What is DNA and how does it work?

Warm Up Question

• If one parent is Heterozygous for the trait of brown eyes, and the other parent has blue eyes, what is the probability that their child will also have blue eyes? Explain how you came to your conclusion.

• https://www.youtube.com/watch?v=ckZEds5taX4

Unraveling DNA • The structure of DNA allows DNA to hold information. The order of the

bases on one side of the molecule is a code that carries information. • A gene consists of a string of nucleotieds that give the cell information

about how to make a special trait.

• There is an enourmous amount of DNA, so there can be a large variety of genes.

How to read DNA

• DNA code is read like a book, from one end to the other and in one direction.

• The bases form the alphabet of the code.

Nucleotides• DNA is made of subunits called nucleotides,

which consists of a sugar, a phosphate, and a base.

• Nucleotides are identical except for their base, which all have a different shape.

• There are Four Bases.– Adenine (A)– Thymine (T)– Guanine (G)– Cytosine (C)

Copies of DNA• DNA is copied every time a cell

divides. Each cell gets a complete copy of all the DNA.

• During Replication, DNA splits down the middle, and the base for each side of the strand are used as a pattern for a new strand.

• Sometimes, when the DNA is being copied, things can go wrong. This can cause mutations.

Mutations• Sometimes, when DNA is being

copied, things don’t go according to plan.

• Changes in the number, type, or order of bases on a piece of DNA are known as mutations.

• Mutations can have three outcomes; an improved trait, no change, or a harmful trait.

• Cells make some proteins that can detect errors in DNA, and these can sometimes correct errors. However, if they aren’t repaired, these mistakes become part of the genetic message.

https://www.brainpop.com/health/geneticsgrowthanddevelopment/geneticmutations/

Types of Mutations • Substitution – This is the most

common change, and happens when the wrong bases is used. Sickle cell disease is caused by a substitution, and negativly affects red blood cells.

• Insertion – Sometimes an extra base is added, this is known as insertion.

• Deletion – Sometimes, a base is left out. This is known as deletion.

https://www.youtube.com/watch?v=ZSpFVPBEeLk

How do mutations happen?• Mutations happen most

often from random errors when DNA is copied.

• Damage can also happen when abnormal things happen to your cells.

• Any physical or chemical agent that can cause a mutation to your DNA is called a mutagen.

• Examples of mutagens are radiation, asbestos, and chemicals in ciggerete smoke.