General Biology BIO 1050 - 02
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This 10 page Class Notes was uploaded by Kara Fields on Monday April 4, 2016. The Class Notes belongs to BIO 1050 - 02 at East Carolina University taught by Dr. Whelan in Spring 2016. Since its upload, it has received 20 views. For similar materials see General Biology in Biology at East Carolina University.
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Date Created: 04/04/16
Biol 1050 Spring 2016 Dr. Whelan Meiosis Sexual Reproduction and Basic Genetics I. Sexual reproduction A. Background a. What characteristic do offspring of asexual reproduction have? Identical to parent. b. What characteristic do offspring of sexual reproduction have? A unique combination of traits and unique genes. c. Describe the number of chromosomes human cells have & how they are arranged in pairs. In humans, all cells (except sperm and egg cells) have 46 chromosomes. = 23 pairs. d. Describe homologous chromosomes. 2 chromosomes of a matching pair. e. These 23 pairs of chromosomes include 22 pairs of autosomes and 1 pair of sex chromosomes. i) What are autosomes? Any chromosome that is not a sex chromosome. ii) What are sex chromosomes? A chromosome involved with determining the sex of an organism, typically one of two kinds. X or Y =X and X or X and Y Biol 1050 Spring 2016 Dr. Whelan iii) What sex chromosomes do human females have? Are they homologous chromosomes? X and Y No, they are not. iv) What sex chromosomes do human males have? Are they homologous chromosomes? X and X No, they are not. f. If a cell is diploid, what does that mean? A cell has a set of homologous chromosomes. i) What is the abbreviation for diploid? 2n ii) What human cells are diploid? All except gametes (=sperm and egg cells) iii) How many chromosomes do diploid human cells contain? 46 total chromosomes. g. If a cell is haploid, what does that mean? A cell has only one of each chromosome type. i) What is the abbreviation for haploid? n Biol 1050 Spring 2016 Dr. Whelan ii) What human cells are haploid? Gametes (=sperm and egg cells) iii) How many chromosomes do haploid human cells contain? 23 total. h. What are gametes? Sperm or egg cells. i. What are the two types of cell division in eukaryotes? 1) Mitosis 2) Meiosis i) What types of cells does meiosis create? Cell division used to make sperm and eggs only. ii) What happens if there are errors during meiosis? Mistakes can lead to disorders like Down Syndrome. iii) Describe meiosis. The process that produces haploid gametes in diploid organisms. iv) How many cell divisions occur during meiosis and how many cells are produced? 2 divisions of meiosis. 4 haploid cells. Of which 2 contain a single copy of one of the original chromosomes and the other 2 contain a single copy of the other chromosome. j. What is a life cycle? Biol 1050 Spring 2016 Dr. Whelan The series of changes in the life of organisms, including reproduction. i) What is a zygote? A fertilized egg. ii) Describe the life cycle of a human. Adult females and adult male= diploid cell Meiosis= egg and sperm= haploid cell Fertilization= fertilized egg= diploid cell Mitosis= offspring B. Origins of genetic variation a. What are 2 reasons why offspring from sexual reproduction are genetically different from their parents & each other? 1) Random Fertilization 2) Crossing Over b. Describe what we mean by random fertilization. Multiple eggs and lots of sperm produced Only one egg and one sperm unite Random which egg and which sperm it is c. What is crossing over? Exchange of genetic material between homologous chromosomes. i) What is the result of crossing over? Each chromosome becomes a mixture of information from mom and dad. Biol 1050 Spring 2016 Dr. Whelan ii) Why is crossing over important? Produces gene combinations different from those carried by the parents’ chromosomes. C. Twins a. How are fraternal (dizygotic) twins formed? Egg and Sperm Zygote Embryo Baby 50% Identical. Egg and Sperm Zygote Embryo Baby Just like having any other siblings. b. How are identical (monozygotic) twins formed? Egg and Sperm Zygote Embryo Embryo splits Two Embryos