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Bio Ch 7-9
Midterm II
| Question | Answer |
|---|---|
| The building block of nucleic acids is a(n) | nucleotide |
| Complementary DNA strands are held together by | hydrogen bonds |
| The enzyme that unwinds and separates the paired DNA strands is | helicase |
| The enzyme that joins Okazaki fragments is | ligase |
| The enzyme that builds a short complementary piece of RNA at the start of each DNA segment to be replicated is | primase |
| The enzyme that adds nucleotides along the 5' to 3' along a DNA strand, is | DNA polymerase |
| Apoptosis is a name for the process of | programmed cell death |
| Before any cell divides into two daughter cells, it must first duplicate its | cytoplasmic contents/organelles, array of enzymes. and entire genome |
| A nucleosome consists of | a stretch of DNA and histones |
| The process by which a sperm cell combines with an egg cell is | fertilization |
| Meiosis is a process used for | production of gametes |
| The two main stages of the eukaryote cell cycle, in which the cell spends most of its time and metabolic energy, are | interphase and mitosis |
| While in the biology lab, you observe, in both plant and animal cells, that some single cells are splitting into two daughter cells, in the process of | cytokinesis |
| The correct sequence for the phases of the cell cycle, starting with a newly divided cell, is | interphase - mitosis - cytokinesis |
| The correct sequence for the phases of mitosis, shown in correct sequence in this diagram, is | prophase - prometaphase - metaphase - anaphase - telophase |
| The phase of mitosis in which the centromeres split and sister chromatids are pulled to opposite poles of the cell is | anaphase |
| The phase of mitosis in which the chromosomes condense and centrosomes move to opposite poles of the cell is | prophase |
| The phase of mitosis in which the nuclear envelope reforms is | telophase |
| The phase of mitosis in which the chromosomes are aligned along the equator of the cell is | metaphase |
| If one strand of a DNA molecule has the base sequence of 5'-ATGTGCC-3' the complementary strand of DNA will read | 3'-TACACGG-5' |
| If a mutation causes the "T" base in the base sequence 5'-AGTCCG-3' to be read as a "G" base, DNA replication of the mutated sequence will read: | 3'-TCCGGC-5' |
| In order for a cell to become cancerous, oncogenes must be ___, or tumor suppressors are ___. | activated; inactivated |
| You are shown petri dishes of cheek cell cultures. 1 set of cells is thin, with individual cells arranged in a single, orderly layer. The other culture shows irregular crowding of cells. The crowding cells are likely cancer cells, showing an absence of | contact inhibition |
| Sexual reproduction is important to the survival of a species in a changing environment because | sexual reproduction produces genetically variable individuals in the population |
| The human chromosomes that do not determine whether an individual is male or female are | autosomes |
| The chromosomal combination for a human male is | XY |
| The chromosomal combination for a human female is | XX |
| The process by which homologous chromosomes exchange genetic material | is crossing over |
| Nondisjunction may cause | Trisomy 21, Turner syndrome. and Klinefelter syndrome |
| How many of the mother's chromosomes are present in the egg before it is fertilized? | 23 |
| The movement of a section of DNA from a chromosome to a non-homologous chromosome is an example of | translocation during meiosis |
| Which of the following statements is correct about epigenetic mechanisms? | They occur early in life, Methylation is an epigenetic mechanism associated with methylation of cytosine that is situated next to a guanine, Mods of histones can turn ON/OFF gene expression depending on the type of mods that occur along the histone tai |
| Which of the following diseases are due to a translocation of a piece of a chromosome from one location to another? | Acute Myelogenous leukemia |
| A three-base sequence (loop) in tRNA that is complementary to a sequence of three bases in mRNA is a(n) | Anticodon |
| The step of translation in which amino acids are added one at a time to the growing polypeptide is | elongation |
| Which one of the following plays a role in transcription? | RNA polymerase |
| Poly A tail and mRNA cap are added during | mRNA processing |
| The codon is a sequence of nucleotide that belongs to | mRNA |
| Which one of the following is not a stop codon? | AUG |
| Which of the following statements is correct? | Translation is efficient since many ribosomes attach to mRNA leading to the formation of many polypeptides |
