Biology Exam 2

Allele

One of two or more alternate forms of a gene

Anaphase

Stage of mitosis in which the spindle pulls sister chromatids toward opposite poles of the cell

Antibody

Proteins that are produced normally by specialized B cells after stimulation by an antigen and act specifically against the antigen in an immune response

Antigen

Molecule that elicits an immune reaction

B Cell

Lymphocyte that has antigen-binding antibody molecules on the surface and secretes antibodies when mature

Carrier (3)

Individual possessing a specified gene and capable of transmitting it to offspring but not expressing or only weakly expressing its phenotype

Chimera

Individual, organ, or part consisting of tissues of diverse genetic constitution

Chromosome

Continuous molecule of DNA wrapped around protein in the

nucleus of cells

Codominance

Mode of inheritance in which two alleles are fully expressed in

a heterozygote

Codon

Triplet of RNA bases that specifies a particular amino acid

Crossing-over

Exchange of genetic material between homologous chromosomes during prophase I of meiosis

Cytokinesis

Distribution of cytoplasm into daughter cells in cell division

DNA

Genetic material consisting of a double helix of nucleotides

Dominant

Allele that is expressed whenever it is present

Endocrine

(1) Organ system that consists of glands and cells that secrete hormones. (2) Comparatively long distance signaling in organisms

Epithelial

Describes animal tissue consisting of tightly packed cells that form linings, coverings, and glands

Frameshift

Type of mutation in which nucleotides are added or deleted by any number other than three, altering the reading frame

Gene

Sequence of DNA that encodes a specific protein or RNA molecule

Gene Linkage

Relationship between genes on the same chromosome that causes them to be inherited together

Genome

All the genetic material in an organism

Genotype

Individual’s combination of alleles for a particular gene

Heterozygous

Possessing two different alleles for a particular gene

Homeostasis

Ability of an organism to maintain a stable internal environment despite changes in external environment

Homozygous

Possessing two identical alleles for a particular gene

Hormone

Biochemical synthesized in small quantities in one place and

transported to another as a way of sending a signal or message

Interphase

Stage preceding mitosis or meiosis, in which the cell grows and carries on its normal functions

Karyotype

Size-ordered chart of the chromosomes in a cell

Klinefelter syndrome

Abnormal condition in a male characterized by usually two X and one Y chromosomes, infertility, smallness of the testicles, sparse facial and body hair, and enlarged breasts

Liver

Organ that produces bile, synthesizes proteins and vitamins, stores glycogen, and monitors blood glucose level

Meiosis

Division of genetic material that halves the chromosome number and yields genetically variable gametes

Meristem

Localized region of active cell division in a plant

Metaphase

Stage in mitosis in which chromosomes are aligned down the center of the cell

mRNA

Molecule that carries a copy of the genetic information of the cell out of the nucleus so that it can be translated into proteins

Mutagen

Any external agent that causes a mutation

Nucleotide

Part of the prokaryotic cell where the DNA is located

Pancreas

Gland between the spleen and the small intestine that produces hormones, digestive enzymes, and bicarbonate

Pathogen

Something (such as a type of bacteria or a virus) that causes disease

Penetrance

Proportion of individuals of a particular genotype that express its phenotypic effect in a given environment

Phagocytosis

Engulfing and usually the destruction of particulate matter

Phenotype

Observable characteristic of an organism

Pili

Short projections made of protein on prokaryotic cells

Plasmid

Small circle of double-stranded DNA that is separate from a cell’s chromosome

Pleiotropy

Multiple phenotypic effects of one genotype

Prion

Infectious protein particle

Prophase

Stage of mitosis in which chromosomes condense and the mitotic spindle begins to form

Pseudopodia

Temporary protrusions or retractile processes of the cytoplasm of a cell that function (such as in an amoeba) especially in a locomotor or food gathering capacity

Recessive

Describes an allele whose expression is masked if a dominant allele is present

Ribosome

Structure made of RNA and protein that is the site of protein synthesis

RNA

Single-stranded nucleic acid

Short tandem repeat

DNA sequence consisting of a small sequence of bases that are repeated, which varies in size within a population

silent mutation

Change in DNA sequence that does not change the amino acid sequence when translated

Somatic

Describes one of the cells of the body that compose the tissues, organs, and parts of that individual other than the germ cells

Spindle fiber

Any of the apparent filaments constituting the structure that

separates chromosomes during mitosis

SRY

Gene for maleness found on the Y chromosome that has a key role in development of the testes and determination of sex.

