ENTIRE GENETICS REVIEW

Genetics

The study of inheritance, which is the passing of traits from parents to offspring.

Complete Dominance

When only one of the alleles is expressed despite the presence of the other allele.

Phenotype

Refers to the observable trait (e.g., purple).

Incomplete Dominance

Neither allele is dominant; both traits result in partial expression (a blend of both).

Genotype

Refers to the alleles an organism contains for a particular trait (e.g., Pp).

Allele

A version of a gene.

Law of Segregation

When an organism makes gametes, each gamete receives just one gene copy, which is selected randomly.

Homozygous

A genotype in which the alleles of a gene are the same.

Codominance

Both alleles are expressed fully in heterozygotes; traits are NOT blended.

Heterozygous

A genotype in which the alleles of a gene are different.

Roan

A mix of intermingled red and white hair.

Truebreeding

Consistently producing offspring with only one form of a trait.

Law of Dominance

Any time the dominant allele is present, it will be expressed.

Monohybrid Cross

A cross that involves only one trait.

Hybrid

Heterozygous (Bb, Hh).

Pure

Homozygous (BB, HH).

Law of Independent Assortment

Genes for different traits are sorted separately from one another.

Recessive

An allele that is masked when a dominant allele is present.

Dominant

An allele that is always expressed.

Transcription

The process in the nucleus where a complementary mRNA strand is built from a DNA template.

Translation

The process at the ribosome where mRNA codes are 'read' to assemble amino acids into proteins.

Punnett Square

Diagram that can be used to predict the genotype and phenotype combinations of a genetic cross.

DNA Replication

The process of making a copy of DNA in interphase during S phase.

Uracil

Nitrogen base that pairs with adenine in RNA.

Adenine

Double ring purine. Nitrogenous base that pairs with Thymine in DNA.

Cytosine

Single ring pyrimidine. Nitrogenous base that pairs with Guanine in DNA.

Guanine

Double ring purine. Nitrogenous base that pairs with Cytosine in DNA.

Thymine

Single ring pyrimidine. Nitrogenous base that pairs with Adenine.

Purines

A nitrogenous base that has a double-ring structure; adenine or guanine.

Pyrimidines

A nitrogenous base that has a single-ring structure; thymine, cytosine, or uracil.

Friedrich Miescher

Credited with isolating 'nuclein' from the nuclei of white blood cells.

Phoebus Levene

Determined the 3 components that make up the basic building blocks of a nucleotide.

Joachim Hammerling

Determined that the nucleus contained the genetic material.

Erwin Chargaff

Determined Chargaff’s rules for base pairing: A=T and C=G.

Rosalind Franklin

Took the most important image ever taken of DNA, called photo 51.

Maurice Wilkins

Showed photo 51 to Watson without Rosalind’s permission.

Alfred Hershey & Martha Chase

Determined that DNA, and not protein, was the transforming principle.

James Watson & Francis Crick

Won the Nobel prize for their model of DNA in 1953.

Structure of DNA

Built of 2 strands made up of alternating phosphate groups & pentose sugars, with nitrogenous bases: A, T, G, & C.

Central Dogma of Biology

DNA → RNA → Protein.

Gene

A portion of a DNA molecule that carries information that helps to produce a particular trait.

Genome

All of the genetic material of an organism.

Coding DNA

Codes for genes (~2% of the human genome).

Non-coding DNA

Makes up the rest (~98%) & can play a role in regulating gene expression.

Codon

A group of 3 mRNA nucleotides that codes for a specific amino acid.

Genotyping

Looks at parts of DNA & common genetic variants (cheaper & easier to perform).

Genome Sequencing

Looks at entire sequence of DNA (expensive & harder to perform).

DNA (deoxyribonucleic acid)

A molecule that contains our genetic information.

Chromosome

A structure in the nucleus made of DNA & protein that carries genetic information.

Mitosis

A process that occurs in somatic cells where a single cell divides into 2 identical daughter cells.

Cell Cycle Phases

Includes Interphase (G1, S, G2), Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.

Meiosis

A process in which 4 haploid gametes are formed from 2 cell divisions.

Key Terminology for Meiosis

Includes Homologous chromosomes, Independent Assortment, Synapsis, and Crossing Over.

Gene Therapy

A technique used to treat or prevent diseases by altering genes in a person's cells.

Karyotype

An organized image of all 46 chromosomes from a cell, typically captured during metaphase.

Blood Types

Human blood type is both a codominant & dominant genetic trait.

Rh Factor

An inherited protein found on the surface of red blood cells.

Autosomes vs. Sex-linked Traits

Autosomal inheritance is controlled by alleles on autosomes; sex-linked is found on sex chromosomes.

Pedigrees

Diagrams that trace the inheritance of a certain trait among family members.

General Comparison of Meiosis & Mitosis

Mitosis produces identical cells; meiosis results in genetic diversity.