science reproduction unit

what are the three components of the cell theory

All living things are made of cells.

The cell is the basic unit of life.

All cells come from pre-existing cells.

What are organelles?

Specialized structures within a cell that perform specific functions.

what are Prokaryotic Cells?

No nucleus, simple, smaller (e.g., bacteria).

what are eukaryotic cells?

Has a nucleus, complex, larger (e.g., plant & animal cells).

what is the structure of a nucleus

Contains chromatin (DNA + proteins), surrounded by a nuclear membrane.

how does a nucleus function?

Controls cell activities, stores genetic material (DNA).

What is the nucleolus?

A small dense region in the nucleus that makes ribosomes.

Structure of DNA

Double helix shape.

Sugar-phosphate backbone (sides of the ladder).

Nitrogenous bases (steps/rungs): A-T, C-G (Base Pair Rule).

What is a nucleotide?

The building block of DNA (sugar + phosphate + base).

Different forms of DNA

Uncoiled double helix (in non-dividing cells).

Chromatin (loosely packed DNA).

Chromosomes (tightly packed DNA, visible during cell division).

what is a Karyotype

A visual representation of chromosomes in a cell.

how many chromosomes are in Human Cells

46 chromosomes

how many chromosomes are in Somatic (body) cells:

46 chromosomes Diploid (2n).

how many chromosomes are in Sex cells (gametes)

Haploid (n).

what are Autosomes?

First 22 pairs of chromosomes.

what are Sex Chromosomes

23rd pair (XX = female, XY = male).

what are genes? (important)

Segments of DNA that code for proteins.

what are proteins

Molecules that perform various functions in the body.

what is the Purpose of Cell Division

Growth, repair, maintenance, reproduction.

what are the 3 Main Steps of DNA Replication (DNA → DNA)

Unwinding (DNA helicase separates strands).

Base pairing (A-T, C-G).

New strand formation (DNA polymerase builds new strands).

what does the cell do during interphase in mitosis?

DNA replicates in preparation for division.

Prophase in mitosis

Spindle fibers form, chromosomes condense, nuclear membrane disappears.

Metaphase in mitosis

Chromosomes align in the center (equator).

anaphase in mitosis

Sister chromatids separate and move to opposite sides.

telophase in mitosis

Two nuclei form within the cell.

Cytokenesis in mitosis

Cell divides into two genetically identical daughter cells.

animal cells during Cytokenesis

Cleavage furrow forms.

Plant cells druing cytokenesis

Cell plate forms.

Checkpoints in mitosis (their role)

Ensure proper cell division.

Cancer found in cells during mitosis

Uncontrolled cell division due to failed checkpoints.

Chromatin definition

The uncoiled form of DNA

Chromatid definition

Half of a duplicated chromosome.

Chromosome contains

Condensed DNA.

Centromere

Holds chromatids together.

Centrioles

the things that form the spindle fibres that pull the sister chromatids apart

Spindle fibers

Help separate chromosomes.

Diploid (2n)

full set of chromosomes

Haploid (n)

half the number of chromosomes

how many cells does meiosis produce? are they identical?

Produces 4 genetically unique gamete cells.

Prophase I in meiosis

crossing over

metaphase 1 in meiosis

Homologous pairs align at the center.

Anaphase I in meiosis

Homologous chromosomes separate.

Telophase I & Cytokinesis in meiosis

Two haploid cells form.

Prophase II in meiosis

Spindle fibers reform.

Metaphase II in meiosis

Chromosomes align at the center.

Anaphase II

Sister chromatids separate.

Telophase II & Cytokinesis in meiosis

Four genetically unique haploid cells form.

what do Spermatogenesis (male) produce?

Produces 4 sperm cells.

what do Oogenesis (female) produce?

Produces 1 egg + 3 polar bodies.

what is Independent Assortment?

Occurs in Metaphase I (random alignment of chromosomes).

what is Random Fertilization

Any sperm can fertilize any egg.

what happens in the first Trimester (0-12 weeks)

Major organs start forming.

Heart begins to beat.

what happens in the Second Trimester (13-26 weeks)

Skeleton forms.

Mother feels movement.

what happens in the Third Trimester (27-40 weeks)?

Rapid growth.

Lungs mature for birth.

exmaples of asexual reproduction

Binary Fission (Bacteria).

Budding (Yeast, Hydra).

Fragmentation (Starfish).

Vegetative Reproduction (Plants).

Artificial Cloning (Lab methods).