| Which of the following statements is/are correct? | Frameshift mutations affect multiple codons, Insertion of one nucleotide changes every codon after the insertion, and Substitution of one nucleotide by another can lead to the formation of a different amino acid |
| Sickle cell anemia is a disorder that results from a | Substitution |
| What type of mutation has occurred in the following? Normal allele 5'–GGAAUGAAACAGGAACCC–3' Mutant allele 5'–GGAAUGAAAUCAGGAACCC–3' | insertion of one base |
| The 5' and 3' designations used in reference to DNA and RNA sequences are assigned to the | carbon atoms of deoxyribose and ribose |
| The DNA sequence 5'–ATCGATCG–3' will pair with which of the following RNA strands? | 5'–AUCGAUCG–3 |
| If the DNA in a cell consists of 20% A, it will be ___ G. | 30% |
| DNA stores... | the information that the cell needs to produce proteins |
| Hereditary information | Is encoded in the chemical language of DNA and reproduced in all the cells of your body |
| It is the DNA program that | directs the development of many different types of traits (biochemical, anatomical, physiological and behavioral) |
| DNA is a | polymer of nucleotides |
| DNA consists of | a nitrogenous base, a sugar, and a phosphate group |
| In all organisms, the number of adenines was approximately _______ to the number of thymines | equal |
| The number of guanines was approximately equal to the number of ________ | cytosines |
| How did scientist discover DNA? | The Griffith Experiment |
| ______________ connect complementary DNA strands | Hydrogen bonds |
| DNA is composed of nucleotides: | Adenine (A) binds to Thymine (T) - Guanine (G) binds to Cytosine (C) |
| Gene expression | The process by which DNA directs protein synthesis |
| Gene | a sequence of DNA that encodes a specific protein. Protein production occurs in two stages: - Transcription - Translation |
| Genes program protein synthesis via _________ in the form of messenger RNA | genetic messages |
| Cells are governed by a cellular chain of command | DNA → RNA → protein (This is the central dogma) |
| Transcription | produces an RNA molecule that’s complementary to DNA. It occurs in the nucleus |
| Translation | the information in RNA is used to make a protein. It occurs in the cytoplasm, the site is the ribosome. |
| The use of an RNA intermediate provides _________ for DNA and its genetic information | protection |
| Using an RNA intermediate allows more _______________________ to be made simultaneously | copies of the same protein |
| Three types of RNA interact to produce proteins: | - Messenger RNA (mRNA) - Ribosomal RNA (rRNA) - Transfer RNA (tRNA) |
| Transcription Uses DNA to ________ RNA | create |
| Transcription has three steps that happen at ribosomes: | - Initiation - Elongation - Termination and release |
| Initiation | RNA polymerase binds to the promoter, which is the beginning of the gene; enzymes unzip the DNA; the DNA template strand encodes the RNA molecule |
| Elongation | RNA polymerase moves along the template strand, making and RNA copy; the RNA molecule is complementary to the DNA template strand; the strands are antiparallel: new nucleotides add to the 3’ end of the RNA molecule; as it moves it untwists double helix |
| Transcription occurs at a rate of | 60 nucleotides/second |
| Termination | RNA polymerase reaches the terminator, which is the end of the gene; RNA, DNA, and RNA polymerase separate; DNA becomes a double helix again; the cell produced an RNA copy of a gene |
| RNA Is Processed in the Nucleus - splicing | Step 1 - Poly A tail and mRNA cap are added to the RNA. Step 2 - Introns are removed from the RNA molecule. Step 3 - The RNA then leaves the nucleus |
| codon | a three-nucleotide sequence that encodes one amino acid |
| Three stop codons: | UGA, UAG, UAA |
| Start codon: | AUG |
| Translation Builds the Protein | tRNA binds to an mRNA codon at the anticodon and binds to the corresponding amino acid |
| During initiation: | • Small ribosomal subunit binds to mRNA • Large ribosomal subunit binds • First tRNA molecule bind |
| Ribosomes | • Facilitate the specific coupling of tRNA anticodons with mRNA codons during protein synthesis • Made of large and small subunits Subunit= rRNA + protein |
| During elongation: | • The 2nd tRNA enters the ribosome next to the 1st tRNA • Amino acids covalently bond-1st tRNA leaves • The ribosome moves to the right, and a third tRNA comes in but the amino acids remain bonded together • This process continues and the protein grows |
| During termination: | • The ribosome reaches the stop codon • A release factor binds to stop codon • The polypeptide detaches from the mRNA and folds into a functional protein |
| Translation is __________ when multiple ribosomes attach to an mRNA molecule simultaneously. | efficient |
