Bio 30 Unit 1 flashcards

Chromosome Structure

• Chromosomes: DNA coiled around histone proteins then condensed.

Chromatin

• Chromatin: Uncoiled DNA present in interphase.

Centromere

• Centromere: The center of a chromosome that joins it to the spindle fiber.

Chromosomal Classification

Autosome

• Autosome: Chromosomes #1-22 that are not sex chromosomes.

Sex Chromosomes

• Sex Chromosomes: Chromosome #23; Females = XX, Males = XY.

Chromosome Similarities

• Homologous Chromosomes: Carry the same genes at the same locus (location). For example, Chromosome 1 and Chromosome 1.

Gene Definition

• Gene: Segment of DNA that codes for a specific trait.

Alleles

• Allele: Different forms of the same gene (Example: blue allele vs. brown allele).

Chromosome Count

Diploid Cells

• Diploid: 2n = total number of chromosomes in body cells; humans = 46.

Haploid Cells

• Haploid: n = number of chromosomes in gametes (sperm and eggs); humans = 23.

Cell Types

• Somatic Cells: Body cells.

Polyploidy

• Polyploidy: Organisms having greater than 2n chromosomes (common in plants).

Chromatid

• Chromatid: Half of a duplicated chromosome.

Duplicated/Replicated Chromosome

• A chromosome post-DNA synthesis.

Mitosis

• Mitosis: Cell division for growth, repair, and maintenance in somatic cells (phases: PMAT).

Meiosis

• Meiosis: Cell division for gamete production (sperm and eggs) occurring in gonads (ovaries and testes; phases: PMATPMAT).

Cell Cycle Phases

1. Interphase (G1, S, G2)

2. Mitosis (PMAT)

3. Cytokinesis (cell division).

Interphase Details

• Interphase: DNA exists as chromatin.

  • G1: Growth/protein synthesis.

  • S: DNA replication.

  • G2: Growth/protein synthesis.

Mitosis Phases

Prophase

• Prophase: Chromatin coils into chromosomes; centrioles move to poles; spindle fibers and asters form; nucleus and nucleolus disappear.

Metaphase

• Metaphase: Chromosomes line up at the metaphase plate.

Anaphase

• Anaphase: Centromeres divide, and chromatids move apart.

Telophase

• Telophase: Cleavage furrow forms, nuclear membrane reforms.

Cytokinesis

• Cytokinesis: The cell divides into two, with a cell plate forming in plant cells.

Cancer Cells

• Keep reproducing, can metastasize (move and grow in another part of the body), and do not specialize.

Metastasis

• The process by which cancer spreads.

Cloning

• Producing identical offspring from a single parent cell through asexual reproduction.

Cloning Steps

1. Remove nucleus from egg (enucleated).

2. Obtain DNA from donor and insert it into the egg.

3. Apply electric shock.

4. Zygote divides in vitro.

5. Blastocyst stage is inserted into a surrogate.

6. Identical offspring is formed.

Reproductive Strategies

Sexual Reproduction

• Requires male and female gametes; leads to variation.

Asexual Reproduction

• Involves one parent only (e.g., cloning, mitosis, parthenogenesis in reptiles).

Twinning

Identical Twins

• Clones with the same DNA from one sperm and one egg (monozygotic); usually share a placenta.

Fraternal Twins

• Not clones from two sperm and two eggs (dizygotic).

Stem Cells

• Totipotent Stem Cells: Can form a new organism.

• Cells capable of becoming many different cell types; used to repair damaged tissue.

Gametes

• Gametes: Sperm or eggs created by meiosis; haploid (n).

Synapsis

• Homologous chromosomes pair up during Prophase I to form a tetrad (4 chromatids).

Crossing Over

• Occurs during Prophase I when homologous chromosomes may exchange genetic material, more frequent between genes that are further apart.

Segregation

• Homologous chromosomes separate during Anaphase I or chromatids during Anaphase II.

Interphase I

• G1: Growth, protein synthesis. S: DNA replication. G2: Growth, protein synthesis.

Prophase I

• Synapsis occurs and crossing over may take place.

Metaphase I

• Tetrads line up in the middle on the metaphase plate.

Anaphase I

• Homologous pairs segregate to opposite poles.

Telophase I

• Cleavage furrow forms, with replicated chromosomes reaching the poles.

Prophase II

• Chromosomes can be seen; cells are haploid.

Metaphase II

• Chromosomes line up in the middle.

Anaphase II

• Centromeres split; single chromosomes move apart.

Telophase II

• Cleavage furrow forms; nuclear membrane and nucleolus reform.

Gametogenesis

• Gametogenesis: Creation of sperm and eggs.

Spermatogenesis

• Meiosis occurring in testes to create sperm.

Oogenesis

• Meiosis occurring in ovaries and fallopian tubes to create eggs (ova).

Fertilization

• When a sperm enters an egg, doubling the chromosome number; e.g., Human: Sperm (23) + Egg (23) = Zygote (46 chromosomes).

