BSCI 150 Exam 3: Genetics and Cell Biology Concepts

Asexual Reproduction

Clones via mitosis/binary fission

Sexual Reproduction

Genetic diversity via meiosis + fertilization

Prokaryotes

Reproduce via binary fission

Eukaryotes

Reproduce via mitosis (somatic) / meiosis (gametes)

Cell Cycle Phases

G1 (growth) → S (DNA synth) → G2 (prep) → M (mitosis)

Cell Cycle Checkpoints

G1 (main), G2 (DNA integrity), M (spindle)

Cyclins/CDKs

Regulate phase transitions

Mitosis

2n→2n, 1 division, somatic cells

Meiosis

2n→n, 2 divisions, crossing over, gametes

DNA Structure

Double helix, A-T (2 H-bonds), C-G (3 H-bonds)

Chargaff's Rules

A=T, C=G

DNA Replication

Semi-conservative (Meselson-Stahl)

Helicase

Unwinds DNA

DNA Polymerase

Adds nucleotides

Ligase

Seals gaps

Telomerase

Extends chromosome ends

Point Mutation

Single base change

Frameshift Mutation

insertion or deletion

Silent Mutation

No AA change

Missense Mutation

AA change

Nonsense Mutation

Stop codon

Chromosomal Mutations

Del (loss) / Dup (copy) / Inv (flip) / Trans (move)

Mendel's Law of Segregation

Alleles separate

Punnett Square

Predicts offspring genotypes

Incomplete Dominance

Blending (e.g., pink flowers)

Codominance

Both traits expressed (e.g., blood types)

Transcription

DNA→mRNA (RNA pol)

Translation

mRNA→protein (ribosomes)

Start Codon

AUG (Met)

Stop Codons

UAA, UAG, UGA

Genetic Code

64 codons → 20 AAs (redundant)

Operons

Prokaryotes: lac operon = lactose metabolism

Epigenetics

Methylation/histone mod affect expression

Oncogenes

Activated → uncontrolled growth

Tumor Suppressors

Inactivated (e.g., p53, Rb)

PCR

Denature → Anneal → Extend (Taq polymerase)

CRISPR

Cas9 + guide RNA → gene editing

Key Experiments

Meselson-Stahl: semi-conservative replication

Avery/McLeod Experiment

DNA = transforming factor

Hershey-Chase Experiment

DNA (not protein) = genetic material

Mnemonic for Cell Cycle Phases

"Grow, Synthesize, Grow, Divide" (G1-S-G2-M)

Mnemonic for DNA Bases

"Apples in the Tree, Cars in the Garage" (A-T, C-G)

Central Dogma

"DNA makes RNA makes Protein"

Mitosis

A process of cell division that results in two identical daughter cells with the same number of chromosomes as the parent cell.

Meiosis I

The first division in meiosis, where homologous chromosomes are separated into two daughter cells, reducing the chromosome number by half.

Meiosis II

The second division in meiosis, similar to mitosis, where sister chromatids are separated into four haploid daughter cells.

Genetic Variation

The differences in DNA sequences among individuals, which can arise from processes such as crossing over and independent assortment during meiosis.

Aneuploidy

A condition in which there is an abnormal number of chromosomes in a cell, often resulting from nondisjunction.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to aneuploidy.

Pure Breeding

Organisms that produce offspring identical to themselves when self-fertilized.

Hybridization

The process of crossing two different pure breeding individuals to produce hybrid offspring.

Monohybrid Cross

A genetic cross between individuals that differ in one trait.

P Generation

The parental generation in a genetic cross.

F1 Generation

The first generation of offspring from a genetic cross.

F2 Generation

The second generation of offspring, produced by interbreeding the F1 generation.

Dominant

An allele that expresses its phenotype even in the presence of a recessive allele.

Recessive

An allele that only expresses its phenotype when two copies are present.

Heterozygous

An organism with two different alleles for a specific gene.

Homozygous

An organism with two identical alleles for a specific gene.

Genotype

The genetic makeup of an organism, representing the alleles it carries.

Phenotype

The observable characteristics or traits of an organism, determined by its genotype.

Gene

A segment of DNA that encodes a functional product, typically a protein.

Allele

A variant form of a gene that can exist at a specific locus on a chromosome.

Punnett Square

A diagram used to predict the outcome of a genetic cross by showing the possible combinations of alleles.

Testcross

A cross between an individual with an unknown genotype and a homozygous recessive individual to determine the genotype of the former.

Chromosomal Theory of Inheritance

The theory that genes are located on chromosomes and that the behavior of chromosomes during meiosis explains inheritance patterns.

Sex-linked Diseases

Diseases that are associated with genes located on sex chromosomes, often more common in males due to their single X chromosome.

Linked Genes

Genes that are located close together on the same chromosome and tend to be inherited together.

Transcription

The process of synthesizing RNA from a DNA template.

Translation

The process of synthesizing proteins from an mRNA template.

Mutation

A change in the DNA sequence that can lead to alterations in gene function or expression.

Germline Mutation

A mutation that occurs in the reproductive cells and can be passed to offspring.

Somatic Mutation

A mutation that occurs in non-reproductive cells and cannot be passed to offspring.

Point Mutation

A mutation that affects a single nucleotide in the DNA sequence.

Missense Mutation

A point mutation that results in a different amino acid being incorporated into a protein.

Nonsense Mutation

A point mutation that creates a premature stop codon in the protein coding sequence.

Induced Mutation

A mutation that results from exposure to external factors, such as chemicals or radiation.

Mutagen

An agent that causes changes to the DNA sequence, potentially leading to mutations.