Genes+and+Alleles

Genes and Alleles (Cornell style notes) 1 Genes are codes in the DNA that controls traits. 2 Each parent gives an offspring a gene for a trait. 3 The two genes received for a trait can be the same or different. 4 The different forms of a gene are called alleles. 5 Some alleles are dominant and others are recessive. 6 Two recessive alleles must be present to produce a recessive trait. 7 Purebreds can have two dominant or two recessive alleles. 8 Hybrids have one dominant and one recessive allele. 9 Dominant alleles are represented with capital letters. 10 Recessive traits are represented with lower case letters.

Old - 1. DNA is a long, thin molecule that looks like a twisted ladder with rungs made of base pairs: GC and AT. 2. Chromosomes are pieces of DNA in the nuclei of each cell. Humans have 23 pair. 3. Genes are a sequence of bases in a chromosome that code for a trait. 4. Chromosome pairs – one comes from each parent to make up the pair. 5. Sexual reproduction results in offspring that are genetically different from their parents. 6. Asexual reproduction results in offspring that are genetically the same as their parents. 7. Alleles are different forms of a gene. 8. Organisms get one allele from each of their parents. 9. An organism's alleles can be the same or different. 10. In purebreds, alleles are the same. 11. In hybrids, alleles are different and the dominant allele is responsible for the trait. 12. Dominant - Allele represented by the upper case letter. Only one dominant allele is needed to produce the trait. 13. Recessive - Allele represented by a lower case letter. Two recessive alleles are needed to produce the trait. 14. Phenotype - what it looks like - physical appearance - visible traits 15. Genotype - The alleles it has - allele combinations (letters) 16. Homozygous - has the same alleles. (TT or tt) 17. Heterozygous - has different alleles. (Tt) 19. Dominant Alleles – capital letters Recessive Alleles – lower case letters

http://news.yahoo.com/gene-variant-tied-time-sitting-body-mass-index-190419602.html

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https://www.yahoo.com/news/gene-therapy-lets-french-teen-dodge-sickle-cell-220213538.html