Introduction to Genetics and Heredity

A set of flashcards covering introductory genetics, Mendelian laws, terminology, history, and the chromosomal basis of heredity based on lecture module 1.

What two primary concepts does the branch of science called Genetics deal with?

Heredity (the transmission of traits from parents to offspring) and Variation (the differences among individuals of the same species).

What is a gene?

The fundamental unit of heredity; it is a specific sequence or segment of DNA that encodes a functional product such as a protein or RNA molecule.

Describe the Law of Dominance.

When an organism has two different versions of a gene (alleles), the dominant version will mask the expression of the recessive version.

What is the Law of Segregation?

An organism has two alleles for each trait but passes only one of these alleles to each of its offspring.

How many units of DNA make up the human genome, and into how many pairs of chromosomes are they packaged?

The human genome consists of $3,000,000,000$ units of DNA packaged into $23$ pairs of chromosomes.

In the metaphor of the genome as a book, what do chromosomes and DNA represent?

Chromosomes represent the chapters in the book, while DNA represents the words written across the pages.

What is the relationship between genes, RNA, and proteins?

The body makes a photocopy of a gene called RNA, which is then used to build biological building blocks called proteins.

What are the four types of DNA units?

$A$, $T$, $C$, and $G$.

How many genes are estimated to be in the human genome?

$20,000$-$25,000$ genes.

What is a mutation or pathogenic variant?

A mistake in your DNA that occurs and results in a detrimental outcome such as a disorder.

What did Hippocrates propose in his theory of pangenesis?

He proposed that \"seeds\" from all body parts are involved in heredity.

How many pea plants did Gregor Mendel experiment with between $1856$ and $1863$?

Approximately $28,000$ pea plants.

Who coined the term \"genetics\" and in what year?

William Bateson in $1905$ (also noted as $1906$ in supplementary PPT notes).

Which branch of genetics focuses on the transmission of traits across generations using Mendel’s laws?

Classical (Mendelian) genetics.

What does the field of Cytogenetics examine?

Chromosome structure, number, and abnormalities such as Down syndrome.

Define Epigenetics.

The study of heritable changes in gene expression that do not alter the actual DNA sequence.

What did the Theory of Pangenesis, as described by Aristotle and Darwin, suggest about semen?

That semen formed in every body part of the man and traveled via blood vessels to the reproductive organs.

What is the Germplasm Theory proposed by August Weismann ($1834$-$1914$)?

The theory that germplasm or sex cells perpetuate themselves through reproduction while somatoplasm is used for protection and reproduction of the germplasm.

Where is DNA primarily found in eukaryotic cells?

Within the nucleus, though smaller amounts are present in mitochondria and chloroplasts.

What type of proteins are involved in packaging DNA into highly organized chromosomes?

Histones.

What is the composition of the $46$ chromosomes normally found in humans?

$22$ pairs of autosomes and one pair of sex chromosomes ($XX$ or $XY$).

What is chromatin?

The complex of DNA and histone proteins found in the nucleus during interphase when the cell is not dividing.

What is a Locus?

The specific physical location of a gene or DNA sequence on a chromosome.

What are alleles?

Two or more alternative forms of a gene found at the same locus on homologous chromosomes.

What is the difference between a genotype and a phenotype?

Genotype is the specific genetic makeup or combination of alleles an organism possesses, while phenotype is the observable expression of that genotype.

What defines a heterozygous individual?

An individual that carries two different alleles for the same gene, such as $Aa$.

What is a zygote?

The first diploid ($2n$) cell formed after the fusion of two gametes (sperm and egg) during fertilization.

What is the difference between haploid ($n$) and diploid ($2n$) cells in humans?

Haploid cells, like gametes, contain $23$ chromosomes, while diploid cells, like somatic cells, contain $46$ chromosomes.

In chromosome anatomy, what are the names given to the short and long arms?

The short arms are called $p$ arms, and the long arms are called $q$ arms.

What happens during the S phase of Interphase in the cell cycle?

The cell duplicates each of its $46$ chromosomes.