Swyer syndrome

Condition characterized by male-to-female sex reversal in the presence of a normal 46XY karyotype; in individuals with this disorder the external genitalia is completely female

T cell

Lymphocyte that differentiates in the thymus, possesses highly specific cell-surface antigen receptors, and includes some that control the initiation or suppression of cell-mediated and humoral immunity

Telophase

Stage of mitosis in which chromosomes arrive at opposite poles and nuclear envelope forms

Testcross

Mating an individual of an unknown genotype to a homozygous recessive individual; the phenotypes of the offspring reveal the unknown genotype

Transcription

Production of RNA using DNA as a template.

Translation

Assembly of an amino acid chain based on the sequence of nucleotides in mRNA

Transposon

Piece of genetic material that can move from one place to another and change the functions of genes

tRNA

Molecule that is part of a ribosome and is involved in translating genetic information into proteins

Virus

Infectious agent that consists of genetic information enclosed

in a protein coat

Zygote

Fused egg and sperm that develops into a diploid individual.

Name and describe specialized components or adaptations of single-celled organisms

• Slime layer(prokaryote): sticky outer coat for attachment and protection.

• pili (prokaryote): hair-like projections for attaching to surfaces and for transferring DNA

• endospores (prokaryote): tough dormant structures that survive harsh conditions.

• flagella: whip-like tails for movement

• paramecium cell mouth (eukaryote): opening where food is taken in; cilia sweep food toward it

• amoeba pseudopodia (eukaryote): cytoplasm extensions for movement and engulfing food

• encystment(Amoeba): forms a protective cyst when conditions are poor

• colonial living

Using a labeled drawing and description, explain how gene transfer works in bacteria

Transformation: a cell takes up free DNA from its surroundings

Transduction: a virus accidentally carries DNA from one cell to another

Conjugation: a pilus connects two cells and a plasmid copy passed from donor to recipient

Draw, label, and describe the life cycle of a virus

1. Attachment: virus binds to a specific receptor on the host cell

2. entry: viral genome enters the cell

3. replication: host machinery copies viral genomes and makes viral proteins

4. assembly: new virions are put together

5. release: cell bursts or virions bud off

Name and describe the four tissue types in plants

• Meristematic: undivided, actively dividing cells at growth regions; source of all other tissues

• Dermal: outer protective covering

• Vascular: transport; xylem carries water and minerals, phloem

• Ground: everything else; photosynthesis, storage, support

Name and describe the four tissue types in animals

• epithelial: protection and storage; skin, mouth, esophagus

• connective: energy storage, insulation, connections, cushioning; ligaments, bones, joints, nearly everywhere

• muscle: movement; muscles

• nervous:communication; nerves, brain

Describe an example of how homeostasis works in humans

• Body temperature

  • body heats up

  • body detects it

  • sweating

  • temperature returns

Draw and label the human respiratory system

nasal cavity

pharynx

larynx

trachea

bronchi

bronchioles

alveoli

Name and describe mechanisms of innate immunity

• physcial barriers: skin, muscus, etc., keeps pathogens out

• phasgocytosis: white blood cells engulf and digest pathogens

• anti-pathogen toxins: chemicals that kill or inhibit microbes

• natural killer cells: detect infected cells and trigger cell death

Explain the difference between innate and adaptive immunity

• Innate: present from birth, fast, general (not pathogen-specific), no memory. Peaks early (NK cells, phagocytes).

• Adaptive: develops after exposure, slower, specific to a pathogen, builds memory (B and T cells). Peaks later.

• Both appear on the primary immune response timeline: innate first, adaptive later

Using a labeled drawing and description explain transcription

• Happens in the nucleus; DNA gene is the template.