| Protein Synthesis Is Highly ____________ | Regulated |
| Gene regulation starts in the _________ | nucleus |
| Transcription can only occur if the correct ____________ factors are present. | transcription |
| Transcription factors | Proteins called transcription factors bind to nucleotide sequences called enhancers. A TATA binding protein binds to the promoter. Proteins (transcription factors) bind to nucleotide sequences (enhancers). A TATA binding protein binds to the promoter. |
| One gene can encode multiple proteins if different _______ are removed | introns |
| Gene regulation continues in the cytoplasm | Some mRNA may be degraded before it is translated into protein. Other mRNA may be silenced by microRNA, short sequences of nucleotides that bind to the mRNA and prevent translation. Proteins must be properly folded before they are functional |
| Sickle cell anemia | A single base substitution in a hemoglobin gene causes blood cells to form abnormally, leading to sickle cell disease. The mutant (sickle-cell) hemoglobin has a valine (Val) instead of a glutamic acid (Glu) |
| Cell division produces a continuous supply of _________________. Plays a role in cell repair | replacement cells |
| Cell division has a role in: | reproduction, growth, and development |
| During cell division, the genetic material DNA is _________ distributed between the two cells and it is passed along faithfully from one generation to the next | equally |
| Mitosis | the division of somatic cells |
| Meiosis | division of sex cells |
| Sex cells combine at fertilization to form | a zygote (2n) |
| Mitosis adds new cells while ____________ or “programmed cell death” removes them, allowing tissues to renew themselves. These two processes work together and balance each other. | apoptosis |
| What is the purpose of apoptosis? | regulate cell number |
| During cell division, each of the daughter cells must first replicate its __________, all of the cell’s genetic material. This process is called “DNA replication”. It is highly regulated, multistep process that is mediated by specific enzymes. | genome |
| Main enzymes: | 1. DNA Helicase 2. DNA polymerase 3. DNA ligase 4. Primase |
| Helicase | unwinds double helix |
| Binding proteins | stabilize each strand |
| Primase | adds short RNA primer to template strand |
| DNA polymerase | binds nucleotides to form new strands |
| Ligase | creates covalent bond between adjacent DNA segments |
| DNA replication step 1 | Enzymes called helicases unwind the DNA forming a “replication fork”; binding proteins hold the strands apart |
| DNA replication step 2 | Primase adds a short strand of RNA to the template strand |
| DNA replication step 3 | DNA polymerase creates a strand that is complementary to the template strand. DNA polymerase proofreads each new nucleotide added. If there is an incorrect pairing, the enzyme removes the wrong nucleotide and then resumes synthesis |
| DNA replication step 4 | Nucleotides added to the 3' end, Strand synthesis is continuous (leading strand), DNA polymerase adds nucleotides in the opposite direction from helicase movement. Strand synthesis is discontinuous (lagging strand) |
| DNA replication step 5 | An enzyme replaces the RNA primer with DNA, and ligases form covalent bonds between DNA segments; In prokaryotes, reproduction occurs by binary fission, an asexual process that replicates DNA and distributes it to two daughter cells. |
| Binary fission | division in half |
| Eukaryotic Cell Division | Eukaryotic cells do not divide by binary fission. Instead, they divide by mitosis. |
| DNA replication and protein synthesis occur when DNA is | loosely packed |
| Cell division or mitosis occurs when DNA has __________ into chromosomes (X-shaped structures) | condensed |
| Chromatin | DNA + histones |
| Nucleosomes | units of chromatin |
| Chromatin ___________ into bar-like bodies of chromosomes when the nucleus starts to divide or during cell division (mitosis) | condenses |
| Each chromosome is made of __ sister chromatids joined at a centromere | 2 |
| Human somatic cells (body cells) have | 46 chromosomes |
| Human gamete cells (sperm or eggs, that is sex cells) have one set of | 23 chromosomes |
| Epigenetics | the study of how your behaviors and environment can cause changes that affect the way your genes work |
| The cell cycle is | a collection of highly ordered processes that results in duplication of the cell |
| Cell cycle = | interphase + cell division |
| Cell division = | mitosis + cytokinesis |
| Mitosis = Cytokinesis = | nuclear division (division of the nucleus) division of the cytoplasm |
| Before cell division, we have ________ | interphase |
| Interphase has 3 phases: | G1 phase G0 phase S (synthetic) phase |
