Gen-Bio 2nd Qrt (Yawa kau)

Kendz's note: Watch vids from yt abt parts of mitosis and just read L09 about the Disorder and Diseases if u wanna learn more about the diseases (diko na sinali ung in-depth description nila :))*Tinatamad nako*

The cell cycle

is the process by which cells grow, Replicate their DNA, and divide.

Stages of DNA and Cell Replication

G1 phase, S phase, G2 phase, M phase

G1 phase

when the cell prepares for division with metabolic changes.

S phase

when the DNA and genetic material of the cell are duplicated, forming two sister chromatids.

G2 phase

when cytoplasmic materials needed for division are gathered with metabolic changes.

M phase

when the genetic material and the cell divide.

S phase

The actual DNA replication occurs during _____ , when two copies of the original cell DNA are produced, each containing one original and one new strand of DNA

G1 phase

S Phase

S Phase

DNA Synthesis

G2 Phase

M Phase

Cytokinesis

Variations in Cell Cycle Duration

Control Mechanisms of the Cell Cycle

Cancer

group of diseases characterized by uncontrolled cell growth

Mutations

can occur due to replication errors or environmental factors

Interphase

Mitotic Phase

Mitosis (M phase)

is the part of the cell cycle in which a cell divides into two identical daughter cells, which are genetically identical to each other as well as the "mother" cell.

Importance of the Cell Cycle

The Cell Cycle

is an ordered series of events involving cell growth and cell division that produces two new daughter cells. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and nuclear and cytoplasmic division that ultimately produces two identical (clone) cells.

Interphase and the Mitotic phase

The cell cycle has two major phases

Interphase

During ______, the cell grows and the nuclear DNA is duplicated.

Mitotic phase

During the ______, the duplicated chromosomes are segregated and distributed into daughter nuclei.

Two genetically identical daughter cells

Following mitosis, the cytoplasm is usually divided as well by cytokinesis, resulting in .

G1 phase

During this phase, a cell grows rapidly and carries out its routine functions. It occupies the major portion of the cell’s life for mostly organisms. In this phase, the cell that are not divided will remain. Most muscle and nerve cells, never divide and if these cells die, the body cannot replace them.

S phase

During this phase, a cell’s DNA is copied. At the end of this phase each chromosome has two chromatids at the centromere

G2 phase

This is the preparation for the nucleus to divide. The microtubules is a hollow protein fibers that are rearranged during _____ for preparation for mitosis.

Mitosis

Is a multistep process during which the duplicated chromosomes are aligned, separated, and move into two new, identical daughter cells

Cytokinesis

is sometimes viewed as the second main stage of the mitotic phase, during which cell division is completed via the physical separation of the cytoplasmic components into two daughter cells.

Prophase

Prometaphase

Metaphase

Anaphase

Telophase

Cytokinesis

Cancer

comprises many different diseases caused by a common mechanism: uncontrolled cell growth.

Meiosis

Sexually reproducing species create their sperm, eggs, and sex cells through a process called _____

Germ Cell

A specialized cell called a _______divides during meiosis to create four new sex cells, each of which has half as many chromosomes as the original ______

Gametes

are created during meiosis, which is necessary for sexual reproduction.

True

The number of chromosomes is reduced from two sets to one set during meiosis.

False

The number of chromosomes is reduced from two sets to one set during mitosis.

Mitosis

guarantees that the quantity of the parent cell's chromosomes are identical to those of its two daughter cells.

Mitosis

_____ generates new cells and replaces injured, destroyed, or aging ones. Skin cells, blood cells, bone cells, connective tissues, structural cells in plants, and fungi are a few examples of body cells that go through _____

Inherited Disorders

can arise when chromosomes behave abnormally during meiosis.

abnormalities in chromosome number and chromosome structural rearrangements

Chromosome disorders can be divided into two categories

Abnormalities in Chromosome Number

These occur when there is an incorrect number of chromosomes in a cell.

