Genetics, DNA, and Heredity, Lecture notes of Genetics

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Genetics, DNA, and Heredity

The Basics

What Does DNA Look Like?

A

T

C

G

Every cell in our body has the

same DNA….

Eye cell

Lung cell

Toe cell

Karyotype

What makes one cell different from another?

DNA = “the life

instructions of the

cell”

Gene = segment of

DNA that tells the cell how to make a

certain protein.

Allele = one of two

or more different

versions of a gene

Sequence for normal adult hemoglobin:

Sequence for mutant hemoglobin:

Wild-type Hemoglobin Protein

Mutant Protein

Normal Red Blood Cell

Abnormal Red Blood Cell

The HGP: International effort to decipher

the blueprint of a human being.

How It Was Done

DNA samples collected fromthousands of volunteers

Samples sent to Human GenomeProject centers across the world

Scientists at centers perform DNA

sequencing and analysis

February 2001: Draft of thesequence published in Nature(public effort )and Science(Celera – private company).

April, 2003 (50 years afterWatson and Crick structure ofDNA was published) : Fullsequence published andresearchers determined thatwithin this sequence there wassomewhere between 30,000and 40,000 genes. We nowbelieve there are closer to25,000 genes

Still A Lot of Work To Do...

Analyzing

genetic variation

between

individuals and

populations

Discovering

DNA and gene

functions

Investigating

interactions between DNA sequences, gene

products, and

environmental factors

Comparing the

genomes of humans and

other organisms

Inheritance of Genes

Gregor Mendel

1822-1884^ •

Augustinian monk whocross-bred pea plants withdifferent characteristics

Observations led to lawsregarding the transmissionof hereditarycharacteristics fromgeneration to generation

Many of the concepts fromhis observations still holdtrue today!

Picture from www.nih.nlm.gov

Mendel’s

Laws:

2. Principle of Independent Assortment:

Genes for different traits assortindependently of one another in gameteproduction What it means: different genes areinherited separately. For example, thegene which codes for eye color is inheritedseparately from the gene which codes fornose shape.

Mendelian Concepts

Dominant = only one allele of a genenecessary to express the trait Recessive = both alleles of a gene mustbe identical to express the trait Heterozygous = alleles of a particular geneare non-identical Homozygous = alleles of a particular geneare identical