Chapter 11 Bio 1010 03 04 2014 Cancer Genetics As cells accumulate mutations over time Exposure to carcinogens and repeated rounds of cell division increase the chances of mutation accumulation Mutagens are chemical or physical agents that can damage DNA by changing its nucleotide sequence Carcinogens are mutagens that cause cancer by damaging DNA A mutation is a change in the nucleotide sequence of DNA which creates alternative alleles of a gene Cystic fibrosis Mutations in the cystic fibrosis transmembrane regulator gene Chromosome 7 Cystic fibrosis results from a recessive allele Produces abnormally thick mucus that builds up in the lungs In people with CF the CFTR protein is distorted Genes are units of inheritance Genes are physically transmitted from parents to children The alleles of your genes represent mother father and other family members Not every child of a couple receives the exact same parental genes Humans are diploid organisms Two copies of every chromosome One from the biological mother and one from biological father These paired chromosomes are called homologous chromosomes Two pairs have the same general function Nucleotide sequence of each copy can differ o A person can carry two different alleles of the same gene These two alleles make up your phenotype and genotype Phenotype includes the visible or measurable features of an individual Genotype is the particular genetic makeup of an individual Humans reproduce sexually Parents pass their genes to their offspring Gametes are specialized reproductive cells that carry one copy of each chromosome These are haploid cells 23 chromosomes Haploid the cells that form gametes go through cell division called meiosis This process halves the chromosome number from 46 to 23 Meiosis results in genetically unique haploid gametes Haploid sperm haploid egg diploid zygote Zygote carries two copies of every gene o Has 23 chromosomes Meiosis other A form of cell division that ends in four daughter cells that have half the information of the mother cell and different from each Genetic diversity of an offspring No two gametes produced by the same parent are identical due to two major events during meiosis recombination and independent assortment Recombination occurs when maternal and paternal chromosomes pair and physically exchange DNA segments Independent assortment maternal and paternal pairs of chromosomes separate according to how they have randomly aligned Trait inheritance Homozygous having two identical alleles o AA aa two recessive or two dominant Heterozygous having two different alleles o Aa o This is also considered being a carrier carry both alleles Dominant Allele an allele that can mask the presence of a Recessive allele an allele that reveals itself only if the organism recessive allele has two copies of that allele Autosomes 22 paired chromosomes present in both males and females XX female XY males Sex chromosome paired chromosomes that differ between males Y chromosome triggers males developmental pathway during and females fetal development X linked trait A phenotype determined by an allele on an x chromosome Goals of pedigree analysis To determine the mode of inheritance dominant or recessive 03 04 2014 03 04 2014