Biology Keystone Exam Review: Anchor B.1 Section 1: Statement of Anchors, Anchor Descriptors, and Eligible Content

Section 2: Essential Vocabulary 1. 2. 3. 4. 5. 6. 7. 8. 9.

Allele A variation of a gene’s nucleotide sequence (an alternative form of a gene). Allele Frequency The measure of the relative frequency of an allele at a genetic locus in a population; expressed as a proportion or percentage. Asexual Reproduction A type of reproduction that involves generating two daughter cell clones from a single parental cell (i.e. mitosis, budding, and binary fission). Apoptosis Programmed cell death that results in the highly regulated break up of cellular compartments. Base Pair The nucleotides on complementary strands of nucleic acid that form hydrogen bonds with one another (DNA: A-T, C-G and RNA: A-U, C-G). Binary Fission A type of asexual reproduction seen in prokaryotic cell lineages. Cell Cycle The series of events that take place in a cell leading to its division and duplication. The main phases of the cell cycle are interphase, nuclear division, and cytokinesis. Centromere The region of two sister chromatids that remains intact, following replication. This region becomes separated during anaphase. Chromosomal Mutation A change in the structure of a chromosome (e.g., deletion, the loss of a segment of a chromosome and thus the loss of segment containing genes; duplication, when a segment of a chromosome is duplicated and thus displayed more than once on the chromosome; inversion, when a segment of a chromosome breaks off and reattaches in reverse order; and translocation, when a segment of one chromosome breaks off and attaches to a nonhomologous chromosome).

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Chromosomes A single piece of coiled DNA and associated proteins found in linear forms in the nucleus of eukaryotic cells and circular forms in the cytoplasm of prokaryotic cells; contains genes that encode traits. Each species has a characteristic number of chromosomes. Cloning A process in which a cell, cell product, or organism is copied from an original source (e.g., DNA cloning, the transfer of a DNA fragment from one organism to a self‐replicating genetic element such as a bacterial plasmid; reproductive cloning, the transfer of genetic material from the nucleus of a donor adult cell to an egg cell that has had its nucleus removed for the purpose of creating an embryo that can produce an exact genetic copy of the donor organism; or therapeutic cloning, the process of taking undifferentiated embryonic cells [STEM cells] for use in medical research). Conjugation A type of horizontal gene transfer that involves one prokaryotic cell directly giving genes to another prokaryotic cell. Crossing‐over An exchange of genetic material between homologous chromosomes during anaphase I of meiosis; contributes to the genetic variability in gametes and ultimately in offspring. Cytokinesis The final phase of a cell cycle resulting in the division of the cytoplasm. Deoxyribonucleic Acid (DNA) A biological macromolecule that encodes the genetic information for living organisms and is capable of self‐replication and the synthesis of ribonucleic acid (RNA). Differentiation The developmental process that involves a cell lineage’s function becoming increasingly specific. For example, when bone marrow cells develop into specific lymphocytes and/or red blood cells. Diploid A genetic state in which a cell has two copies of each chromosome, as in a eukaryotic somatic cell. DNA Replication The process in which DNA makes a duplicate copy of itself. Egg Cell The haploid female gamete produced by species that reproduce sexually. Embryology The branch of zoology studying the early development of living things. Fertilization The fusion of male and female gametes that results in the formation of a zygote. Frame‐shift Mutation The addition (insertion mutation) or removal (deletion mutation) of one or more nucleotides that is not divisible by three, therefore resulting in a completely different amino acid sequence than would be normal. Gamete A specialized cell (egg or sperm) used in sexual reproduction containing half the normal number of chromosomes of a somatic cell. Gene The location on a chromosome that contains a sequence of nucleotides that provides a blueprint for a specific hereditary trait. Gene Recombination A natural process in which a nucleic acid molecule (usually DNA but can be RNA) is broken and then joined to a different molecule; a result of crossing‐over. Genetics The scientific study of inheritance. Haploid A genetic state in which a cell only has a single copy of each chromosome. Gametes and prokaryotic cells are haploid, generally. Heterozygous A genetic condition wherein a diploid cell contains different alleles at the same gene region on homologous chromosomes. These alleles can either be dominant or recessive. Homologous Chromosome (Homolog) A chromosome that contains the same genes as another chromosome, but not necessarily the same alleles. For example- after fertilization, the zygote should have two copies of chromosome #2 (one copy from mom and one copy from dad). These

