Lecture 2: DNA Structure and Function

What causes of phenotypes (mutations)

Have shown laws of segregation (Mendel) —> shown in many organisms

Chemical analysis of proteins

Shows there are linear chains of amino acids which fold to make shape to do its functions, shape, and abilities

• confirmed that order of Amino Acids determines its shape and abilities

Genetic Material Must

Be able to store a lot of info

Must be a complex molecule

Must duplicate faithfully

Also charge and mutate sometimes

Nucleus and chromosome can be…

• stained (it means scientists could add certain dyes to cells, and the nucleus/chromosomes would absorb or bind the dye and become visible under a microscope.)

Where do chromosomes migrate to when a new cell is formed

To the daughter cell

Nuclei fuse during…

Fertilization

DNA is needed for transformation to occur 

Nucleic acids must be what allows phenotypic transformation (DNA going to cell)

Nucleotide

Composed of a sugar (deoxyribose), a base, and a phosphate group

Do organisms have different organizations of…

nucleotides, yes

4 Bases

Adenine, Guanince, Cytosine, Thymine

Purine

Adenine and Guanine

Pyrimidine

Cytosine and Thymine

Higher GC content —> more hydrogen bonds —>

DNA Strands harder to separate —> higher melting temp

X-ray crystollography of DNA

revealed a 3D structure, helical, phosphates lay outside as 2 chains

DNA strands are…

complementary and replication is possible

Phosphates make DNA…

NEGATIVELY charged

Sickle cell disease

Confirms relationship between DNA and PTN linear formation. Single change in the amino acids is sufficient to change the folding so that they begin to clump and form chains

Central Dogma

Sequence of nucleotides determine the sequence of AA’s in Proteins, which leads to the phenotype

Eukaryotes

Have the real nucleus with membrane separating (genome in linear pieces, chromosomes). Single and multicelled organisms, Mitochondria and Chloroplast

Prokaryotes

Evolved before nucleus (single circular DNA, plasmids). DNA stored in cytoplasm

Nucleus protects outside, making…

transporting info more difficult.

• nuclear membrane protects DNA from processes occurring in the cytoplasm. But having DNA enclosed inside the nucleus makes transporting genetic info more complicated. DNA stays in nucleus, so info is carried out as RNA through nuclear pores.

Where else is DNA found

Mitochondria and Chloroplasts

Plasmids

Also separate DNA molecules, common in bacteria

Endosymbiotic Theory

Mitochondria and chloroplasts originated from formerly free-living bacteria, which helps explain why they retain their own DNA.

Genome

Full hereditary info for organisms —> complete DNA set