Abnormalities in Chromosome Number

Ex:

a. trisomies (such as Down syndrome, where there is an extra copy of chromosome 21) b. monosomies (such as Turner syndrome, where one X chromosome is missing)

Abnormalities in Chromosome Number

These abnormalities arise from nondisjunction, the failure of chromosomes to separate properly during meiosis.

Chromosome Structural Rearrangements

These occur when chromosome segments are altered through duplications, deletions, inversions, or translocations. _______ changes can disrupt multiple genes within affected segments, leading to significant health problems.

Chromosome Structural Rearrangements

Ex:

a deletion of part of chromosome 5 causes Cri du Chat syndrome, which affects development and intellectual abilities.

Karyotype

is the number and appearance of chromosomes, including their length, banding pattern, and centromere position.

Karyogram

To obtain a view of an individual’s karyotype, cytologists photograph the chromosomes and then cut and paste each chromosome into a _______

Cytogenetics

is the study of chromosome structure and number, is essential for detecting chromosomal abnormalities that lead to genetic disorders.

Karyotype

represents the full set of an individual’s chromosomes, organized by

a. number,

b. length,

c. banding patterns,

and d. centromere positions.

Nondisjunctions, Duplications, and Deletions

Of all the chromosomal disorders, abnormalities in chromosome number are the most easily identifiable from a karyogram. Disorders of chromosome number include the duplication or loss of entire chromosomes, as well as changes in the number of complete sets of chromosomes.

Nondisjunction

They are caused by _______, which occurs when pairs of homologous chromosomes or sister chromatids fail to separate during meiosis.

Nondisjunction

occurs when chromosomes fail to separate properly during meiosis (in the formation of gametes) or mitosis.

Nondisjunction

Process: During meiosis, chromosomes are supposed to split so that each gamete receives only one chromosome from each pair. When ________happens, both chromosomes go to one gamete, while the other receives none.

Results: This can lead to aneuploidy, a condition in which cells have an abnormal number of chromosomes.

Down Syndrome

Caused by an extra copy of chromosome 21 (trisomy 21).

Turner Syndrome

Occurs when an individual has only one X chromosome (45, X).

Klinefelter Syndrome

Occurs in males with an extra X chromosome (47, XXY)

Duplication

occurs when a section of a chromosome is copied, resulting in multiple copies of that segment within the chromosome.

Duplication

Process: _______can occur due to errors during DNA replication or as a result of unequal crossing-over during meiosis, where homologous chromosomes exchange unequal lengths of DNA.

Results: This can lead to genetic imbalances, where too much of certain proteins or enzymes are produced, potentially affecting development and cellular functions.

Charcot-Marie-Tooth Disease Type 1A

Caused by a duplication on chromosome 17, affecting peripheral nerve function.

Pallister-Killian Syndrome

A rare disorder that results from the duplication of material from chromosome 12 and causes developmental and intellectual disabilities

Deletion

occurs when a segment of a chromosome is missing or deleted.

Deletion

Process: ______can occur through errors in DNA replication, exposure to harmful environmental agents (e.g., radiation), or incorrect chromosome separation.

Results: ______ can lead to a loss of important genes, resulting in various developmental abnormalities or diseases, depending on the size and location of the deleted segment.

Cri du Chat Syndrome

Caused by a deletion on the short arm of chromosome 5, leading to intellectual disability and distinctive facial features.

Williams Syndrome

Caused by a deletion of approximately 26-28 genes on chromosome 7, affecting physical and cognitive development.

chromosome inversion

is the detachment, 180° rotation, and reinsertion of part of a chromosome.

Duplication

• Extra copies of chromosome segments

• Can lead to overexpression of genes

Deletion

• Loss of chromosome segments

• May result in loss of important genetic information

Inversion

• Chromosome segment is flipped 180 degrees

• Can disrupt gene function or regulation

Mitosis

is the process of cell division that creates diploid cells. It plays a vital role in cell growth and repairing damaged tissue. Mitosis is divided into four main stages:

  Prophase

  Metaphase

  Anaphase

  Telophase

Karyokinesis

another term for Mitosis

Diploid Cells

These cells have two sets of chromosomes, one from each parent. In humans, _____ cells have 46 chromosomes arranged in 23 pairs. _____cells make up most of the body's tissues and are involved in growth and repair. They divide through a process called mitosis.

