Biology Exam 3, Chapter 11

DNA’s full name

Deoxyribonucleic acid

DNA

The genetic material, blueprint, that provide instruction on how to produce an individual’s traits.

Information

The first of genetic instruction criteria; to be genetic material, it must contain the full set of instructions necessary for the entire organism. (The new desk’s instructions)

Replication

The second of genetic instruction criteria, to be genetic material, it must be able to be accurately copied. (The instructions for the desk are legible, in order, and able to be followed)

Transmission

The third criteria for genetic instruction, to be genetic material, it must be able to be passed down from parent to offspring.

Variation

The fourth criteria for genetic instruction, to be genetic material, differences in the genetic material must account for both differences within the species and among other species. (different desks have different sets of instructions)

Nucleotides

What DNA is made up of, also called the building blocks of DNA.

Phosphate group, 5-carbon pentose sugar called deoxyribose, and a nitrogenous base

What DNA nucleotides are made up of…

Phosphate group, ribose sugar, and a nitrogenous base subbing out Thymine for Uracil.

What RNA nucleotides are made up of…

DNA Strand

Nucleotides covalently bonded to each other, producing a string

Double Helix

Two strands that are hydrogen bound to each other and twisted for form a helix or staircase structure.

Chromosomes

A single, continuous DNA double helix wrapped tightly around support proteins and folded into a compact structure. They package, protect, organize, and distribute genetic material so cells can grow, replicate, and transmit.

Genome

A organism’s complete set of instructions.

Erwin Chargaff

Credited for finding that the amount of Adenine (A) is equal to Thymine (T) and the amount of Guanine (G) is equal to Cytosine (C). His findings are called Chargaff’s rules or the AT/GC rule.

Nitrogenous bases

Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)

AT and GC percentages in human DNA

30.3% and 19.5/19.9%

Roselind Franklin

Used X-Ray diffraction to find initial evidence of DNA’s helical shape.

Watson and Crick

Used known data and previous experiments to make a model of the DNA’s helical structure by putting cardboard nucleotides together like a puzzle. They didn’t perform an experiment, but rather had the smarts to put all the information together.

Backbone of DNA (or RNA)

Phosphate group and sugar. (The sides or rails of the ladder, always outside the structure)

Pairs of nitrogenous bases

One base from each strand oppose each other to make the rungs or steps of the ladder, always inside the structure.

Directionality

The single strand of DNA has a distinct head and tail, marked by a 5’ or 3’ on the sugar ring.

5 prime

A phosphate group is attached to the 5th carbon of the sugar ring.

3 prime

An open hydroxyl group (-OH) is attached to the 3rd carbon of the sugar ring.

Where do you start counting the sugar molecules on the ring?

The first molecule starts on the right side below the O.

Complementary strands

The bases are paired in specific combinations due to the AT/GC rule. Adenine from one strand hydrogen bonds to Thymine from the other and Guanine hydrogen bonds to Cytosine.

Antiparallel strands

The two strands run in opposite directions. One runs 5’ to 3’ and the complementary strand runs 3’ to 5’.

Simplistic overview of DNA Replication

Two parental strands of DNA separate and act as a template. Nucleotides use the template and base pairing rules to line up and join together via covalent bonds. A new complementary daughter strand is formed. More than a dozen enzymes and proteins catalyze/participate.

semiconservative mechanism of replication

The daughter molecules have one old strand and one newly made strand at the end of replication.

Dehydration reactions

How covalent bonds are formed

Daughter molecule

The complete double helix formed at the end of replication

Identifying an enzyme

If it ends in -ase, it’s an enzyme

Separation of the two strands

The first event, happens at multiple different sites through denaturation. DNA helicase separates the strands and DNA topoisomerase prevents knots.

DNA single-strand binding proteins

Special proteins bind to the separated strands and form a blockade preventing them from joining back together because the two strands are like magnets and want to reconnect even after separation.

DNA Polymerase

The enzyme that catalyzes the elongation of new DNA. It synthesizes new DNA by reading an existing strand of DNA and building a matching, twin strand.

Two properties of DNA Polymerase making strands

Cannot start a new strand from scratch and starting a new strand requires a primer.

Primer

Made from primase, short, complementary segment of RNA, which allows DNA polymerase to add DNA to a new strand, 10-12 nucleotides long.

After the formation of a primer

DNA polymerase can add DNA nucleotides to the 3’ prime end, making the new strand ‘5-’3 so the antiparallel property continues. Another type of DNA polymerase later removes the primer and replaces them with DNA nucleotides complementary to the template strand.

DNA Ligase

Last part of DNA replication, glues segments together to close gaps and make one big single replicated strand.

DNA Polymerase proof reading ability

DNA polymerase can check and correct each new nucleotide when it’s added, but it cannot go back and change mistakes later.