Chapter 7: Genes

Gametes

• In sexual reproduction, it involves the fusion of two specialized cells called ___ to form a new organism.

• This are haploid cells, meaning they contain only one set of chromosomes (n).

• In humans, ___ are sperm (from males) and egg cells (from females).

Zygote

• It’s the result when a sperm fertilizes and egg during fertilization.

• It’s diploid, containing two sets of chromosomes (2n), one set from each parent.

  • Male gamete (XY) (haploid-23 chromosomes): sperm, spermatozoon (spermatozoa)

  • Female gamete (XX) (haploid-23 chromosomes): egg, ovum (ova)

Genetics

• It’s the branch of biology that studies how traits are passed from one generation to the next.

• It explores the mechanism of inheritance, the variation of inherited traits, and the molecular basis of genes and their functions.

• By understanding it, we can unravel the mysteries of heredity and learn how organisms develop and evolve over time.

BT corn

• It’s also known as genetically modified corn or __ maize.

• A type of corn that has been genetically engineered to express proteins derived from the bacterium Bacillus thuringiensis (these proteins are toxic to certain insect pests, offering protection to the corn plants and reducing the need for chemical insecticides).

Selective Breeding

• Also known as artificial selection

• It has been practiced for centuries to enhance desirable traits in animals.

  • By selectively mating individuals with desirable characteristics, such as increased milk production, meat quality, or disease resistance, breeders can gradually improve the overall genetics of a population.

Genetic Engineering

• This techniques have enabled scientists to introduce specific genes into animals genomes to enhance desired traits.

  • ___ has been used to develop animals with improved disease resistance, enhanced growth rates, or increased production of valuable proteins, such as pharmaceuticals or enzymes.

Mendelian Inheritance

• These principles explain patterns of inheritance observed in traits controlled by single genes, such as ___ traits.

• It govern the transmission of traits from parents to offspring.

  • The principles of inheritance proposed by Gregor Mendel

  • such as dominance, segregation, and independent assortment.

Non-Mendelian Inheritance

• Many traits are influenced by multiple genes, environmental factors, and complex interactions.

• ___ ___ patterns, such as incomplete dominance, codominance, polygenic inheritance, and epistasis, contribute to the wide range of phenotypic variation observed in populations.

  • In addition to Mendelian inheritance

Gregor Mendel

• In 1856, Austrian monk noticed that the flowers of his pea plants were either violet or white, tall or short, etc.

• Based on his observations, he began to study heritable traits.

  • The study of genetics began long before scientists knew anything about DNA, chromosomes or alleles.

Traits

• Inherited through the transmission of genetic information from parents to offspring.

• The process of inheritance involves the passing on of genes, which are segments of DNA, from one generation to the next.

Genes

• Thread-like structures found in the nucleus of cells.

• It each contains instruction for specific traits, such as eye color, hair texture, or blood type.

  • located on chromosomes

Alleles

• This are where genes come from

• It may be dominant or recessive, meaning one ___ may mask the expression of another.

• One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

  • Ex: blue eyes and brown eyes

Meiosis

• A process during reproduction where gametes (sperm and egg cells) are formed.

• Each gamete receives only one copy of each chromosome, randomly selected from the parent’s two sets.

Homologous Chromosomes

• This are pairs of similar chromosomes.

Law of Segregation

• A law that explains why offspring inherit one allele from each parent for each gene.

Punnett square

• A graphical tool used to predict the possible outcomes of a genetic cross between two individuals.

• It was developed by Reginald Punnett.

• It’s particularly useful for understanding Mendelian inheritance patterns and determining the probabilities of different genotypes and phenotypes in offspring.

Law of Dominance

• A law that states heterozygote (an individual with two different alleles for a gene), one allele may mask the expression of the other allele, which is said to be recessive.

• It explains why certain traits are expressed in the offspring even when one parent carries the allele for that trait.

Dominant Alleles

• The allele that is expressed and determines the phenotype of the organism.

• This are expressed in the phenotype when present, even if only one copy is present in the genotype.

Recessive Alleles

• The allele that is not expressed in the presence of the dominant allele.

• This are expressed in the phenotype only when two copies are present in the genotype.

• This are masked by dominant alleles in heterozygous individuals.

Genotypes

• It refers to the genetic makeup of an organism, specifically the alleles present in its DNA for a particular trait or traits.

Phenotypes

• It refers to the observable characteristics or traits of an organism, which result from the interaction between its genotype and the environment.

Law of Independent Assortment

• This law explains the inheritance of traits that are controlled by genes located on different chromosomes.

• Alleles of different genes assort independently of each other during gamete formation.

• In other words, the inheritance of one trait is not influenced by the inheritance of another trait.

• Genes located on different chromosomes are inherited independently of each other.