Notes

- DNA is called deoxyribonucleic acid
-double helix structure in which two polynucleotide chains twist to form a double helix structure. the sugar and phosphate are the backbones of the strands (outside the helix) while the nitrogenous bases are on the inside. Nucleotides are composed of phosphate, sugar, and a base.
- bases include, adenine, thymine, guanine, and cytosine. A-T , G-C - called complementary base pairs. The changes can occur due to genetic mutation and the complete DNA sequence is called a genome. The need for DNA replication is because every cells needs a set of instructions to follow for an organism to grow and reproduce, so the DNA replicates in a way that half of the strand is kept to the original one and the other half into a new one.

Cell cycle- takes place in a cell and leads the division and duplication and goes through checkpoints for accurate progression
G1- cell grows, synthezises proteins, makes sure DNA is ready to synthesis.
S- replication of DNA, makes sure daughter cells receive identical copy of genetic material.
G2- further growth and preperation and checks for errors.
Mitosis is a stage when the cell divides into two identical daughter cells.
prophase- chromatin condenses into chromosomes, nucleolus disappears, nucleus breaks down, spindle fibers form from centrosomes,
metaphase- the spindle fibers attach to the centromere of the chromosomes
anaphase- the spindle fibers pull the chromosomes to the opposite pole which splits into sister chromatids.
telophase- nucleus starts to form, spindle fibers break down
cytokinesis- cytoplasm divides resulting in two seperate daughter cells

Meiosis and mitosis-
The purpose of meiosis is that it occurs only in sexual reproduction and produces gametes with half the number of chromosomes and leads to genetic variation while mitosis occurs in asexual reproduction which produces two identical daughter cells with the same chromosome number as the parent cell. Meiosis involves two divisions, four haploid daughter cells while mitosis involves one, two diploid daughter cells. Mitosis doesn't have genetic material being exhanged with meiosis goes through a process called crossing over in which genetic material from a chromosome is being exchanged with another chromosome. Although, there may be some errors while exhanging information such as deletion, duplication, inversion and translocation. Deletion is when a part of the chromosome is deleted, duplication is when there are two or more segments of that chromosome appearing, inversion is when the chromosome has been inverted, and transolcation is when the chromosome was attached to a different part. Mitosis occurs in somatic cells while meiosis occurs in specialized cells within the reproductive organs.

Phenotype is the observable characteristics of an organism while genotype is the genetic makeup of the organism.
Domiance- in a cross between two pure breeds, the offspring will display the phenotype of the dominant trait in the F1 generation while the other trait will be masked.
Segregation- during gamete formation, two alleles seperate from each other so each gamete can carry an allele for each gene
Independent- inheritence of a particular allele is not affected by the inheritence of the other allele.
(how theres genetic variablity in meiosis) During Prophase I of meiosis, homologous chromosomes pair up and exchange segments of genetic material through a process called crossing over or genetic recombination. Crossing over occurs between non-sister chromatids of homologous chromosomes, resulting in the exchange of alleles between maternal and paternal chromosomes. This process leads to the creation of new combinations of alleles on chromosomes, increasing genetic variability among gametes.

Homologous chromosomes are a pair of chromosomes that have the same genes but may have different alleles (variants of a gene). One homologous chromosome is inherited from the individual's mother, while the other is inherited from the father.
During sexual reproduction, homologous chromosomes are passed from parent to offspring. Each pair of autosomes consists of homologous chromosomes.
Homologous chromosomes are similar in size, shape, and gene content, but they are not identical. They may carry different versions of genes, known as alleles, which can result in variations in traits among individuals.
Homologous chromosomes play a crucial role in processes such as meiosis, where they pair up and undergo genetic recombination (crossing over), leading to genetic diversity among offspring. They also ensure the faithful distribution of genetic material during cell division by aligning and segregating properly.