Sources of Variation

1. Gamete success

2. Crossing over

3. Independent assortment.

Independent Assortment

• The alignment of homologous pairs in Metaphase I is random.

DNA Summary

• DNA (DeoxyriboNucleic Acid): Genetic code for all living things; codes for proteins.

Location of DNA

1. Nucleus

2. Mitochondria (mtDNA) - inherited from mother

3. Chloroplast.

Rosalind Franklin

• Found that DNA is a helix, double-stranded, with a constant distance between strands.

Watson and Crick

• Discovered the 3-D structure of DNA.

DNA Structure

• Composed of 2 complementary strands (double helix).

  • Backbone: Deoxyribose sugar and phosphates.

  • Rungs: Nitrogen bases (A, T, C, G) connected with hydrogen bonds.

Semiconservative Replication

• New DNA comprises one parent strand and one daughter strand.

DNA Replication Steps

1. DNA untwists (helicase).

2. DNA unzips (helicase).

3. New nucleotides pair.

4. Sugar and phosphate molecules join (polymerase) to form two new DNA strands.

Human Genome Project

• Successfully sequenced all human genes; pros include treating disorders, while cons include possible genetic profiling issues.

RNA

• RNA: Single-stranded; ribose sugar with bases C, G, A, U.

  • Types:

    • mRNA: Copies DNA.

    • rRNA: Makes ribosomes.

    • tRNA: Carries amino acids to ribosome.

Protein Synthesis Overview

• Consists of transcription (in nucleus) and translation (at ribosome), occurring during G1 and G2 phases.

Transcription

• Process by which mRNA copies the DNA code and carries it to the ribosome.

Translation

• tRNA brings amino acids to mRNA on the ribosome to form an amino acid chain.

Triplet

• Set of 3 nitrogen bases on DNA that codes for one amino acid; also known as a codon.

Codon

• Set of 3 nitrogen bases on mRNA that codes for one amino acid.

Anticodon

• Set of 3 nitrogen bases on tRNA corresponding to a codon on mRNA, linking to an amino acid.

Peptide Bond

• Connection between amino acids in a chain.

Polypeptide

• Amino acid chain formed during protein synthesis.

Genetic Engineering

• Involves combining DNA from two organisms, referred to as recombinant DNA technology.

Recombinant DNA Process

1. Cut open plasmid with a restriction enzyme (R.E.).

2. Cut out the required gene with the same R.E.

3. Combine DNAs.

4. Add ligase to bond together.

5. Insert new plasmid into E. coli for replication.

6. Obtain the desired product (like insulin).

Restriction Enzyme

• Functions as scissors to cut DNA.

Ligase

• An enzyme that glues DNA segments together.

Plasmid

• A ring of DNA found in E. coli; utilized in recombinant DNA technology.

Gel Electrophoresis

• Separates segments of DNA.

  1. Ethanol is added to cells.

  2. DNA is spooled onto glass rod.

  3. R.E. is used to cut DNA.

  4. DNA is loaded into wells on electrophoresis plates.

  5. Current is applied; shorter fragments move farther than longer ones.

DNA Fingerprinting

• Uses gel electrophoresis to compare DNA from different individuals.

Mutations

• Changes in DNA, classified as chromosomal or point mutations.

Mutagenic Agents

• Causes of mutations, such as radiation or chemicals.

Chromosomal Mutations

• Changes in structure or number of chromosomes (e.g., Down’s syndrome involves 3 chromosomes of #21).

Karyotyping

• Pairs chromosomes based on size and banding pattern to detect chromosomal abnormalities, typically done using cells from the metaphase stage.

Ultrasound

• A medical imaging technique used to view internal organs or a fetus.

Amniocentesis

• A procedure utilizing a needle to withdraw amniotic fluid for analysis, often used for karyotyping or gel electrophoresis.

Chorionic Villus Sampling (CVS)

• Cells are drawn from the outer membrane of the embryo (chorion) as early as 8 weeks of pregnancy.

Nondisjunction

• Failure of chromosomes to divide properly during Anaphase I or II, affecting gamete outcomes.

Trisomy

• A condition of having 3 homologous chromosomes (e.g., Trisomy 21 is Down’s Syndrome).

Monosomy

• Having a single chromosome instead of a homologous pair (e.g., Turner’s syndrome is monosomy #23, leading to a female with one X chromosome).

Point Mutations

• Changes in 1-3 bases in the DNA strand during replication; types include substitution and frameshift mutations.

Substitution Mutations

• Involve switching 1 or 2 bases in the DNA strand, affecting only one triplet.

Frameshift Mutations

• Affect all downstream triplets; can result from deletion or addition of a base.

Societal Issues

• Concerns that impact individuals or societal groups.

Cultural Perspective

• Captures behaviors and beliefs characteristic of a specific group.

Economical Issues

• Financial matters related to concerns.

Ecological Issues

• Relate to the technological impacts on organisms and environments.

Ethical Issues

• Concerns regarding human conduct, focusing on the morality of actions and motives.