Haploid cells

These cells have only one set of chromosomes. In humans,________ cells contain 23 chromosomes. _________are the reproductive cells (sperm and eggs) and are involved in sexual reproduction. They are produced through a process called meiosis.

Diploid

Two sets of chromosomes (46 total in humans); found in body cells.

Haploid

One set of chromosomes (23 total in humans); found in gametes (sperm and eggs).

Diploid

Haploid

Prophase

is the first phase of mitosis.

-The nuclear envelope breaks down, and organelles like the Golgi and ER disperse.

-The nucleolus disappears, and centrosomes move to opposite poles of the cell.

-Microtubules form the mitotic spindle, pushing the centrosomes apart.

-The sister chromatids coil tightly and become visible under a microscope.

Prometaphase

the nuclear envelope breaks down further, and the mitotic spindle grows.

-Chromosomes condense more, and each sister chromatid forms a kinetochore that attaches to spindle microtubules.

-These microtubules align the chromosomes, pulling them towards opposite poles.

-Polar microtubules help elongate the cell, while astral microtubules assist in spindle orientation.

Metaphase

all chromosomes line up in the middle of the cell, forming the metaphase plate.

-The sister chromatids remain attached by cohesin proteins, and the chromosomes are fully condensed.

Anaphase

cohesin proteins break down, and sister chromatids separate.

Each chromatid, now a chromosome, is pulled toward opposite poles.

The cell elongates as polar microtubules slide against each other.

Prometaphase

Anaphase

Telophase

During this phase, the chromosomes move to opposite ends of the cell and start to unwind, transforming back into a relaxed form called chromatin.

The structures that helped separate the chromosomes, known as mitotic spindles, break down into smaller units called tubulin monomers.

These units will be reused to build the cytoskeleton for each new daughter cell.

New nuclear envelopes form around the chromosomes, and nucleosomes(the basic units of DNA packaging) begin to appear in the newly formed nuclei.

Meiosis

During this phase, the chromosomes move to opposite ends of the cell and start to unwind, transforming back into a relaxed form called chromatin.

The structures that helped separate the chromosomes, known as mitotic spindles, break down into smaller units called tubulin monomers. These units will be reused to build the cytoskeleton for each new daughter cell. New nuclear envelopes form around the chromosomes, and nucleosomes(the basic units of DNA packaging) begin to appear in the newly formed nuclei. Early in this stage, the chromosomes become clearly visible under a microscope. As the nuclear envelope starts to break down, proteins help bring homologous chromosomes (the same type of chromosome from each parent) close together. This close pairing is called synapsis. During synapsis, the genes on the chromatids of these paired chromosomes align perfectly with each other. It's important to note that synapsis does not happen during mitosis.

Synapsis

the genes on the chromatids of these paired chromosomes align perfectly with each other. It's important to note that _______ does not happen during mitosis.

Leptotene

The chromosomes start to condense and become visible

Zygotene

The chromosomes begin to pair up. These pairs are called homologous chromosomes. When they are paired together, they form structures known as tetrads, which consist of four chromatids.

Pachytene

This is the stage where crossing over occurs. During crossing over, sections of DNA are exchanged between homologous chromosomes. For example, if one sister chromatid has a gene for eye color labeled (A) and the other has (a) or (B) and (b), they may swap segments. This exchange point is called a chiasma. After crossing over, the sister chromatids may no longer be identical.

Diplotene

The chromosomes start to uncoil, becoming less tightly packed.

Diakinesis

The homologous chromosomes continue to separate further in preparation for the next stages of meiosis.

Five Substages of Prophase I:

Metaphase I