Chromosome• 46 inside every cell• Chromosomes are inthe cell in pairs. Dad’s Chromosome Mom’s Chromosome• One came from mom and one came from dad.
DNA - deoxyribonucleic (say: dee-ox-see-ri-bo-nyoo-clay-ik) acid• Long strands of genetic code• Makes up chromosomes in plants and animals DNA
Genes• Tiny pieces of DNA that are instructions for specific traits
Traits• Things that you inherit from your parents• Examples: Hair color, eye color and having freckles or not• Through sexual reproduction you inherited a set of traits
Traits• Pairs of letters are used to define genes in your body• CAPTIAL LETTERS are used to represent DOMINANT genes• lower case letters are used to represent recessive genes• Dominant trait: If you receive even one of these in the pair, you will get a specific trait.• Recessive trait: You have to have two of these in the pair to get a specific trait
Genotypes• The letter associated with the gene ▫ Example: W (dominant widow’s peak) w (recessive no widow’s peak)
Phenotypes• This is the "outward, physical manifestation“• The actual physical trait ▫ Example: You have a widow’s peak.
Allele• Allele: The single letter such as the a or the A.
Heterozygous – having two differentalleles • AA • bb
Homozygous – having the same alleles • Aa • Bb
Purebred or Hybrid?• Purebred: AA or aa• Hybrid: Aa
Practice:B – brown hair b – red hairMy genes: Bb What color hair will I have? Is Bb the phenotype or the genotype? Are my genes heterozygous or homozygous?
Practice:A – attached earlobe a – unattached earlobeMy genes: aa What will my earlobes do? Is attached earlobe the phenotype or the genotype? Is my genotype homozygous or heterozygous?
Practice:D – dimples d – no dimplesMy genes: DD Do I have dimples or not? What is the genotype? Is my genotype heterozygous or homozygous?
QuizF – freckles f – no frecklesMy genes: FF Do I have freckles or not? What is the phenotype? What is the genotype? Is my genotype heterozygous or homozygous? Which parent carried the dominant gene?
Mom Dad hashas brown eyesblue (BB or Bb)eyes Therefore, Dad must(bb) have the Bb genotype, because he must have given her the “b” allele. Daughter His “b” allele is masked by his “B”/dominant has allele.
What is a PUNNETT SQUARE?• A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine• A way to show phenotype & genotype• A chart that showsall the possiblecombinations of allelesthat can result whengenes are crossed
Using a PUNNETT SQUARE To set up a Punnett square, draw a large square, and then divide it into 4 equal sections (also squares). It should look something like this:
Using a PUNNETT SQUARE• Now you need two parents to mate, ones with a known genotype• For example, Brown hair (genotype BB) and blonde hair (genotype Bb). BB x Bb• In this scenario, the Mom has brown hair. The dad blonde hair.
Using a PUNNETT SQUARE Place one of the parents on top, and one on the left. You should get a something similar to this: B b B B
Using a PUNNETT SQUARE• The two-letter combinations are the possible genotypes of offspring• They are: BB, Bb, BB, and Bb genotypes• From this it is possible to determine the probability (chance) that a baby will have a brown phenotype (2/4 or 50%) or a blonde phenotype (2/4 or 50%)
Does it work with animals and plants?• Yes, all of this works the same way in determining the outcome of combining animals and plants.•How can we relate this to selective breeding?•How can we relate this to genetic engineering?