2(DNA- DeoxyriboNucleic Acid) NucleusOur cells are controlled by the nucleus. The nucleus also contains our genetic information(DNA- DeoxyriboNucleic Acid)on structures calledChromosomes.
3Chromosomes Humans have 46 chromosomes in each body cells or 23 pairs. Pea Plants have 14 chromosomes in each cell or 7pairs.Made of thousands of genes (over 60,000 in humans).Each parent contributes half of each chromosome pair to their offspring.Usually there is one pair of sex chromosomes
4GenesThe genes on chromosomes have control for different traits. For example a gene may control for eye color. All genes come in pairs.Half of the pair coming from mother, the other half coming from fatherHumans: 23 genes from mother (XX)23 genes from father (XY)Pea Plants 7 genes from mother (XX)7 genes from father (XY)
5AllelesThere are different forms of genes called alleles. For example: eye color (gene) brown eyes, blue eyes, and green eyes (allele)
6Dominant Allele vs Recessive Allele Individual C is the only one who will have blue eyes (recessive allele)Because the allele for brown eyes is present, individual B and individual A will have brown eyes
7Dominant Allele vs Recessive Allele Dominant allele – a trait that always shows up when the allele is presentSymbol – Capital letter (T)Recessive allele – a trait that is covered up or masked when a dominant allele is presentSymbol – lower case letter (t)For example brown eyes (B) are dominant over blue (b), and appear more often.
8Allele: Eye Color B represents the dominant trait brown b represents the recessive trait of blue.the child could have B from one parent and B from the other = child with brown eyesGENOTYPE: BB PHENOTYPE: Brown Eyesthe child could have B from one parent and b from the other = child with brown eyesGENOTYPE: Bb PHENOTYPE: Brown Eyesthe child could have b from one parent and b from the other = child with blue eyesGENOTYPE: bb PHENOTYPE: Blue EyesAny time the dominant gene appears, the offspring will have the dominant trait.
11Let’s Review: Beach Ball Activity What is the phenotype for Bb when b= blue eye color and B= brown color?What is a phenotype and a genotype?When does a phenotype for a recessive trait show up in an organism?How many pairs of chromosomes do humans have?T = tall and t= short, what is the phenotype for Tt?T = tall and t= short, what is the phenotype for tt?T = tall and t= short, what is the phenotype for TT?Sex chromosomes for males is?