Chapter 8 - DNA Structure and Function By: Ryan Bihasa-Lenahan

DNA Strand

Background

- DNA is a polymer of nucleotides, each with a five-carbon sugar, three phosphate groups, and one of four nitrogen-containing bases

Watson and Crick

Watson & Crick

- English researchers that suspected the DNA is a helix - proved this by connecting scraps of metal at suitably angled "bonds" of wire

Chargaff

Erwin Chargaff Rules

- Austrian biochemist who uncovered additional detail of DNA structure

- First Rule - the amounts of thymine and adenine are identical as are the amounts of cytosine and guanine (A=T, G=C)

- Second Rule - DNA of different species differ in its proportions of adenine and guanine

Base Pairs

How do the base pairs bind?

-Base pairs are bind with hydrogen bonds that bind internally positioned bases holding the two strands together

-There are two types of base pairings but four different ways to pair the map

— AT

— TA

— CG

— GC

Chromosome

What is a chromosome?

- A chromosome is a structure that consists of DNA and associated proteins

— carry parts or all of the cell's genetic information

- Chromosomes are duplicated in DNA replication

- Each species has its own chromosome number (number of chromosomes in its cell)

- Human cells have two sets of 23 chromosomes - 2 of each type

- There are also chromosomes that are the same in males and females which are autosomes

Human Male Karotypes

What is a karyotypes?

-It is the number of the visual appearance of the chromosomes in the cell nuclei of an organism or species

— in other words, An image of an individual's diploid set of chromosomes

The Process of DNA Replication

How does DNA replicate? (This should be in depth)

- A cell copies its DNA in the process of DNA Replication

- The process takes place in a chromosome that consists of one molecule of DNA (one double helix)

- When the process begins, enzymes begin to break away the hydrogen bonds that hold the double helix together - the DNA strands unwind and separate

- Another enzyme begins to construct primers - short, single strands of nucleotides

— they serve as attachment points for DNA polymerase, the enzyme that assembles new strands of DNA

— a primer base-pairs with a complementary strand of DNA

- The process of nuclei acid hybridization occurs - DNA polymerases attach to the hybridized primers and begin DNA synthesis

- The enzyme DNA ligase seals any gaps, therefore the new DNA strands are continuous

- Both strands of the parent molecule are copied at the same time

- As the DNA strand lengthens it winds up with its template strand into a double helix

- two copies of a DNA molecule are produced in semiconservative replication - one strand is new, the other is parental

Causes of DNA Damage

What damages DNA?

- DNA damage is the alteration of the chemical structure of DNA like a break in the strand, chemically changed or missing bases or nucleotide getting lost or slipping out.

- Some of these mistakes can occur when DNA polymerases work very fast in DNA replication

- When damaged DNA begins to replicate there may be errors which lead to mutations

- mutations are permanent change in the cell's DNA sequence

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