BIOL 1107: Test 4
44 Cards in this Set
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heredity
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transmission of traits from one generation to the next
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Genes
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*coded information that specifies specific traits
*specific DNA sequences tell cells to make enzymes and proteins that lead to different traits
*located along chromosomes and can be tagged with dye
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Gametes
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reproductive cells (egg and sperm) that transmit genes to the next generation
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somatic cells
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*other body cells besides gametes
*each species has a certain number of chromosomes in somatic cells; humans have 46 (23 from each parent)
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diploid
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cells with 2 copies of each chromosome (2n)
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haploid
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cells with only one copy of each chromosome (n)
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locus
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the location of a specific gene on a chromosome
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Asexual reproduction
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one parent produces offspring that are exact genetic copies of the parent
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sexual reproduction
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*two parents produce offspring that have a unique combination of both parents' genes
*offspring are different from the parents and each other
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karyotype
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ordered display of all the chromosomes
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Homologs or Homologous chromosomes
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genes that are the same length, etc. and carry genes controlling the same traits
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sex chromosomes
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*X and Y chromosomes
*females have XX, males have XY
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Autosomes
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chromosomes other that sex chromosomes
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fertilization
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*when sperm and egg join and their nuclei fuze
*2 haploid cells -> diploid
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zygote
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Fertilized egg, diploid cell
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Meiosis
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*Special cell division that produces haploid sperm and eggs
*only diploid cells undergo meiosis
*involves duplication of chromosomes and two cell divisions: meiosis I and II
*produces 4 haploid daughter cells
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Meiosis I
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*homologous chromosomes separate
*crossing over
*ends with 2 haploid cells, each chromosome is still 2 sister chromatids
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Prophase I
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*chromosomes condense and homologs become physically connected
*crossing over happens
*spindles form and nucleus is disassembled
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Crossing over
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*the exchanging of DNA segments between non sister chromatids
*makes recombinant chromosomes that carry genes from both parents
*1-3 crossovers happen per chromosome pair in humans
*recombinant chromatids can be oriented different ways in metaphase II and assort independently again
*t…
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Metaphase I
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homologous chromosomes line up along the center
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Anaphase I
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homologous chromosomes separate and move to poles
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Telophase I and cytokinesis
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*2 haploid cells form
*each chromosome is still 2 sister chromatids
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Meiosis II
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*sister chromatids separate
*4 genetically distinct haploid daughter cells are formed
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Prophase II
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spindle forms
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Metaphase II
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*chromosomes line up in the center
*chromosomes are not identical because of crossing over in meiosis I
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Anaphase II
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Sister chromatids move to poles
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Telophase II and cytokinesis
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*nuclei reform
*chromosomes de-condense
*4 genetically distinct haploid daughter cells are formed
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Alleles
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different versions of a gene
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Independent Assortment of chromosomes
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*homologous chromosomes are oriented randomly in metaphase I
*the maternal chromosome and parental chromosome could be pulled to either pole of the cell
*number of possibilities is 2^n
*component of genetic variation
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Random fertilization
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*any combination of genes in a sperm can fertilize an egg with any possible combination of genes
*component of genetic variation
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Fitness
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*producing offspring
*individuals with combinations of genes best suited to their environment are more likely to survive and reproduce and thus pass those genes on: survival of the fittest
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traits
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*variants on a characteristic
*studied by Mendel
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True breeding plants
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*with self pollination, it produces the same variety as the parent plant over and over
*P is used to refer to the true breeding parents, and F1 is used to me the first generation of offspring, F2 for the next, and so on
*This is the reason why Mendel's studies had such success
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Dominant and recessive traits
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*Dominant traits appear to cover up recessive ones when one dominant and one recessive allele are inherited and when two dominant alleles are inherited
*recessive traits appear when two recessive alleles are inherited
*dominant traits are dominant because they code for enzymes or prote…
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Law of Segregation
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*the two alleles for a characteristic segregate (separate) during formation of gametes and end up in different gametes
*an egg or sperm only gets 1 of the 2 alleles for a trait that end up in the diploid cell
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heterozygous
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having two different alleles for a trait
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homozygous
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having 2 of the same allele for a trait
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phenotype
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an organism's appearance or observable trait
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genotype
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and organism's genetic makeup
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test cross
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breeding an organism of an unknown genotype with a homozygous recessive organism to determine its genotype
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monohybrid
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heterozygous for the particular characteristic being studied in a cross
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monohybrid cross
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*breeding 2 organisms heterozygous for a trait
*leads to a 3:1 dominant to recessive phenotypic ratio
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Dihybrid
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heterozygous for 2 characteristics being studied in a cross
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dihybrid cross
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*breeding 2 organisms heterozygous for the 2 traits being studied
*leads to a 9:3:3:1 phenotypic ratio (dominant & dominant; dominant & recessive; recessive & dominant; recessive & recessive)
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BIOL 1107: Test 4