alleles?

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B. Mistakes in meiosis can lead to a doubling of the number of chromosomes or other changes in

. . .

Do these errors affect the enot e?

Do these errors affect the phenotype?

Yes, because there are now more genes.

Usually, like 21st extra chromosome is equal to Down Syndrome.

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Key definition (from the reading quiz): mutat on s any c ange n an organ sm s .

characters) work?

It doesn't change the DNA.