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Transcript
UNIT 2: GENETICS MEIOSIS WARM-UP Recall that chromosomes are composed of DNA and contain the genetic blueprint for an organism. Each species has its own unique set of chromosome, and all individuals in a particular species typically have the same number of chromosomes. Humans have 46 chromosomes. The domestic dog has 78 chromosomes, the domestic cat has 38 chromosomes, and the mouse that it chases has 40 chromosomes! Within each individual in a species, every somatic cell (not a sex cell) contains the same number of chromosomes as every other. Humans (and most other animals) are diploid organisms meaning that each cell contains two complete chromosome sets. 1. Where did the two chromosome sets originate? How do parents' genes get passed to their offspring? 2. The genetic make up of the sex cells of an individual are based on that person’s DNA. Are all the sperm cells identical in a male? Are all the egg cells identical in a female? How do you know? (hint: think about the genetics of your sister/brother) 3. Normal humans carry 46 chromosomes in each cell (2 copies of 23 chromosomes). Why do we have two copies of each of the genes in our genome? 4. Can we pick out which genes we want our children to inherit? 5. Human gametes (sex cells) are haploid cells, meaning that they have only one complete set of chromosomes. If human somatic cells have 46 chromosomes, how many chromosomes do human gametes have? 6. When fertilization occurs, the haploid sperm cell and haploid egg cell join, producing a fertilized zygote. This "restores" the diploid chromosome number. How many chromosomes do fertilized eggs contain? Are fertilized eggs haploid cells or diploid cells? UNIT 2: GENETICS Define the following terms: germ/sex cells somatic cells diploid haploid meiosis gamete genome chromosome homologous chromosomes gene allele phenotype genotype sister chromatids centromere interphase cytokinesis UNIT 2: GENETICS germ/sex cells reproductive cells, contain a haploid number of chromosomes. somatic cells not germ cells. These cells contain a diploid chromosome number diploid twice the number of chromosomes in a gamete. Every cell in the body, except for sex cells, contains a diploid chromosome number. haploid meiosis number of chromosomes in a gamete – half of the number of chromosomes in a somatic cell two-stage cell division in which the chromosome number of the parental cell is reduced by half. Gametes form through meiosis. gamete sex cells that have a haploid chromosome number genome the complete set of instructions contained within the DNA of an organism chromosome the packaging of DNA and proteins homologous chromosomes gene paired chromosomes similar in shape, size, gene arrangement and gene information part of DNA that codes for a protein UNIT 2: GENETICS allele sister chromatids alternate forms of a gene, ex. blue eyes and brown eyes. Alleles are located in the same position on homologous chromosomes. the observable trait of an organism, ex. brown eyes the alleles (code) an organism contains, ex. allele for brown eyes and blue eyes a chromosome and its copy, attached to one another at the centromere centromere structure that holds chromatids together interphase the time between nuclear divisions, when a cell grows and copies its chromosomes to make sister chromatids division of cytoplasm that leads to formation of two new cells phenotype genotype cytokinesis