Genetics Module 2

Genome

The complete set of DNA, including all of its genes, in an organism. It contains all the information necessary for the growth, development, and reproduction of that organism.

Types of Chromosomes

Metacentric

Sub-metacentric

Acrocentric

Telocentric

Metacentric

A type of chromosome where the centromere is located in the middle, resulting in two arms of equal length.

Sub-metacentric

A type of chromosome where the centromere is slightly off-center, resulting in one arm being longer than the other.

Acrocentric

A type of chromosome where the centromere is located closer to one end, resulting in one very short arm and one very long arm.

Telocentric

A type of chromosome where the centromere is located at one end, resulting in only one arm.

Chromosome # is based on

The # of centromeres

Centromere

The region of a chromosome where the two sister chromatids are joined, essential for proper segregation during cell division.

Chromatid

One half of a duplicated chromosome, which is connected to its sister chromatid at the centromere.

Telomere

The protective end of a chromosome that prevents deterioration or fusion with neighboring chromosomes, consisting of repetitive sequences.

Chromosome

A long, thread-like structure made of DNA and proteins that carries genetic information in the form of genes. During cell division, chromosomes are duplicated and segregated to daughter cells.

Haploid (n)

A cell or organism that has only one complete set of chromosomes, typically found in gametes such as sperm and egg cells.

Diploid (2n)

A cell or organism that contains two complete sets of chromosomes, one from each parent, typical of somatic cells in most organisms.

• Consists of homologs or homologous pairs

• Gene pairs

Homologs

Chromosome pairs, one from each parent, that are similar in shape, size, and gene content.

Homologous pairs

Chromosome pairs consisting of one homolog from each parent, similar in gene arrangement and size.

Chromosomes are made of…

DNA and proteins, forming a complex called chromatin that packages genetic material.

One, long, folded DNA molecule

Stabilized by histones

Solenoid

Scaffolding

Histones

Small proteins that help package DNA into nucleosomes, contributing to the structural organization of chromatin.

Chromatin

A complex of DNA and proteins that condenses to form chromosomes during cell division. It helps regulate gene expression and DNA replication.

Nucleosome

A structural unit of chromatin, consisting of a segment of DNA wrapped around a core of histone proteins, which helps in DNA packaging and regulation.

Octamer Core

A structure in nucleosomes composed of eight histone proteins that provides a scaffold for DNA wrapping.

Solenoid

A higher-order structure of chromatin formed by the coiling of nucleosomes, which aids in the further compaction of DNA within the nucleus.

Scaffolding

A structural framework that supports the organization and compaction of chromatin, facilitating the arrangement of nucleosomes and higher-order structures.

Supercoil

A secondary structure in DNA formed when the double helix is twisted beyond its normal state, allowing for increased compaction and organization within the chromosome.

Scaffold + Loops

Condensation

The process by which chromatin becomes more tightly packed and organized, enabling efficient DNA storage and regulation of gene expression.

Visual Chromosomal Landmarks

Number + Size

Heterochromatin patterns

Centromere location

Chromomeres

Telomeres

Banding patterns

Heterochromatin

A tightly packed form of DNA, associated with gene silencing, that appears as dark-staining regions in the nucleus. It plays a crucial role in maintaining chromosome stability and regulating gene expression.

Euchromatin

The less condensed form of chromatin, which is associated with active gene expression and transcription. It appears lighter-staining compared to heterochromatin under a microscope.

Centromere Location

The position of the centromere on a chromosome, which divides it into the short arm (p) and the long arm (q), and determines the chromosome's shape and behavior during cell division.

The # of Copies of Nucleolar Organizers (NO)

refers to the number of nucleolar organizer regions present on a chromosome, which are essential for ribosomal RNA synthesis and the formation of nucleoli. This number can influence the capacity for ribosome production within a cell.

Nucleoli

are cellular structures found within the nucleus, responsible for ribosomal RNA synthesis and the assembly of ribosomes. They are often located near the nucleolar organizer regions on chromosomes.

Banding patterns

are distinctive light and dark stripes observed on chromosomes when stained, aiding in their identification and analysis during cell division.

Polytene

chromosomes that are comprised of many identical chromatids, resulting from multiple rounds of DNA replication without cell division, commonly found in the salivary glands of certain insects.

Chromocenter

A region in the nucleus where multiple chromosomes aggregate, often containing heterochromatin, and plays a role in organizing the chromatin structure during cell division.

Puffs - swollen

regions on polytene chromosomes that are sites of active transcription, where localized chromatin decondensation occurs, allowing for gene expression.

