Mr. Malinkovich

OFFICE: Room 321-before school

-by appointment

Honors Biology 2/7/14• Objective: – SBBAT: Describe the structure and function of DNA

- Agenda:- Go over last week’s quiz- Notebook self-check- Take quiz over:

- Meiosis, genetic variation, genetic complexity- Discuss yesterday’s activity- Take notes

- BR: Update TOC: DNA class notes- HW: NONE

Genetic Variation

• Genetic variation among individuals is caused by differences in genes or other DNA segments

• Natural selection can only act on variation with a genetic component (does not act on acquired traits)

• Sources of Variation– Mutations

• Random changes that alters the expression of a trait– Chromosomal rearrangements

• Combinations of chromosomes during gamete formation – Rapid Reproduction

• Quick reproductive cycles = increased chance for mutations– Sexual reproduction

• Mixing of genes from individuals

Genetic Variation

• Mutations can result in favorable traits – Altered continuous or discrete traits

• Increase chance of survival/ reproduction• Increase diversity

• Mutations can result in disease– Decrease chance of survival/ reproduction

• Recombination can– Increase diversity by creating new combinations of existing

alleles– Lead to disease if there are errors in meiosis

• Nondisjunction:

Genetic Complexity

• Sometimes knowing individual’s genotype is not enough to predict phenotype– Complex Traits

• Behavior• Intelligence• Personality

– There is direct evidence that complex traits are affected by genotype and environmental factors• Maze-bright vs maze-dull• Hippocampus development and maternal touch

– involved in memory and spatial navigation

Genetic Complexity

• Sometimes the genotype for a trait involves several genes that are all expressed– Skin color– Incomplete dominance

• Partial expression of dominant allele– Blending of dominant and recessive phenotypes– Sickle cell trait vs disease

– Codominance• Expression of multiple dominant alleles

– Blood types» A, B, AB, O

AA

A

A

TC

G

CG

TG

C

T

Macromolecules: Nucleic Acids• Examples:– RNA (ribonucleic acid)• single helix

– DNA (deoxyribonucleic acid)• double helix

• Structure:– monomers = nucleotides

RNA

DNA

Nucleotides• 3 parts – nitrogen base (C-N ring)– pentose sugar (5C)• ribose in RNA• deoxyribose in DNA

– phosphate (PO4) group

Are nucleic acidscharged molecules?

Nitrogen baseI’m the A,T,C,G or Upart!

Types of nucleotides• 2 types of nucleotides– different nitrogen bases – purines• double ring N base • adenine (A)• guanine (G)

– pyrimidines• single ring N base • cytosine (C)• thymine (T)• uracil (U)

Purine = AGPure silver!

Nucleic polymer• Backbone– sugar to PO4 bond– phosphodiester bond• new base added to sugar of previous

base• polymer grows in one direction

– N bases hang off the sugar-phosphate backbone

Dangling bases?Why is this important?

Pairing of nucleotides• Nucleotides bond between

DNA strands– H bonds– purine :: pyrimidine– A :: T• 2 H bonds

– G :: C• 3 H bonds

Matching bases?Why is this important?

DNA molecule• Double helix– H bonds between bases join

the 2 strands• A :: T• C :: G

H bonds?Why is this important?