Ch. 13 notes

Ch. 13 notes - Ch. 13 16:45 Genetics the scientific study...

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Ch. 13 16:45 Genetics – the scientific study of heredity and hereditary variation Heredity – inheritance, transmission of traits from one generation to the next Inheritance of genes – coded information in the form of hereditary units Gametes – reproductive cells, vehicles that transmit genes from one generation to the next Somatic cells – all cells of the body except the gametes and their precursors, contain 46 chromosomes Chromosome – a single long DNA coiled in association with various proteins Locus – a gene’s specific location along the length of a chromosome Reproduction Asexual reproduction – a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes Clone – a group of genetically identical individuals Sexual reproduction – 2 parents give rise to offspring that have unique combinations of genes inherited from the 2 parents Offspring vary genetically from parents and siblings Fertilization and meiosis alternate in sexual life cycles Life cycle – generation-to-generation sequence of stages in the reproductive history of an organism, from conception to production of its own offspring Sets of chromosomes Karyotype – ordered display of chromosomes arranged in pairs, starting with the longest chromosomes Homologous chromosomes (“homologs”) - the chromosomes in each pair have the same length, centromere position, and staining pattern, carry genes controlling the same inherited characters Exception: X and Y chromosomes (sex chromosomes) Females: XX Males: XY
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Only small parts of the X and Y are homologous. They determine an individual’s gender The other chromosomes are called autosomes We inherit one chromosome of each pair from each parent The number of chromosomes in a single set = n Any cell with 2 chromosome sets = diploid cell = 2 n For humans, the diploid number is 46 Know the differences between. .. Homologous chromosomes Sister chromatids Nonsister chromatids Chromosome sets Gametes contain only a single set of chromosomes = haploid cells, has a haploid number n For humans, the haploid number is 23 (22 autosomes + 1 sex chromosome) Fruit fly ( Drosophila melanogaster ) – diploid number (2 n ) = 8, haploid number ( n ) = 4 Dogs – diploid number (2 n ) = 78, haploid number ( n ) = 39 Behavior of chromosome sets in the human life cycle Begins when a haploid sperm from the father fuses with a haploid egg from the mother unison of gametes culminating in fusion of their nuclei = fertilization Resulting fertilized egg = zygote = diploid because it contains 2 haploid sets of chromosomes bearing genes representing the maternal and paternal family lines
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This note was uploaded on 03/14/2012 for the course BISC 220 taught by Professor Mcclure during the Spring '09 term at USC.

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Ch. 13 notes - Ch. 13 16:45 Genetics the scientific study...

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