Distended - Balbiani rings

regions of polytene chromosomes associated with active transcription, formed by the local swelling of the chromatin, facilitating RNA synthesis.

How many DNA per chromosome

Each chromosome typically contains one double-stranded DNA molecule that carries genetic information. During cell division, chromosomes are replicated, resulting in sister chromatids joined at the centromere.

Genes are …

Functional regions along the DNA that makes up a chromosome

Introns

non-coding sequences within a gene that are removed during RNA processing.

Exons

coding regions of genes that remain after introns are removed during RNA processing.

Transposable Elements

DNA sequences that can change their position within the genome, potentially affecting gene expression and genome structure.

Socrates

Greek philosopher known for his contributions to ethics and epistemology, often considered the father of Western philosophy.

Hippocrates

Ancient Greek physician often referred to as the "Father of Medicine." He is known for the Hippocratic Oath and his contributions to clinical medicine.

Aristotle

Greek philosopher and student of Plato, known for his works in metaphysics, ethics, politics, and sciences. He laid the foundation for many disciplines in Western thought.

Empedocles

Ancient Greek philosopher and scientist who proposed a theory of the four classical elements and is known for his work on the nature of change and the cosmos.

Romans

Mares could be fertilized by the wind

Middle Ages

Monstrous births

Spontaneous Generation

A historical theory that living organisms can arise from non-living matter, such as the belief that maggots could spontaneously generate from decaying meat.

Later disproved

Van Leeuwanhoek

A Dutch scientist known as the father of microbiology, he was the first to observe and describe microorganisms using a microscope he crafted.

William Harvey

An English physician who made significant contributions to the understanding of blood circulation, he is known for demonstrating how the heart pumps blood through the body.

Oscar Hertwig

A German zoologist who is best known for his work in embryology, particularly in demonstrating the mechanism of fertilization in sea urchins.

Camerarius

A German botanist known for his work on plant reproduction and the founder of the field of plant genetics.

Gene

Basic fundamental unit of heredity

Particulate inheritance

Characters (traits) are determined by discrete units that are inherited intact through the generations

Why did he study the Pea (scientifically)

He studied the pea plant because it has distinct traits, short generation time, and can be easily cross-pollinated, making it ideal for investigating the principles of inheritance.

Why did he study the Pea Plant (application to his situation)

They were food for them

Character

A heritable feature that varies among individuals

Also called property or trait

Lines

In genetics, lines refer to distinct varieties or strains of organisms that have been bred and maintained for specific traits or characteristics.

Pure Line

A genetically uniform lineage that consistently produces offspring with the same traits when self-fertilized.

Homozygous

Monohybrid Cross

A genetic cross between parents that differ in a single trait, resulting in offspring that show a 3:1 phenotypic ratio in the F2 generation.

P generation

The parental generation in a genetic cross, from which offspring are produced. This generation is typically used to demonstrate Mendelian inheritance patterns.

F1 generation

The first filial generation resulting from a cross between the P generation. The F1 generation typically exhibits dominant traits inherited from one or both parents.

F2 generation

The second generation of offspring produced from a monohybrid cross, typically showing a 1:2:1 genotypic ratio.

Hybrid

An organism that has two different alleles for a particular trait, resulting from a cross between individuals with differing traits.

Character forms or variants

Contrasting phenotypes for a character

Random Mating

The process where individuals pair by chance and without regard for their genotypes or phenotypes, promoting genetic variation in a population.

Self Cross

A breeding method where an organism is crossed with itself or its genetically identical clone to produce offspring.

Reciprocal Cross

A breeding experiment where two organisms are crossed in two different ways, allowing researchers to determine whether a trait is influenced by parental sex.

Back Cross

A breeding method where an offspring is crossed with one of its parents or an organism genetically similar to the parent, often used to maintain specific traits in a population.

Test Cross

A breeding experiment where an individual with an unknown genotype is crossed with a homozygous recessive individual. This technique is used to determine the genotype of the unknown individual based on the phenotypes of the offspring.

Mendel’s Experiment

A series of experiments conducted by Gregor Mendel in the 19th century to study the inheritance of traits in pea plants, establishing the foundational principles of genetics.

Why were there green peas in the F2 when all the F1 were yellow

The appearance of green peas in the F2 generation is due to the segregation of alleles. Mendel's experiments showed that the yellow allele is dominant over the green allele, allowing green peas to re-emerge when F1 hybrids are crossed.