Biology Keystone Exam Review: Anchor B.1

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two chromosomes would be homologous, because they should both contain the gene for epilepsy. The alleles located at that gene region could be dominant or recessive, though. Homozygous A genetic condition wherein a diploid cell contains identical alleles at the same gene region on homologous chromosomes. These alleles can either both be dominant or recessive. Horizontal Gene Transfer Any process by which an organism acquires genes from non-inheritance mechanisms (i.e. transformation, transduction, conjugation). Inheritance The process in which genetic material is passed from parents to their offspring. Interphase The longest‐lasting phase of the cell cycle in which a cell performs the majority of its functions, such as preparing for nuclear division and cytokinesis. Meiosis A two‐phase nuclear division that results in the eventual production of gametes with half the normal number of chromosomes. Mitosis A nuclear division resulting in the production of two somatic cells having the same genetic complement as the original cell. Multiple Alleles More than two forms of a gene controlling the expression of a trait. Mutation A permanent transmissible change of genetic material (e.g., chromosomal mutations and gene mutations). Nondisjunction The process in which sister chromatids fail to separate during and after mitosis or meiosis. Nucleus A membrane‐bound organelle in eukaryotic cells functioning to maintain the integrity of the genetic material and, through the expression of that material, controlling and regulating cellular activities. Phenotype The physical characteristics of an organism or virus. These can include molecular, microscopic, or macroscopic traits. Point Mutation A single‐base substitution causing the replacement of a single‐base nucleotide with another nucleotide (e.g., silent mutation, in which there is no change in an amino acid; missense mutation, in which there is a different amino acid; and nonsense mutation, in which there is an insertion of a stop codon in the amino acid which stops protein synthesis). Polygenic Trait An aspect of the phenotype that is controlled by two or more genes at different locations on different chromosomes. Semiconservative Replication The process in which the DNA molecule uncoils and separates into two strands. Each original strand becomes a template on which a new strand is constructed, resulting in two DNA molecules identical to the original DNA molecule. Sister Chromatids The DNA structures that are generated by DNA replication. Unlike homologous chromosomes, sister chromatids should contain identical nucleotide sequences (unless a mutation has taken place during replication). Somatic Cell Any non-gametic cell that is part of an organism’s body (i.e. brain cells, leaf cells, etc). Sperm The haploid male gamete produced by species that reproduce sexually. Transduction A type of horizontal gene transfer that involved a viral intermediate. Transformation A type of horizontal gene transfer whereby cells acquire genes from their growth media. Translocation The process in which a segment of a chromosome breaks off and attaches to another chromosome. Zygote The single cell that results from the fusion of male and female gametes (sperm and egg, respectively).

Biology Keystone Exam Review: Anchor B.1 Section 3: A Description of Content Covered in this Assessment Anchor All living cells have a life cycle and reproduce. The cell cycle is the growth and division of cells, which will eventually make new cells. Mitosis is the process by which eukaryotic cells divide into two new identical daughter cells. Human body cells undergo mitosis to form new body cells. Single-celled organisms use mitosis to reproduce through asexual reproduction. There are four stages of the cell cycle – G1, S, G2 and Mitosis. G1, S, and G2 are the Interphase stages. The fourth stage, mitosis, is when actual division occurs. Interphase is the longest stage of the cell cycle. Stage G1 includes normal cell activity and growth. The cell doubles in size, and new organelles such as mitochondria, ribosomes, and centrioles are produced. Stage S is the stage during which DNA synthesis occurs. Each chromosome is replicated. After DNA replication, each chromosome consists of two identical sister chromatids held together by a central region called the centromere. Stage G2 is when the cell prepares for mitosis by making anything still needed for cell division (mitosis). Mitosis includes four phases. Prophase includes chromosomes condensing, centrioles (organelles which form microtubules) separating and moving to opposite poles. The nuclear membrane dissolves and nucleoli disappear. Spindle fibers attach themselves to each chromosome. In metaphase, the two centrioles are at opposite poles of the cell with the spindle spanning between them. The chromosomes line up in the middle of the cell at the metaphase plate. In anaphase the sister chromatids in each chromosome are pulled apart and begin to move toward opposite poles. Telophase concludes mitosis when the sister chromatids have been pulled apart so that one copy of each chromosome is at one end of the cell and another copy is at the other end. The spindle apparatus disappears and the nuclear membrane reforms around each set of chromosomes and thenucleoli reappear. The chromosomes then uncoil and cytokinesis occurs. Cytokinesis is when the cytoplasm and all the organelles of the cell are divided as the plasma membrane pinches inward and the two newly formed daughter cells separate from each other.

Biology Keystone Exam Review: Anchor B.1 Meiosis is the form of cell division that produces four cells, each with half as many chromosomes as the parent cell. Meiosis occurs in sex cells (gametes) of organisms that reproduce sexually. Haploid cells are cells that have one copy of each chromosome. Gametes (sperm and egg) are haploid. The human haploid number is 23 chromosomes. Diploid cells are cells that have two copies of each chromosome. Somatic cells (body cells) are diploid. When a sperm (haploid) fertilizes an egg (haploid), the resulting zygote is diploid. The human diploid number is 46 chromosomes. Like mitosis, meiosis includes interphase during which the chromosomes replicate. The cell then goes through two divisions as follows: Meiosis I: 

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Prophase I – The replicated chromosomes condense and homologues pair up in a process called synapsis. Crossing over occurs. Crossing over is the exchange of genetic material between homologous chromosomes. Metaphase I – Homologous pairs line up in the middle of the cell. Anaphase I – Homologous pairs separate and move to the poles. Telophase I – Each pole now has a haploid chromosome set. Telophase I occurs simultaneously with cytokinesis and two cells are formed.

