1.2 Genes: Answers and Questions Nitrogenous Base  Codon  Gene  DNA  Chromosome Your future is in your “genes”

1.2 Genes: Answers and Questions (Page 16) Chromosome – a thread-like structure made mostly of DNA, found in the nucleus of a cell DNA (deoxyribonucleic acid) – material found in the cell nucleus that contains genetic information Gene – a segment of DNA that controls protein production Genome Management Information System, Oak Ridge National Laboratory http://genomics.energy.gov Copyright © 2010 McGraw-Hill Ryerson Ltd.

Chromosomes & DNA The nucleus of almost every cell contains chromosomes Chromosomes act like a master set of instructions that determine: what each cell’s job is how it will function how long it will live before being replaced

Genes Direct Protein Production (Page 17) Genome Management Information System, Oak Ridge National Laboratory http://genomics.energy.gov Copyright © 2010 McGraw-Hill Ryerson Ltd.

Chromosomes Chromosomes come in pairs every plant or animal species that reproduce sexually get 1 chromosome from their mother, 1 from their father this means you are 50% your mom, 50% your dad Depending on the species, there could be just a few pairs of chromosomes or many humans have 23 pairs (46 chromosomes) 22 pairs, 1 pair of sex chromosomes everyone’s chromosomes are a little different, which is why we are all different (except identical twins) Chromosomes are composed of coiled strands of genetic information called DNA

Genes Direct Protein Production (Page 17) http://genomics.energy.gov Copyright © 2010 McGraw-Hill Ryerson Ltd.

How many chromosomes? Take a look at the difference in # of chromosome pairs: human  23 pairs (46 chromosomes) butterfly  190 pairs (380 chromosomes) elephant  28 pairs (56 chromosomes) ant  1 pair + (2+ chromosomes) tomato plant  12 pairs (24 chromosomes) shark  41 pairs (82 chromosomes) mosquito  3 pairs (6 chromosomes)

DNA Screening: Testing for Disorders (Pages 19-20) DNA Screening is the process of testing individuals to determine whether they have the gene or genes associated with a certain genetic disorders PKU (phenylketonuria) – mutation in PAH gene Down Syndrome – trisomy 21 Huntington Disease - mutation in HTT gene Cystic Fibrosis – mutation in the CFTR gene Edwards Syndrome – trisomy 18 Copyright © 2010 McGraw-Hill Ryerson Ltd.

Chromosomes of a Human Male Karyotype

Down Syndrome – Trisomy 21

DNA (deoxyribonucleic acid) The genetic material that acts like a master set of instructions for the organism Coiled up strands of genetic information that make up a chromosome Is divided into many genes that control protein production gene = part of a DNA strand

The DNA Code (Pages 17-18) In 1953 scientists James Watson and Francis Crick created this model of DNA (the twisted ladder design is sometimes called a “double helix”). Copyright © 2010 McGraw-Hill Ryerson Ltd.

DNA Made of nitrogen bases, ribose sugars, and phosphate backbones these 3 parts all together are called a nucleotide There are 4 nitrogen bases: adenine thymine cytosine guanine

2 nitrogen bases always pair up: adenine + thymine cytosine + guanine it’s in the gene sequence that we get differences among individuals hair colour, how tall you are, what allergies you have, how quickly your fingernails grow, etc.

Codons: 3-letter words the genetic code is like a book that only has words that are 3 letters long the letters are nitrogen bases (nucleotides) codons are 3-letter words that code for a certain protein to be made ex: CAT, GAG, TAG, … the sequence of codons decides which protein is produced if there’s a mistake in the sequencing of a codon, we get what we know as a mutation ex: CAT, GCG, TAG, …

Comparing Genetic Information to a Book Book component Biological equivalent Letters Words Sentences Paragraph Chapters Book Nucleotides (nitrogen bases) Codons Genes DNA Chromosomes Organism (human, butterfly, ant)

Altering Genes / Transgenic Organisms (Pages 22-23) Transgenic Organism – an organism whose genetic information has been altered with the insertion of genes from another species. These organisms are considered to be genetically modified organisms (GMOs). Possible Uses For GMOs Production of non-allergenic human proteins Development of pest resistant crops Increased growth of crops and livestock Concerns Spread of disease from GMOs Negative effects on ecosystems Allergic reactions from eating GMOs Copyright © 2010 McGraw-Hill Ryerson Ltd.

Cloning (Pages 24-25) Cloning – the process of creating identical genetic copies of an organism Pros and Cons of Cloning Pro: Copies are made of “superior” animals. (increased milk & meat production) Con: Clones may be less disease resistant Copyright © 2010 McGraw-Hill Ryerson Ltd.

Mutations ( Pages 26-27 ) Mutation – a change in the DNA of an organism; usual order of base pairs is altered which changes genes and effects the proteins produced. Not all mutations are harmful as they can occur in a non-genetic segments of DNA. Mutagen – a substance or factor that can cause a mutation in DNA; DNA is physically damaged Examples: radiation (X-Rays, UV radiation), mercury, cigarette tar UV mutated skin cells sickle-shaped blood cells albino American alligator Copyright © 2010 McGraw-Hill Ryerson Ltd.

The Story of Dolly the Cloned Sheep Retro Report | The New York Times https://www.youtube.com/watch?v=tELZEPcgKkE Video 13 min 39 s

Homework  Page 18 # 1-3 Page 22 # 5-7 Page 28 # 1-4