1:3 phenotypic Ratio

The ratio of dominant to recessive phenotypes observed in the F2 generation, specifically showing that one out of four offspring exhibits the recessive phenotype when two heterozygous individuals are crossed.

1:2:1 Genotypic Ratio

The genotypic ratio resulting from a monohybrid cross between two heterozygous individuals, indicating that one-fourth of the offspring will be homozygous dominant, one-half will be heterozygous, and one-fourth will be homozygous recessive.

Backcrossing

The process of crossing a hybrid organism back with one of its parents or an individual genetically similar to its parents to achieve offspring with a desired genotype.

Law of Equal Segregation

The principle stating that alleles segregate equally during gamete formation, ensuring that each gamete receives one allele from each gene. This law is fundamental in understanding the inheritance patterns observed in Mendelian genetics.

Gametic Content

The genetic composition of gametes, which includes the alleles present for a specific gene in a given gamete, determined by the segregation of alleles during meiosis.

Random Fertilization

The process by which any sperm can fertilize any egg, resulting in a mix of genetic material in the offspring, contributing to genetic variation.

Law of Segregation

The principle that during the formation of gametes, the alleles for a trait separate so that each gamete carries only one allele for each gene. This foundational concept in genetics explains how traits are inherited.

Heterozygote

An individual with two different alleles for a particular gene, resulting in a genotype that is mixed, and often exhibits dominant traits.

Aa

Homozygote

An individual with two identical alleles for a specific gene, leading to a uniform genotype that typically reflects the traits of those alleles.

AA or aa

Homozygous Dominant

An organism that has two identical dominant alleles for a specific gene, resulting in a phenotype that expresses the dominant trait.

AA

Heterozygous Dominant

An organism with one dominant and one recessive allele for a specific gene, displaying the dominant phenotype despite having a mixed genotype.

Aa

Homozygous Recessive

An organism that carries two identical recessive alleles for a specific gene, leading to a phenotype that expresses the recessive trait.

aa

Predicting Progeny

The process of using genetic principles, such as Punnett squares, to estimate the possible genotypes and phenotypes of offspring produced from a specific mating.

Testcross

A breeding experiment used to determine the genotype of an individual exhibiting a dominant phenotype by crossing it with a homozygous recessive individual.

Gamete Formation

The process by which gametes (sperm and eggs) are produced through meiosis, resulting in the distribution of alleles to offspring.

Mitosis steps

Mitosis steps include prophase, metaphase, anaphase, and telophase, which ensure accurate chromosome segregation into daughter cells.

Prophase of Mitosis

The first stage of mitosis where chromosomes condense, the nuclear envelope breaks down, and spindle fibers begin to form, preparing for chromosome alignment.

Metaphase for Mitosis

The second stage of mitosis where chromosomes align in the center of the cell along the metaphase plate, ensuring proper segregation.

Anaphase for Mitosis

The third stage of mitosis where sister chromatids are pulled apart to opposite poles of the cell, ensuring each daughter cell receives an identical set of chromosomes.

Telophase for Mitosis

The final stage of mitosis where chromosomes de-condense, the nuclear envelope re-forms around each set of chromosomes, and the cell prepares to divide.

Prophase 1

The first stage of meiosis where homologous chromosomes pair up and exchange genetic material through crossing over, preparing for cell division.

Metaphase 1

The stage of meiosis where homologous chromosomes align at the metaphase plate, facilitating their separation during the next phase.

Anaphase 1

The stage of meiosis where homologous chromosomes are pulled apart to opposite poles of the cell, ensuring each daughter cell will receive one chromosome from each pair.

Telophase 1

The final stage of meiosis where the chromosomes reach the poles, nuclear membranes reform around each set, and the cell prepares to divide into two daughter cells.

Prophase 2

The stage of meiosis where chromosomes condense, the nuclear envelope breaks down, and spindle fibers form, preparing for the second meiotic division.

Metaphase 2

The stage of meiosis where chromosomes line up along the metaphase plate and spindle fibers attach to the centromeres, ensuring proper alignment and separation during the subsequent anaphase.

Anaphase 2

The stage of meiosis where sister chromatids are pulled apart towards opposite poles of the cell, ensuring each daughter cell will receive an identical set of chromosomes.

Telophase 2

The stage of meiosis where the separated chromatids reach opposite poles, the nuclear envelope reforms around each set of chromosomes, and the cells prepare to divide into four haploid gametes.

Dyad

A pair of sister chromatids joined by a centromere, present during meiosis.