| G1 phase (first gap) | the cell grows and functions normally. Protein synthesis occurs (varies most in length) |
| G0 phase | the cell continues the function, but it does not replicate its DNA or divide. Most of your cells are currently in G0 |
| S (synthetic) phase | the DNA replicates (~10 hr, half the cycle |
| G2 phase | the cell produces proteins that are necessary for mitosis. DNA begins to wind more tightly around histones. Cells leaving G2 phase enter mitosis, the division of the nucleus, which is followed by cytokinesis, the division of the cell itself |
| Phases of mitosis: | prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis |
| Prophase | Chromosomes condense and become visible. Spindle forms as centrosomes move to opposite poles. |
| Prometaphase | Nuclear envelope breaks up. Spindle fibers attach to kinetochores on chromosomes. |
| Metaphase | Chromosomes align along equator of cell |
| Anaphase | Centromeres split as sister chromatids separate and move to opposite poles of cell |
| Telophase | Nuclear envelope and nucleolus form at each pole. Chromosomes decondense. Spindle disappears. |
| Cytokinesis | Division of the cytoplasm into two cells |
| In an animal cell, the first sign of cytokinesis is the: | cleavage furrow |
| Cancer cells: | • Do not respond normally to the body’s control mechanisms • Do not need growth factors • Divide indefinitely - immortal • Form tumors – benign or malignant (tumor is an abnormal mass of tissue) • Have the ability to spread - metastasis |
| Cancerous cells can _______ indefinitely and evade the cell cycle checkpoints | divide |
| A female parent contributes an _____, and a male parent produces _______. These sex cells fuse, yielding the first cell of the next generation | egg; sperm |
| Diploid cells | cells with two sets of chromosomes |
| Most cells in a sexually reproducing organism have two sets of chromosomes | one from the father and one from the mother |
| Autosomes | numbered chromosomes |
| Sex chromosomes | denoted by a letter |
| Male: | 44 + XY |
| Female: | 44 + XX |
| In human body cells, we have ___ pairs of autosomes and __ pair of sex chromosome | 22;1 |
| Each chromosome is paired with an __________ chromosome (except for when the X chromosome pairs with the smaller Y chromosome | equally-sized |
| The chromosomes of a homologous pair: | look alike and carry the same sequence of genes for the same traits |
| Deletion | piece of chromosome is lost (e.g., Cri du chat characterized by mental retardation, abnormal facial features and a cry like a cat) |
| Duplication | several repeats (e.g., Fragile X syndrome characterized by mental retardation) |
| Translocation | piece of chromosome move to another location—another environment! (e.g., Acute myelogenous leukemia) |
| Haploid cell | has only one set of 23 chromosomes |
| Zygote | the first cell of a new organism |
| When two haploid cells fuse at fertilization, one ___________ is formed | diploid zygote |
| Interphase | DNA replicates, Cell produces proteins needed for cell division |
| Prophase I (early) | Chromosomes condense and become visible |
| Prophase I (late) | Crossing over occurs, spindle forms, nuclear envelope breaks up |
| Metaphase I | Paired homologous chromosomes align along equator of cell |
| Anaphase I | Homologous chromosomes separate to opposite poles of cell; sister chromatids remain joined |
| Telophase I & Cytokinesis | Nuclear envelopes form around chromosomes, which may temporarily decondense. Spindle disappears. Cytokinesis may divide cell into two. |
| Prophase II | Spindles form. Nuclear envelopes break up. |
| Metaphase II | Chromosomes align along equator of cell |
| Anaphase II | Centromeres split as sister chromatids separate to opposite poles of cell |
| Telophase II & Cytokinesis | Nuclear envelopes assemble around daughter nuclei. Chromosomes decondense. Spindles disappear. Cytokinesis divides cells. |
| The gametes produced in meiosis are different from one another because of: | •crossing over (prophase I) •independent assortment (metaphase I) |
| During crossing over, two homologous chromosomes __________ genetic material during prophase I. | exchange |
| Meiosis occurs in ____________; mitosis occurs in __________ | germ cells; body cells |
| Nondisjunction in meiosis I produces: | gametes with either an extra or a missing chromosome |
| Down syndrome | An extra copy of a chromosome 21—a trisomy—causes genetic disorders |
| mRNA | encodes amino acid sequence |
| tRNA | physically links the "message" in mRNA to an amino acid |
| rRNA | combines with proteins to form ribosomes, the sites of protein assembly |
Created by:
coralis
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