hand in lab notebook. the genetics of dog breeds dogs all belong to the same species, but there are...

Hand In Lab Notebook

The Genetics of Dog Breeds• Dogs all belong to the

same species, but there are 350-400 breeds

• Most breeds have only been around for a few hundred years

• What determines dog breeds is controlled by only 50 genes (by contrast human height alone is controlled by over 200 genes)

Human Influence On Dog Breeds

• Human selection of dogs for different tasks (hunting, herding, protection) influenced the expression of these ~50 genes

N1: …G C C C G A C U G AC C C U G G G C A AG C C C C U U G G G G AG G G C U G C U U C G G C C AG …

N2: …G C C C G G C U G AC C C U G G G C A AG C C C C U U G G G G AG G G C U G C U U C G G C C AG …

N3: …G C C C G G U U G AC C C U G G G C A AG C C C C U U G G G G AG G G C U G C U U U G G C C AG …

A1: …G C C C G G C U G AC C C U G G G C A AG C C C C U U A G G G AG G G C U G C U U C G G C C AG …

A2: …G C C C G G U U G AC C C U G G G C A AG C C C C U U A G G G AG G G C U G C U U C G G C C AG …

A3: …G C C C G G C U G AC C C U G G G C A AG C C C C U U A G G G AG G G C U G C U U C G G C C AG …

Figure 1: mRNA transcript fragments for the normal FGFR3 gene (N) and for the abnormal FGFR3 (A). NOTE: Mutations from the normal sequence are shown in bold underline.

Differences In Primary A.A. Sequence

• Amino Acid Sequence For Normal• ALA|ARG|LEU|THR|LEU|GLY|LYS|PRO|LEU|GLY|GLU|GLY|CYS|PHE|GLY|GLU

• Amino Acid Sequence For Achondroplasia• ALA|ARG|LEU|THR|LEU|GLY|LYS|PRO|LEU|ARG|GLU|GLY|CYS|PHE|GLY|GLU

Differences In Polarity

Argenine (polar)

Small Nucleotide Ribonucleoprotein

• Part of the spliceosome• Removes introns from

mRNA transcript

What Are The Odds…?

Non-Fatal Injuries

• Zipper: 1: 2,600• Toilet: 1: 6,500• Alarm Clock: 1: 350,000• Bed: 1: 400

Fatal Injuries 1

• Snake Bite: 1: 36,000,000• Dog Bite: 1: 20,000,000

Fatal Injuries 2

• Ebola: 1: 14,000,000• Appendicitis: 1: 700

Fatal Injuries 3

• Earth Destroyed By Meteor: 1: 20,000• You Alone Are Killed By Meteor:

1: 150,000,000,000

What Are The Odds That There Is An Exact Duplicate of YOU?

Unlikely…

• 3.2 billion nucleotides in human genome• 97% of this is intron (non-coding), dropping

the number of coding base pairs to 210,000• Two parents = 2^210,000• 1 chance in 10^63,000

• However, only ~108 billion humans have EVER been born.

Probability and Genetics

• Probability: The determination of certain outcomes based upon the number and type of possible outcomes

• Genetics: The determination of heritable outcomes due to the passage of DNA

If the central dogma dictates that DNA is copied in its entirety, and mitosis ensures that each daughter cell gets the same information as the previous, why do organisms need to be different?

Genetic Variety

• Genetic variety ensures that populations/species continue to survive despite changes in their ecosystems

• Populations that do not change genetically must have environments that rarely change

Sources of Genetic Variety

• Mutations– Point Mutations (Single Nucleotide Polymorphisms)– Frameshift/Nonsense Mutations– Chromosomal Mutations

• Sexual Reproduction

Sexual v. Asexual Reproduction

Asexual Reproduction

• Def: Reproduction requiring only one parent/genetic source

• i.e. binary fission, parthenogenesis, budding

• PRO: Quick, Fast, Low Requirements

• CON: Low Genetic Variety

Sexual Reproduction

• Def: Reproduction requiring two parents/genetic sources

• i.e. conjugation, fertilization

• PRO: Genetic Variety• CON: Need water,

partners and GAMETES

GAMETES• Def: Specialized

reproductive cells (i.e. sperm, ovum)

• Gametes contain half the genetic content of other cells in the organism (yet still contain all of the genes)

• To produce another generation, gametes must be fused together to produce a ZYGOTE

Diploid v. Haploid

• Somatic (body) cells are DIPLOID (two sets of chromosomes)

• In each diploid cell, there are pairs of homologous chromosomes containing the same number and type of genes but NOT necessarily coding for identical proteins

• GAMETES are HAPLOID (only one set of chromosomes)

How does a cell go from diploid to haploid and yet retain all of the genes necessary for the organism?

Meiosis

• To develop gametes, a cell must undergo MEIOTIC DIVISION (i.e. MEIOSIS)