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Cell Division

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Reproduction of a cell; Two "daughter" cells that result are genetically identical to each other and to the original "parent" cell.

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Chromosomes

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Structures that contain most of the cell's DNA.

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Asexual Reproduction

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Does not involve fertilization of the egg by sperm; offspring are genetic duplicates of their single parent

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Sexual Reproduction

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Requires fertilization of the egg by sperm; produces unique offspring

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Gametes

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Reproductive cells (egg/sperm); requires meiosis

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Chromatin

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Makes up chromosomes; fibers composed of roughly equal amounts of DNA and protein molecules

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Histones

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A small protein molecule associated with DNA and important in DNA packing in the eukaryotic chromosome

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Nucleosome

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The bead-like unit of DNA packing in a eukaryotic cell; consists of DNA wound around a protein core made up of eight histone molecules

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Sister chromatids

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Two identical parts of a duplicated chromosome. While joined, two sister chromatids make up one chromosome; eventually separated during mitosis or meiosis II

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Centromere

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The region of a chromosome where sister chromatids are joined and where spindle microtubules attach during mitosis and meiosis; divides at the onset of anaphase during mitosis and anaphase II of meiosis

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Cell Cycle

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Ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division into two cells

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Interphase

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Time where cell goes about its usual business, performing its normal functions within the organism; Cell is here 90% of the time

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Mitotic (M) Phase

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Part of the cell cycle when the cell is actually dividing; includes mitosis and cytokinesis

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Mitosis

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Nucleus and its contents (especially the duplicated chromosomes) divide and are evenly distributed, forming two daughter nuclei.

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Cytokinesis

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Where the cytoplasm (and all the organelles) is divided in two.

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Functions of Cell Division by Mitosis

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1. Cell Replacement 2. Growth (Cell division) 3. Asexual Reproduction

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G1 Phase

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Each chromosome is single and the cell performs its normal functions

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G2 Phase

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Each chromosome in the cell consists of two identical sister chromatids, and the cell prepares to divide

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S Phase

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Chromosome duplication; DNA synthesis (DNA is precisely doubled)

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Prophase

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Chromatin fibers coil, existing as two identical sister chromatids joined at the centromere; mitotic spindle begins to form. Late prophase - nuclear envelope fragments; spindle tracks attach to the centromeres of the chromosomes and move them (the chromosomes) toward the center of the cell

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Metaphase

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Mitotic spindle is fully formed; the centromeres of all chromosomes line up between the two poles of the spindle; the spindle pulls at the centromeres

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Anaphase

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Sister chromatids of each chromosome separates into daughter chromosomes, moving towards opposite poles of the cell as the spindle fibers shorten.

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Telophase

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Two groups of chromosomes have reached opposite ends of the cell. Considered as the reverse of prophase; nuclear envelopes form, the chromosomes uncoil, and spindle fibers disappear.

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Somatic Cell

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A typical body cell; Any cell in a multicellular organism except a sperm or egg cell or a cell that develops into a sperm or egg

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Karyotype

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A display of micrographs of the metaphase chromosomes of a cell, arranged by size and centromere position

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Homologous Chromosomes

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Two chromosomes of a matching pair carrying genes controlling the same inherited characteristics

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Sex Chromosomes

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Chromosomes that determine a person's sex (gender); Males have one X and one Y chromosome, females have two X chromosomes.

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Autosomes

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A chromosome not directly involved in determining the sex of an organism

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Diploid

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Containing two sets of chromosomes in each cell, one set inherited from each parent; referring to a 2n cell (46 in humans)

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Haploid

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A cell with a single chromosome set; only has one member of each pair of homologous chromosomes; n cell (23 in humans)

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Meiosis

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Process of cell division that produces haploid gametes in diploid organisms, where the number of chromosomes are half of that in mitosis and the exchange of genetic material (Crossing over)

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Nondisjunction

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Members of a chromosome pair fails to separate at anaphase and can occur during meiosis I or II. Results in abnormal numbers of chromosomes.

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Heredity

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Transmission of traits from one generation to the next

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Genetics

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Science of heredity; founded by Gregor Mendel (1860s)

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Character

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A heritable feature that varies among individuals

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Traits

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Each variant of a character

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Hybrids

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Offspring of two different purebred varieties

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Cross

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Cross fertilization between the offspring and the parent organisms

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P Generation

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Parental generation

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F1 Generation

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F = filial; Hybrid offspring

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F2 Generation

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When F1 plants self-fertilize or fertilize each other to produce offspring

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Mendel's Law of Segregation

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A sperm or egg carries only one allele for each inherited character because the two alleles for a character segregate (separate) from each other during the production of gametes

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Alleles

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Alternative versions of genes that account for variations in inherited characters

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Homozygous

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An organism that has two identical alleles for a gene

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Heterozygous

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An organism that has two different alleles for a gene

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Dominant Allele

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Allele that determines the organism's appearance if two inherited alleles differ

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Recessive Allele

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Allele that has no noticeable effect on the organism's appearance if two inherited alleles differ

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Phenotype

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An organism's physical appearance

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Genotype

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An organism's genetic makeup

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Mendel's Law of Independent Assortment

