Biology Exam 2 Flashcards

A comprehensive set of flashcards covering key concepts related to biology, including genetics, cell division, DNA technology, and more.

Genome

The entire set of an organism’s DNA, including all of its genes.

Karyotype

A picture of all the chromosomes in a cell arranged by size and shape.

Diploid

A cell with two sets of chromosomes (2n), one from each parent.

Haploid

A cell with one set of chromosomes (n), such as sperm or egg cells.

Homologous chromosomes

Chromosome pairs that carry the same genes in the same order but may have different alleles.

Eukaryotic cell cycle stages

Interphase (G1, S, G2), Mitosis, and Cytokinesis.

Purpose of mitosis

To produce two identical diploid cells for growth, repair, and asexual reproduction.

Phases of mitosis

Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.

Sister chromatids

Identical copies of a chromosome.

Centromere

The region that joins sister chromatids.

Centrosomes

Structures that organize microtubules during cell division.

Spindle apparatus

The structure that pulls chromatids apart during mitosis.

CDKs

Cyclin-dependent kinases that control progression through cell cycle checkpoints.

Cell cycle checkpoints

G1 (DNA damage, size), G2 (DNA replication complete), M (chromosomes attached to spindle).

Positive regulators

Proteins that promote cycle progression (e.g., CDK-cyclin).

Negative regulators

Proteins that halt the cell cycle (e.g., p53, Rb).

Definition of cancer

Uncontrolled cell division due to failed regulation.

p53

A tumor-suppressor protein that halts the cycle when DNA is damaged.

Oncogene

A mutated gene that promotes uncontrolled cell growth.

Binary fission

A form of asexual reproduction in bacteria where the cell splits into two identical cells.

Purpose of meiosis

To produce haploid gametes for sexual reproduction.

Location of meiosis

Occurs in germ cells (ovaries and testes).

Prophase I

Chromosomes condense, homologs pair (synapsis), crossing over occurs.

Metaphase I

Homologous pairs align at the equator (independent assortment).

Anaphase I

Homologous chromosomes separate, sister chromatids remain together.

Telophase I and Cytokinesis

Two haploid cells form with duplicated chromosomes.

Meiosis II

Similar to mitosis—sister chromatids separate, resulting in four unique haploid cells.

Difference between meiosis and mitosis

Meiosis has two divisions, creates haploid gametes, and includes crossing over for genetic variation.

Ways meiosis generates variation

Crossing over and independent assortment.

Advantages of sexual reproduction

Increased genetic diversity and adaptability.

Homologous pairs in humans

23 pairs (46 chromosomes total).

Non-disjunction

Failure of chromosomes to separate, leading to abnormal chromosome numbers.

Gregor Mendel

A monk who studied inheritance using pea plants and discovered basic laws of genetics.

Mendel’s experimental method

Cross-pollination of pea plants and tracking traits over generations.

P, F1, and F2 generations

P = parents, F1 = hybrids showing dominant trait, F2 = 3:1 ratio of traits.

Gene

A segment of DNA that codes for a specific trait or protein.

Allele

Different versions of a gene.

Homozygous

Having two identical alleles for a trait.

Heterozygous

Having two different alleles for a trait.

Genotype

The genetic makeup of an organism.

Phenotype

The physical appearance of an organism.

Mendel’s Law of Segregation

Alleles separate during gamete formation so each gamete gets one allele.

Mendel’s Law of Independent Assortment

Genes for different traits are inherited independently if on different chromosomes.

Monohybrid cross

A cross for one trait showing a 3:1 phenotypic ratio.

Dihybrid cross

A cross for two traits showing a 9:3:3:1 phenotypic ratio.

Multiple alleles

More than two possible alleles for one gene.

Incomplete dominance

A blending of phenotypes.

Co-dominance

Both alleles fully expressed.

Sex-linked trait

A trait controlled by genes on the X chromosome.

Sex determination in humans

Females = XX, Males = XY.

Pedigree analysis

A diagram showing inheritance patterns across generations.

Inheritance types in pedigrees

Dominant = appears every generation; Recessive = skips; Sex-linked = mostly in males.

Pleiotropy

One gene affects multiple traits.

Epistasis

One gene masks or modifies another gene.

Structure of DNA

Double helix made of nucleotides held by hydrogen bonds.

Nucleotide components

Phosphate, deoxyribose sugar, and nitrogenous base.

DNA base pairing rules

A-T and C-G pairing.

Discoverers of DNA structure

Franklin (X-ray image), Watson and Crick (model).

Difference between RNA and DNA

RNA is single-stranded, uses ribose, and has uracil instead of thymine.

DNA replication

Copying DNA before cell division using DNA polymerase.

When and where does replication occur?

During S phase in the nucleus.

Outcome of DNA replication

Two identical DNA molecules.

Transcription

Making mRNA from a DNA gene.

RNA polymerase

The enzyme that synthesizes mRNA during transcription.

Promoter

DNA sequence that signals where transcription starts.

Termination sequence

DNA region signaling the end of transcription.

Introns and exons

Introns = noncoding; Exons = coding sequences joined to make mRNA.

Translation

Decoding mRNA into a protein on ribosomes.

Location of translation

On ribosomes in the cytoplasm.

Codon

Three mRNA bases coding for one amino acid.

Start and stop codons

Start = AUG; Stop = UAA, UAG, UGA.

mRNA and tRNA

mRNA carries the genetic code; tRNA brings the corresponding amino acids.

Genetic code

Universal codon set for amino acids; redundant due to multiple codons coding for the same amino acid.

Point mutations

Changes in a single DNA base pair.

Causes of mutations

Replication errors, radiation, and chemicals.

Substitution vs. insertion/deletion

Substitution = one base replaced; Insertion/deletion = frameshift affecting the entire amino acid sequence.

Silent mutation

A DNA change that doesn’t alter the protein sequence.

Gel electrophoresis

Technique that separates DNA fragments by size using an electric current.

How gel electrophoresis works

DNA moves toward positive end; smaller fragments move farther.

Uses of gel electrophoresis

DNA fingerprinting, mutation detection, genetic comparison.

PCR

Polymerase Chain Reaction, a method to amplify DNA segments.

Steps of PCR

Denaturation, Annealing, and Extension.

Usefulness of PCR

Amplifies tiny DNA samples for testing or forensic analysis.

Cloning

Producing genetically identical organisms from one source.

Cloning of Dolly the sheep

An adult cell nucleus was placed into an egg cell with no nucleus and implanted into a surrogate.

Implication of cloning

A nucleus from a body cell contains all the necessary genetic information.

GMO

Genetically Modified Organism, an organism with altered DNA for new traits.

Examples of GMOs

Bt corn, Golden rice, insulin-producing bacteria.

Positive aspects of GMOs

Higher yield, improved nutrition, pest resistance, and medical benefits.

Negative aspects of GMOs

Environmental impact, ethical issues, health uncertainties, and patents.

DNA technology in forensics

Uses DNA fingerprints and PCR to identify suspects or relatives.

DNA technology in medicine

Used for genetic testing, vaccines, gene therapy, and personalized medicine.