Two Babies 100% genetically identical II. Basic Genetics A. Chromosomes and alleles a. Do both copies of our genes code for the same version of a trait? No. Different version of a trait. b. What is an allele? Each different version of a trait. c. Give an example of a gene and an allele. Gender Allele Hair Color Brown or Blonde Eye Color Blue or Green d. Alleles can be either ___Dominant___ or __Recessive__. e. What does it mean for an allele to be dominant? Version of trait fully shows. f. What does it mean for an allele to be recessive? Biol 1050 Spring 2016 Dr. Whelan Version of trait can be hidden. g. What is homozygous dominant? 2 Dominant Alleles. h. What is heterozygous? 1 Dominant, 1 Recessive Allele. i. What is homozygous recessive? 2 Recessive Alleles. B. Crosses a. What is a monohybrid cross? A cross between parents that differ in only one characteristic. (e.g. color) b. What is a genotype? An organisms’ genetic makeup. (e.g. Aa) c. What is a phenotype? The trait an organism shows (e.g. red) Physical traits d. Explain the P generation, 1 generation, and 2 generation Alleles Alleles P RR rr F1 All Rr Biol 1050 Spring 2016 Dr. Whelan F2 Rr Rr C. Describe how to make a Punnett Square (i.e., how many squares, what goes in each column of the square, etc.) to solve monohybrid crosses. Rr X Rr 1 Allelle from Mom 1 Allele from Dad Dominant is CAPITAL letter Recessive is lower case letter a. Draw a Punnett Square for a cross between two heterozygous individuals. R r R RR Rr r Rr rr b. If purple flowers are dominant to white flowers in the example above, what phenotypes are present in the 2 offspring and in what proportions? Phenotype= ¾ purple, ¼ white c. What are the genotypes and their proportions from this example cross? Genotype= ¼ RR, ½ Rr, ¼ rr III. Human Genetics A. Background a. Who discovered the basic patterns of inheritance? Mendel Biol 1050 Spring 2016 Dr. Whelan b. To what kind of human traits do Mendel’s principles apply? Dominant Recessive Cleft Chin Noncleft Chin Unattached Earlobes Attached Earlobes Widow’s Peak Straight Hairline B. How are many human disorders controlled? By a single gene, an autosome. C. What does it mean for a condition to be recessive? To be dominant? Two copies of an abnormal gene must be present in order for the disease or trait to develop. An abnormal gene from only one parent. If you inherit it, you can get the disease. a. Are most disorders recessive or dominant? Recessive b. Who are carriers? What possible genotype(s) can a carrier have? Have 1 recessive allele for disease, but no symptoms. c. List examples of recessive disorders. Sickle Cell Anemia Cystic Fibrosis PKU d. Describe cystic fibrosis Effects the exocrine glands. Often resulting in respiratory infection Biol 1050 Spring 2016 Dr. Whelan Hereditary disorder. e. What happens when 2 carriers mate? For both being heterozygous. 25% chance they will get it. 50% chance they will be carriers. 25% chance they won’t have it at all or be a carrier. D. Dominant disorders a. Are dominant alleles necessarily better than the corresponding recessive allele? They are not better. They are more likely to occur and be passed down. b. Are dominant alleles necessarily more common than the corresponding recessive allele? Isn’t always the case. Whether or not a trait is common has to do with how many copies of that gene version are in the population. c. Why are lethal dominant disorders rare? Lethal Dominant disorders are rare because… Those affiliated usually die before reproducing (including heterozygous). d. How can a lethal dominant disorder get passed on from generation to generation? Can remain if it doesn’t kill until after person has kids. e. List examples of dominant disorders. Neurofibromatosis type 1 Huntington’s Disease Biol 1050 Spring 2016 Dr. Whelan f. Describe Huntington’s disease A hereditary disease marked by degeneration of the brain cells and causing chorea and progressive dementia. Ex… 1 (mom) with disorder. 50% chance will. 50% chance will not 1 (dad) with homozygous dominant allele. Every single one of his kids will get the disease.
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