BIOL FINAL – 8, 9 – Flashcards
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A special kind of cell division called meiosis occurs in the ovaries and testes, producing _____
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haploid gametes- eggs and sperm- that carry only one set of 23 chromosomes each
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Fertilization of an egg by a sperm combines two sets of chromosomes, producing a
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diploid zygote with 46 chromosomes
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Meiosis produces _______ and fertilization produces ________.
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haploid gametes, diploid organisms
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Meiosis is essential to sex, because it enables each parent to contribute
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one set of chromosomes to each diploid offspring
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What happens during interphase before meiosis?
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chromosomes replicate
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Unlike mitosis, where each chromosome is on its own, in meiosis I homologous chromosomes pair up, and each pair separates, producing
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two haploid cells with their sister chromatids still joined
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Meiosis II is like _____.
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Mitosis Sister chromatids separate and four haploid cells are formed
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Asexual reproduction is the process in which
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a single individual is reproducing
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Gametes are produced by
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meiosis
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Normal human gametes carry
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23 chromosomes
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Once meiosis I is complete, cells are ______.
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haploid
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A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.
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16
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A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.
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False; Mitosis does indeed take place during M phase, but M phase is shorter than interphase; cells spend most of their time in interphase.
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A certain species of animal has six pairs of chromosomes. How many DNA molecules are present in the nuclei of these animals during G2 phase?
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24; DNA replication is completed during S phase, which occurs prior to G2 phase. Since each chromosome (12) is replicated, there are 24 DNA molecules in the nucleus during G2 phase.
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Cell division occurs during this short phase, which generally involves two discrete processes: the contents of the nucleus (mainly the duplicated chromosomes) are evenly distributed to two daughter nuclei, and the cytoplasm divides in two.
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Mitotic Phase
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DNA synthesis (or replication) occurs during this phase. At the beginning of the phase, each chromosome is single. At the end, after DNA replication, each chromosome consists of two sister chromatids.
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S phase
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Typically, this phase accounts for 90% of the cell cycle. It is a time of high metabolic activity. The cell grows by producing proteins and organelles, and chromosomes are replicated.
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Interphase
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Typically, this phase accounts for 90% of the cell cycle. It is a time of high metabolic activity. The cell grows by producing proteins and organelles, and chromosomes are replicated.
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Mitosis
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This third subphase of interphase is a period of metabolic activity and growth. During this phase the cell makes final preparations for division.
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G2 phase
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This is the portion of the cell cycle just after division, but before DNA synthesis. During this time the cell grows by producing proteins and organelles.
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G1 phase
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This is the step in the cell cycle when the cytoplasm divides in two.
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Cytokinesis
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During _____ both the contents of the nucleus and the cytoplasm are divided.
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the mitotic phase
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During _____ the cell grows and replicates both its organelles and its chromosomes.
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interphase
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What occurs during prophase?
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Mitotic spindle forming
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What occurs during metaphase?
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Sister chromatids centered
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What occurs during anaphase?
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Chromosomes separating
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What occurs during telophase and cytokinesis?
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Nuclear envelops forming
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What must happen before a cell can begin mitosis?
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The chromosomes must be duplicated.
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The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
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Prophase
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The chromosomes line up in the center of the cell during which phase of mitosis?
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Metaphase
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The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
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Anaphase
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The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
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Telophase
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At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.
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Cytokinesis
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A _____ is a lump of abnormal cells that, although growing out of control, remains at its original site.
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benign tumor
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A _____ is an abnormally growing mass of cells that is actively spreading throughout the body.
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malignant tumor
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_____ is the spread of cancer cells from their site of origin to other sights in the body
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Metastasis
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An individual with a malignant tumor is said to have _____.
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cancer
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The most common type of cancer is a _______; this type always originates in tissues that line organs.
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carcinoma
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A normal gene that, if mutated, can lead to cancer is called a _________.
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proto-oncogene
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A gene that causes a cell to become cancerous is called a(n) ______.
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oncogene
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A(n) ______________ that encodes proteins that inhibit cell division. Such proteins normally help prevent cells from becoming cancerous.
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tumor-suppressor gene
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A(n) ____________ is a protein that promotes cell division. In excess, such a protein may lead to cancer.
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growth factor
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_____ is a carcinogen that promotes colon cancer.
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Fat
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_____ is a carcinogen that promotes lung cancer.
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Smoking
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______ is a carcinogen that promotes prostate cancer.
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Testosterone
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______ is a carcinogen that promotes uterine cancer.
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Estrogen
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______ is a carcinogen that promotes skin cancers.
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UV light
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_____ are a carcinogen that promotes cancer of lymphatic cells (lymphomas).
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Viruses
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Meiosis I produces _____ cells, each of which is _____.
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two; haploid
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Meiosis II typically produces _____ cells, each of which is _____.
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four; haploid
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During _____ sister chromatids separate.
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anaphase II
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At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.
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telophase I
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Synapsis occurs during _____.
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prophase I
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Homologous chromosomes migrate to opposite poles during _____.