• DNA unwinds and separates.

• RNA nucleotides pair with the DNA template (complementary).

• Uracil (not thymine) pairs with adenine.

• Product: mRNA that leaves to be translated.

Using a labeled drawing and description, explain the three steps of translation.

• Initiation: ribosome forms; chain starts at the start codon as tRNA matches mRNA (codon to anticodon).

• Elongation: mRNA moves to the next codon, matching tRNAs bring amino acids, and amino acids link.

• Termination: stop codon reached; no more amino acids added; ribosome disassembles and protein detaches.

• Several ribosomes can read one mRNA at once.

Name and describe the three stages of interphase.

• G1: 2n chromosomes uncoil so DNA can be used; normal cell functions; lasts hours to forever.

• S (synthesis): DNA replicated; still 2n, but copies stay joined as sister chromatids.

• G2: cell accumulates materials and resources for division.

Using a labeled drawing and description, explain what happens in each of the phases of mitosis

• Prophase: chromatin condenses into chromosomes; nuclear membrane disappears; spindle fibers form.

• Metaphase: spindle fibers line chromosomes up at the metaphase plate.

• Anaphase: spindle fibers contract, separating sister chromatids; each is now a chromosome.

• Telophase: membrane forms around each chromosome set; spindle disappears.

• Then cytokinesis splits the cytoplasm.

Describe two main ways meiosis differs from mitosis.

• Number of divisions/cells: mitosis makes 2 diploid cells in one division; meiosis makes 4 haploid cells in two divisions (meiosis I and II).

• Genetic variation: mitosis makes identical cells; meiosis has crossing over and independent assortment, so gametes differ.

Using a labeled drawing and description, explain how a testcross works

Goal: find an unknown genotype of an individual with the dominant phenotype (CC or Cc).

• Cross it with a homozygous recessive (cc).

• All offspring dominant -> unknown was CC.

• About 1:1 dominant:recessive -> unknown was Cc.

Explain how gene linkage can be used for gene mapping.

• Linked genes are on the same chromosome and tend to be inherited together.

• Crossing over can separate them.

• Genes far apart cross over more often; close genes less often.

• Recombination frequencies give relative distance (1% = 1 map unit), so genes can be ordered on a map.

Draw a Punnett square for a cross between two heterozygous codominant parents. The two alleles are R (red) and r (white). Tell what proportion has each genotype and phenotype.

• Genotypes: 1/4 RR : 1/2 Rr : 1/4 rr.

• Phenotypes: 1/4 red, 1/2 both red and white expressed together (heterozygote), 1/4 white.

Name the alleles for blood type. Explain how they relate to each other in terms of dominance. Give the genotypes for each blood type.

• Alleles: IA, IB, i (multiple alleles).

• IA and IB are codominant with each other; both are dominant over i.

• Type A: IAIA or IAi.

• Type B: IBIB or IBi.

• Type AB: IAIB.

• Type O: ii.

Explain why sons are more likely than daughters to be red-green colorblind.

• Males are XY: one X, so one recessive allele causes the trait (Y has no matching gene).

• Females are XX: need two recessive alleles; one normal allele makes them a carrier instead.

• Sons get their only X from the mother, so a carrier mother passes it to 1/2 of her sons.

Name and describe six different varieties of mutations

• Missense (base substitution): changes one amino acid.

• Nonsense: creates a premature stop codon (e.g., Duchenne muscular dystrophy).

• Frameshift: insertion/deletion of bases shifts the reading frame (e.g., Tay-Sachs).

• Triplet repeat expansion: 3-base sequence repeated many times (e.g., Huntington's).

• Chromosomal: large changes such as deletions, duplications, or extra chromosomes (e.g., trisomy 21).

• Silent: base change, same amino acid; no effect.

What is a chimera? How could a transposon create a chimera?

• A transposon is a mobile DNA segment ("jumping gene").

• If it jumps into or out of a gene (e.g., a pigment gene) in just some cells, those cells and their descendants differ from the rest, producing patches or variegation.