Genetics - Complete In-Depth Biology Notes Flashcards

Comprehensive vocabulary flashcards covering basic genetic terms, Mendelian laws, monohybrid and dihybrid crosses, non-Mendelian inheritance, molecular genetics, mutation types, cell division, and population genetics based on the lecture notes.

Genetics

The branch of biology concerned with heredity, variation, the structure and function of genes, gene transmission, and changes in genetic material.

Heredity

The transmission of characteristics from parents to their offspring through genetic material.

Variation

Differences between individuals of the same species.

Gene

A section of DNA that contains information used to produce a functional product, usually a protein or functional RNA.

Locus

The specific physical position occupied by a gene on a chromosome (plural: loci).

Allele

An alternative form of a gene.

Chromosome

A long, organized structure consisting primarily of DNA associated with proteins that contains genes.

Homologous Chromosomes

A pair of chromosomes containing the same genes at corresponding loci, one coming from the biological mother and the other from the biological father.

Diploid

A cell containing two sets of chromosomes, represented by $2n$ ($2n = 46$ in normal human body cells).

Haploid

A cell containing one set of chromosomes, represented by $n$ ($n = 23$ in human gametes).

Gametes

Haploid reproductive cells (sperm in males, ovum/egg in females) produced through meiosis.

Genotype

The genetic constitution of an organism, particularly the alleles it possesses for a particular gene or set of genes.

Phenotype

The observable characteristics of an organism, influenced by both genotype and environment.

Homozygous

Having two identical alleles for a specific gene (e.g., $AA$ or $aa$).

Heterozygous

Having two different alleles for a specific gene (e.g., $Aa$); also called a hybrid in classical genetics.

Dominant Allele

An allele that is expressed in the phenotype when present in a heterozygous genotype under complete dominance.

Recessive Allele

An allele that is generally expressed only when there is no dominant allele present at that locus under complete dominance.

Genotypic Ratio

The ratio of different genotypes among offspring resulting from a genetic cross.

Phenotypic Ratio

The ratio of different observable phenotypes among offspring resulting from a genetic cross.

Law of Segregation

Mendel's First Law, stating that the two alleles of a gene separate during gamete formation so that each gamete receives only one allele.

Law of Independent Assortment

Mendel's Second Law, stating that alleles of different genes assort independently during gamete formation when on different chromosomes or far apart on the same chromosome.

Monohybrid Cross

A genetic cross examining inheritance involving one gene or characteristic.

Test Cross

A cross used to determine the genotype of an individual showing a dominant phenotype by crossing it with a homozygous recessive individual.

Back Cross

A cross between an offspring and one of its parents or an organism genetically similar to a parent.

Dihybrid Cross

A genetic cross that studies two characteristics simultaneously, yielding a classical phenotypic ratio of $9 : 3 : 3 : 1$ under independent assortment and complete dominance.

Incomplete Dominance

An inheritance pattern where neither allele completely masks the other, resulting in a heterozygote with an intermediate phenotype.

Codominance

An inheritance pattern in which both alleles are fully expressed in the heterozygote.

Multiple Alleles

A condition in which a gene has more than two possible alleles within a population.

ABO Blood Group System

A human blood group system determined by three major alleles ($I^A$, $I^B$, and $i$) demonstrating both codominance and complete dominance.

Sex-Linked Gene

A gene located on a sex chromosome, most commonly on the X chromosome.

Carrier

An individual who possesses a disease-associated recessive allele but does not express the condition because another allele masks it.

Autosome

A non-sex chromosome; humans have $22$ pairs ($44$ individual autosomes) in normal body cells.

Sex Chromosome

A chromosome involved in sex determination; human females typically have XX and males have XY.

DNA (Deoxyribonucleic Acid)

The major hereditary material in humans and many organisms, formed of nucleotides consisting of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

Complementary Base Pairing

The rule in DNA structure where Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

Semiconservative Replication

The mode of DNA replication where each resulting DNA molecule contains one original parental strand and one newly synthesized strand.

Transcription

The process of synthesizing an RNA molecule using a DNA strand as a template.

Translation

The process by which ribosomes use the information in mRNA to assemble a polypeptide chain.

Codon

A group of three consecutive bases on mRNA that specifies a particular amino acid or a stop signal.

Anticodon

A sequence of three bases on a tRNA molecule that pairs with a complementary codon on mRNA.

Mutagens

Environmental physical or chemical agents (such as radiation or chemicals) that increase mutation rates.

Frameshift Mutation

A gene mutation caused by insertions or deletions of nucleotides in numbers that are not multiples of three, altering the reading frame of downstream codons.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate normally during meiosis.

Down Syndrome

A genetic condition commonly caused by Trisomy 21 (having three copies of chromosome 21) resulting from meiotic nondisjunction.

Crossing Over

The exchange of corresponding DNA segments between non-sister chromatids of homologous chromosomes during Prophase I of meiosis.

Chiasmata

The physical points where crossing over occurs between non-sister chromatids during meiosis (singular: chiasma).

Mitosis vs Meiosis

Mitosis involves 1 division yielding 2 diploid somatic cells, whereas meiosis involves 2 divisions yielding 4 haploid gametes with halved chromosome numbers.

Polygenic Inheritance

An inheritance pattern where a characteristic is controlled by multiple genes, often showing continuous variation.

Continuous Variation

Variation in which characteristics show a continuous range of values rather than distinct categories (e.g., human height).

Discontinuous Variation

Variation in which individuals fall into distinct categories influenced by one or a small number of genes (e.g., ABO blood group).

Linked Genes

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

Pedigree Analysis

A diagrammatic representation showing the inheritance of a characteristic through a family across generations.

Autosomal Recessive Inheritance

An inheritance pattern requiring two recessive alleles ($aa$) to express the phenotype, where heterozygous carriers ($Aa$) pass the allele without expressing the condition.

Genetically Modified Organism (GMO)

An organism that has had its genetic material deliberately altered using biotechnology.

Recombinant DNA

DNA molecule formed by combining genetic material from different sources.

Gene Pool

The total collection of all alleles present in a population.

Allele Frequency

The proportion of copies of a particular allele in a population, where $p$ represents allele A and $q$ represents allele a ($p + q = 1$).

Hardy-Weinberg Principle

The principle stating that allele and genotype frequencies ($p^2 + 2pq + q^2 = 1$) remain constant across generations in an idealized non-evolving population.