Bio Chapter 6: Meiosis and Mendel – Flashcards
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What are the two types of specialized cells?
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Somatic and Germ
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What kind of cells are somatic?
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genetically identical body cells in tissues and organs
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What happens to DNA in somatic cells?
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It is not passed on to offspring
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What kind of cells are germ?
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genetically different reproductive cells in reproductive organs
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What do germ cells develop into? How?
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Gametes through meiosis
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What are gametes?
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sex cells: ova/eggs, spermetozoa/sperm
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What happens to DNA in a germ cell?
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it's passed on to offspring
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What differentiates chromosome numbers in organisms?
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Each species has a certain number of chromosomes per cell
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In which type of cell does the number of chromosomes differ?
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gametes
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What does complexity of an organism have to do with the number of chromosomes?
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nothing
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Cells with the same number of chromosomes are genetically identical unless ______________.
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a mutation occurs
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How many chromosomes does a human have?
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46 in 23 pairs
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What does each somatic cell contain?
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22 autosomes and 1 sex chromosome
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What are autosomes?
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Chromosomes #1-22
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Autosomes are homologous. What does this mean?
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they are alike in appearance; one is from the mother, one is from the father
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What do homologous chromosomes (1 from mom, one from dad) contain?
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copies of the same gene-- may differ
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in what order are the chromosomes aligned from 1-22?
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largest to smallest
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What genes do homologous chromosomes carry?
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genes not directly related to the sex of the organism
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What is the 23rd pair of chromosomes called?
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sex chromosomes
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What kind of genes do sex chromosomes contain?
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genes directly related to the sex of the offspring
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Are sex chromosomes homologous?
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no
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What is the type of sex chromosome pair for a female? For a male?
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XX, XY
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What is the Y chromosome like?
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small, has few genes
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What are diploid cells?
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cells that contain 2 copies of each chromosome, 1 from mom, 1 from dad (aka body cells)
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What is the letter symbol for a diploid cell?
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2n
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What is a haploid cell?
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a cell that has 1 copy of each chromosome (aka gamete cell)
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What is the letter symbol for a haploid cell?
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n
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What is sexual reproduction?
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The fusion of 2 gametes
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What does sexual reproduction result in?
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offspring with a genetic mixture
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What is fertilization?
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fusion of the egg and sperm
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What happens to the nucleus in fertilization?
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the 2 nuclei fuse to form one
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What is a requirement for sexual reproduction?
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the finished cell must only have 46 chromosomes, so the 2 parent cells must only have 23
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What occurs in Meiosis I?
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Germ cells (diploid) ------> Gametes (haploid)
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Whats another name for meiosis?
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reduction division
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What are the three purposes of meiosis?
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1) reduce chromosome # 2) bring genetic diversity 3) make gametes
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What are the "reactants" and "products" of meiosis?
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1 diploid cell ------> 4 haploid cells
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What are the 2 rounds of Meiosis?
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Meiosis I and Meiosis II
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How many stages does each round have?
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4
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What is divided in meiosis I?
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homologous chromosomes
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What is divided in meiosis II?
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sister chromatids
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What is the first stage of Meiosis I?
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Prophase I- spindle fibers form, nuclear membrane disintegrates, DNA coils, Synapsis
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What is Synapsis?
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homologous chromosomes pair up; tetrad- four chromatids, genes are side-by-side, crossing over occurs, portions of chromosomes are exchanged, genetic recombination
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What is the second stage of Meiosis I?
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Metaphase I- pairs line up randomly at equator, creates/maintains genetic diversity (2 ^23)
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What is the third stage of Meiosis I?
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Anaphase I- homologous chromosomes move to opposite poles
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What is the fourth stage of Meiosis I?
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Telophase I- cell divides, membrane forms
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What is formed after cytokinesis?
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2 nonidentical cells
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What is the first stage of Meiosis II?
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Prophase II- "
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What is the second stage of Meiosis II?
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Metaphase II- "
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What is the third stage of Meiosis II?
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Anaphase II- sister chromatids pulled apart
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What is the fourth stage of Meiosis II?
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Telophase II- cels divide
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What does Meiosis II skip? Why?
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Interphase- dont want DNA to replicate
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What is formed when cytokinesis occurs after meiosis II?
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4 haploid cells
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When does Gametogenesis occur?
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After Meiosis II
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What is Gametogenesis?
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when germ cells form gametes
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What is sperm-formation called?
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spermatogenesis
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What happens in spermatogenesis?
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meiosis occurs in testes 1 cell forms 4 spermatids, which mature to sperm
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What is egg-formation called?
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oogenesis
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What occurs in oogenesis?
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meiosis occurs in ovaries 3 polar bodies and one egg formed cytoplasm divided unequally
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What is the purpose of polar bodies?
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to dispose of extra chromosomes they eventually disintegrate
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Who was Mendel?
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"Father of Genetics" Austrian Monk, Mathematician, Botanist Pea plants experiment
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Why did mendel use pea plants?
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1- reproduce quickly 2- can self pollinate or cross pollinate 3- they're easy to grow 4- large # of offspring 5- mature quickly 6- 7 distinct monohybrid characteristics
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What is Genetics?
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the study of inheritance patterns and traits/ how organisms get them
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What is a pure bred?
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only one traint exists and each gene is the same
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What is the law of segregation?
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Organisms get 2 copies of 1 gene Organisms donate only 1 copy in gametes Traits are inherited as discrete units during anaphase II
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What are genes?
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pieces of DNA that provide a set of instructions for a cell to make a certain product
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What are alleles?
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any of the alternative forms of a gene that may occur at a specific locus
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How many alleles per gene?
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2; 1 on each homologous chromosome
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What are the 2 classifications for an allele?
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Homozygous and Heterozygous