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Each pair of alleles separate independently of the other pairs of alleles during gamete formation; the inheritance of one character has no effect on the inheritance of another

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Dihybrid Cross

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Mating of parental varieties differing in two characters

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Testcross

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A mating between an individual of dominant phenotype but unknown genotype and a recessive individual

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Rule of multiplication

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A rule stating that the probability of a compound event is the product of the separate probabilities of the independent events

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Wild-Type Traits

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The trait most commonly found in nature

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Pedigree

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A family tree representing the occurrence of heritable traits in parents and offspring across a number of generations

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Carriers

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Heterozygous parents that have a recessive allele that can create a disorder, but appear normal themselves; Example: Color-blindness

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Incomplete Dominance

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Characters where the phenotype of the offspring falls between the phenotypes of the parents

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ABO Blood Groups

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Genetically determined classes of human blood that are based on the presence or absence of carbohydrates A and B on the surface of red blood cells; Phenotypes = A, B, AB, and O.

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Codominant

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Where two alleles are expressed in heterozygous individuals; Example: An individual with blood type AB

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Pleiotropy

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One gene influences several characters

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Polygenic inheritance

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Opposite of Pleiotropy; Effects of two or more genes on one phenotypic character

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Epigenetic inheritance

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The transmission of traits by mechanisms not directly involving DNA sequence

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Chromosome Theory of Inheritance

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States that genes are located at specific positions on chromosomes and that the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns

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Loci (Locus)

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Location of a gene on a chromosome

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Linked Genes

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Genes located near each other on the same chromosome

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Sex-Linked Gene

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A gene located on a sex chromosome

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Lethal Allele

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Genetic mutation where if in its homozygous dominant form, it results in death; alters genotype ratio

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Molecular Biology

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The study of heredity at the molecular level

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Nucleotides

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Consists of a phosphate group, a sugar group, and a nitrogenous base; In DNA, there is Adenine, Thymine, Cytosine, and Guanine. In RNA, Uracil replaces Thymine

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DNA Strand

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Consists of two polynucleotide strands kept together by hydrogen bonds

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DNA Replication

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Ensures that all body cells in a multicellular organism carry the same genetic information

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DNA polymerase

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Enzyme found in the cell nucleus; Breaks hydrogen bonds and separates DNA strands in 2, attaches correct nucleotide sequence to the unpaired end, then creates 2 identical strands of DNA

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Transcription

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Transfer of genetic information from DNA into an RNA molecule

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Translation

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Transfer of the information from RNA into a polypeptide (Protein)

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DNA

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Master copy of genes; stays in nucleus

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RNA

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Single stranded polynucleotide that provides instructions for making a protein

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Ribosomes

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Translates information from RNA into a protein

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Codons

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Nitrogenous bases arranged in triplet codes to indicate a specific amino acid; flow of protein synthesis relies on this

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RNA Polymerase

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Responsible for splitting DNA strands and creating an RNA strand

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Transcription - Initiation

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RNA polymerase attaches to promoter sequence of DNA

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Transcription - Elongation

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RNA polymerase stretches across DNA to elongate RNA

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Transcription - Termination

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RNA reaches a stop codon (Terminator) sequence; RNA molecule and RNA polymerase detach

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Introns

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Non-coding sequences of RNA ('junk DNA')

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Exons

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Coding sequences of DNA

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RNA Splicing

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Enzymes splice out introns and glue together enzymes; creates mRNA

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tRNA

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Transfer RNA; Holds an anticodon at one end to read codons in RNA and an amino acid at the opposite end; there is a separate tRNA molecule for each amino acid

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rRNA

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Ribosomes; Protein makers; there's a small subunit that holds the mRNA chain and a large subunit to hold tRNA

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P-Site

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Part of rRNA's large subunit that holds the growing protein

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A-Site

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Holds tRNA with next amino acid in sequence

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Translation - Initiation

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mRNA binds to small subunit of ribosome > initiator tRNA binds to start codon of mRNA > Large ribosomal subunit binds on to small subunit and puts tRNA in the P-Site

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Translation - Elongation

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*Codon recognition; tRNA with the next anticodon sequence binds at the A-site > *Peptide bond formation; ribosome moves the polypeptide from the P-site to the A-site, joining the new amino acid to chain > *translocation; ribosome kicks out used tRNA from P-site ; A-site tRNA is translated from A-site to P-site > Process repeats until 'stop' codon is reached

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Translation - Termination

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Once the 'stop' codon is reached, the ribosome essentially 'self-destructs'

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Mutation

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Any change in the nucleotide sequence of a cell's DNA and often only occurs in one nitrogenous base; source of evolution/different alleles needed for genetic research

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Nucleotide substitution

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Replacement of one nucleotide and partner with another; could be no change in amino acid because multiple codons code for the same amino acid; sometimes there's a big change (Example: Sickle cell anemia)

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Nucleotide deletion

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If nucleotide is deleted, codons from that point on are misread; likely to be completely nonfunctional

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Nucleotide insertion

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disrupts all codons that follow; also most likely to produce a nonfunctional polypeptide

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Mutagens

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Other sources of mutation that are physical or chemical agents; most can act as carcinogens

BIO 100 Unit 2 – Genetics – Flashcards

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