Meiosis II (similar to Mitosis):    

Prophase II – A spindle apparatus forms and the chromosomes condense. Metaphase II – Sister chromatids line up in the center of the cell Anaphase II – The sister chromatids separate and move to opposite poles. Telophase II – The nuclear membrane reforms and cytokinesis occurs resulting in 4 genetically different haploid cells.

Nondisjunction is the process in which homologous chromosomes or sister chromatids fail to separate during meiosis. Nondisjunction can occur in anaphase of meiosis I or II, resulting in gametes with abnormal numbers of chromosomes. Ex: Down Syndrome – people with Down Syndrome have an extra copy of chromosome 21.

Biology Keystone Exam Review: Anchor B.1 DNA replication is the molecular mechanism of inheritance. DNA replication occurs during the S phase of mitosis or meiosis. DNA is a polymer made from building blocks called nucleotides strung together. Each nucleotide consists of a phosphate group, a 5-carbon sugar and a nitrogenous base. There are 4 nitrogenous bases: adenine (A), guanine (G), thymine (T), and cytosine (C). DNA is a double-helix – It contains 2 strands of DNA bonded together that run in opposite directions. The DNA double-helix has the sugarphosphate backbones on the outside of the double helix and the nitrogenous bases on the inside. The two strands of DNA are bound together by hydrogen bonds between the bases of the nucleotides. Due to their molecular structure, A allows pair with T, C allows pairs with G. This is called complementary base pairing. DNA replication is semi-conservative because one old strand of DNA is maintained (conserved) while a new strand is made from the template of the old strand. During replication, the double helix separates and each DNA strand serves as a template for a new DNA strand. The new strand is built by adding the complementary nucleotide (using base pairing rules) to the existing template strand. Genetic information is conserved during replication because the base pairing rules ensure that the new DNA is an exact copy of the original DNA. The genetic code is contained in the specific order of the four base pairs in DNA.

Basic rules of gene transmission and expression:  

Genes are elements of DNA that are responsible for observed traits. In eukaryotes, genes are found in large linear chromosomes.

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A chromosome is very long continuous DNA double-helix. Humans have 23 pairs of chromosomes in somatic (body) cells. Each pair of chromosomes represents homologous chromosomes (one from mom and one from dad). Diploid organisms (like humans) have two copies of each chromosome and, therefore, 2 copies of each gene. Each gene has a specific location on a chromosome. The two copies of each gene can have a different nucleotide sequence in an organism. These different versions of a gene are called alleles. Ex. – Attached (f) and free earlobes (F) are different alleles of a gene. o Homozygous individual – has two copies (two alleles) of a gene that are identical. Ex. – FF o Heterozygous individual – has two different alleles for a gene. Ex – Ff An organism’s genotype is the type of alleles is has (its genetic composition). An organism’s phenotype is the appearance and physical expression of its genes.

Section 4: Phelan Sections that support this Assessment Anchor 2.20, 5.2, 5.3, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 6.10, 6.11, 6.12, 6.14, 13.4, 14.10, 14.11, 14.12, 18.2, 18.3, 18.5, 18.6, 18.8, 18.10, 18.12, 18.13, 24.10, 25.4, 25.6, 25.8, 25.11, 25.12 Section 5: Sample Questions

Biology Keystone Exam Review: Anchor B.1

Biology Keystone Exam Review: Anchor B.1

Section 6: Online video resources for review Google “Bozeman Science” and click on the “Biology” link. Check out the following videos: Cells     

Cancer – What is it? Cell Division Diploid vs Haploid Meiosis and Phases of Meiosis Mitosis and Phases of Mitosis

Genetics         

Cell Cycle, Mitosis & Meiosis Chromosomal Inheritance DNA & RNA Part 1 and 2 DNA Replication Genotypes and Phenotypes Mechanisms the Increase Genetic Variation Mutations What is DNA? What are Chromosomes?

Google “Khan Academy Biology” and click on the “Cells” link. Check out the following video: 

Chromosomes, Chromatids, Chromatin, etc.

Biology Keystone Exam Review: Anchor B.1 Back at the main page of “Khan Academy Biology” click on the “Cell Division” link. Check out the following videos:      

Fertilization terminology: gametes, zygotes, haploid, and diploid Zygote differentiating into somatic and germ cells Phases of mitosis Phases of meiosis Embryonic Stem Cells Cancer

Back at the main page of “Khan Academy Biology” click on the “Heredity and Genetics” link. Check out the following videos:  

Introduction to heredity Genetics 101: Parts 1 through 4

Back at the main page of “Khan Academy Biology” click on the “Crash Course Biology” link. Check out the following videos:     

Heredity DNA structure and replication DNA, hot pockets, & the longest word ever Mitosis: Splitting up is complicated Meiosis: Where the sex starts