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anaphase I
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During _____ chromosomes align single file along the equator of a haploid cell.
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metaphase II
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At the end of _____ and cytokinesis there are four haploid cells.
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telophase II
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During _____ a spindle forms in a haploid cell.
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prophase II
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Meiosis starts with a single diploid cell and produces
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four haploid cells
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A cell preparing to undergo meiosis duplicates its chromosomes during
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interphase
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During prophase I of meiosis,
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homologous chromosomes stick together in pairs
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The correct order of events during meiosis is
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prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II
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During meiosis, segments of nonsister chromatids can trade places. This recombination of maternal and paternal genetic material is a key feature of meiosis. During what phase of meiosis does recombination occur?
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prophase I
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Mitosis goes on continuously in most parts of the body, whereas meiosis takes place only in
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the gonads
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Meiosis I is the only time that chromosomes line up by
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homologous pairs
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The centromere is the point of attachment between two
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duplicated chromosomes
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Pairing of homologous chromosomes is followed by
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crossing over, the exchange of genetic material between nonsister chromatids of homologous chromosomes.
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Asexual reproduction is a means of creating new individuals solely by
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mitosis, the form of cell division that creates genetically identical daughter cells
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Looking into your microscope, you spot an unusual cell. Instead of the typical rounded cell shape, the cell has a very narrow middle separating two bulging ends. It sort of looks like the number 8! Then you realize that this cell is
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undergoing cytokinesis
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Mutations in the p53 gene can lead to cancer by
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causing the production of a faulty protein that is no longer able to inhibit cell division.
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the conclusion of meiosis I, the daughter cells are _____.
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haploid and the sister chromatids
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Crossing over is a phenomenon that creates genetic diversity during
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meiosis
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Genetic diversity is enhanced by
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crossing over during meiosis, independent orientation of chromosomes at metaphase I and random fertilization
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A ______ is an inherited feature that varies from individual to individual
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character
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A ______ is one particular variation of a character.
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trait
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A genetic cross involving parents that differ in a single character is called a
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monohybrid cross
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Most human genes come in alternate forms called
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alleles.
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If an organism has two non-identical versions of a gene, the one that is expressed in the organism is called the ______ allele.
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dominant
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If an organism has two non-identical versions of a gene, the one that is not expressed in the organism is called the ______ allele.
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recessive
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The physical traits of an organism
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phenotype
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The genetic makeup of an organism
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genotype
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A cross between two individuals with black eyes and green skin which results in an individual with orange eyes and white skin is an example of a _____ cross.
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dihybrid
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A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.
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both parents are heterozygous for both genes
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In a situation in which genes assort independently, what is the ratio of the gametes produced by an AaBB individual?
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1 AB; 1 aB
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(With some exceptions) DNA is a double-stranded molecule and RNA is a
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single-stranded molecule
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In a nucleotide, the nitrogenous base is attached to the sugar's _____ carbon and the phosphate group is attached to the sugar's _____ carbon.
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1'......5'
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Nucleic acids are assembled in the _____ direction.
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5' to 3'
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In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
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thymine.. cytosine
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The central dogma describes how the genes in the nucleus work to produce an organism's phenotype. Another way of putting it is that the central dogma follows the flow of information from _____.
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DNA to protein
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DNA carries out two basic functions in cells: (1) information storage and transfer (genes can be copied and passed to offspring) and (2) the "blueprint" function (genes provide instructions for building proteins). The key process for information storage and transfer to offspring cells is _____.
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DNA replication
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tRNA molecules work to _____.
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translate mRNA to produce a specific amino acid sequence
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A particular gene does NOT constantly churn out the same protein at all times in every cell. This is true for two reasons. First, _____ can allow one gene to produce several different proteins. Second, genes are constantly being turned on and off through the process of _____.
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mRNA reprocessing...gene regulation
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Short segments of newly synthesized DNA are joined into a continuous strand by _____.
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ligase
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After DNA replication is completed, _____.
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each new DNA double helix consists of one old DNA strand and one new DNA strand
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Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?
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it is more efficient than assembling completely new strands
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An old DNA strand is used as a _____ for the assembly of a new DNA strand.
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template
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How do mutations affect an organism?
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they may cause the development of a disease-causing allele, of a more beneficial allele, or may have no noticeable effect
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A female that is planning to become pregnant is concerned about her exposure to environmental mutagens which may have caused DNA mutations. In order for these mutations to become heritable, they must affect the:
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her egg cells
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Which of the following would indicate a base pairing mutation in DNA?
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a G paired with a T
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Replication occurs in the
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nucleus
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Transcription occurs in the
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nucleus
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Translation occurs in the
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ribosomes
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An insect that has the genotype EeGGcc will have the same phenotype as an insect with the genotype _____.
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EEGgcc
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Consider the following sequence and explain what effect the mutation has on the protein that is translated. UCUAUGUUUCACAGAGGGAAACCCUAACCC (wild type) UCUAUGUUUCACUGAGGGAAACCCUAACCC (mutant)
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prematurely stops the translation of the protein
