Chapter 9 & 10 ~ The Cell Cyle & Meiosis And Sexual Life Cycles Flashcards by Sujad Syed

Cell division

The continuity of life is based on the reproduction of cells

Roles:
- division of one prokaryo cell reproduces an entire organism
- enables multicellular eukaryos to develop from a 1 cell
- cell division continues after growth (renewal and repair, replacing dead cells from tears)

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Asexual reproduction

Process:
- single parent organism
- parent cell undergoes mitosis to produce genetically identical offspring
- no exchange of genetic material btwn different individuals

Products:
- genetically identical individual
- clones of the parent
- genetic diversity is limited

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Sexual reproduction

Process:
- two parent organisms contributing genetic material
- specialized cells are produced (chromosome number is 1/2)
- fertilization occurs and combines genetic material

Products:
- genetically unique individuals
- inherit a combination of genetic material (genetic diversity)
- recombination

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Chromosomes

Long, thread like structure found in the nucleus and are composed of DNA and associated proteins.

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Chromatin

The entire complex of DNA and proteins that is the building material of chromosomes

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Chromosome Duplication

Interphase (chromosome duplication in S phase)
- after duplication, there are 2 sister chromatids connected along their lengths by sister chromatid cohesion

Mitotic phase (duplicated chromosomes are separated into daughter cells)

Cell division (chromatids are pulled to opposing ends)

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Interphase

G1 phase: cell growth, function, checking for DNA damage, decision for cell division

S phase: DNA replication, formation of sister chromatids, accuracy and fidelity, protein synthesis, completion of DNA replication

G2 phase: nuclear envelop encloses nucleus, two centrosomes are formed, chromosomes are not seen separated yet

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Prophase

Chromatin becomes more tightly coiled
Nucleoli disappears
Duplicated chromosomes appear as two sister chromatids
Mitotic spindle begins to form
Centrosomes move away from each other

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Prometaphase

Nuclear envelope breaks
Microtubules invade nuclear area
Chromosomes become more condensed

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Metaphase

Centrosomes are not at opposite poles of the cell
Chromosomes have arrived at the metaphase plate

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Anaphase

Shortest stage of mitosis
Two sister chromatids suddenly part becoming chromosomes
Chromosomes move toward opposite ends of the cell
The cell elongates
Two ends of the cells have a complete collection of chromosomes

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Telophase

2 daughter nuclei form in the cell
Nucleoli reappear
Chromosomes become less condensed
Spindle microtubules are depolymerized
Mitosis is complete

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Cytokinesis (animal cell)

Division of the cytoplasm
For action of cleavage furrows
Cell membrane pinching
Formation of 2 daughter cells

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Cytokinesis (plant cells)

Vesicle formation
Cell plate formation
Cell wall deposition
Formation of 2 daughter cells

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Cell cycle control system

Checkpoints
Cell Cycle phases
Cell signaling

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Cell cycle control system (consequences of errors)

Cancer
Genetic mutation
Cell death
Cellular dysfunction
Aging
Developmental abnormalities

How are cancer cells different from healthy cells?

uncontrolled growth
Loss of contact inhibition
Genetic mutations
Autonomy (evade signals from other cells)
Immortality
Invasion and metastasis
Resistance to apoptosis
Angiogenesis (induce formation of new blood vessels)
Heterogeneity

Benign tumors

non cancerous that do not invade nearby tissues and organs
Resemble normal cells
Do not metastasize
Not life threatening and can be surgically removed

Malignant tumors

Cancerous growths characterized by uncontrolled growth
Abnormal behavior (uncontrolled division, evade programmed death)
Ability to metastasize
Can be life threatening

“Slash, Burn, Poison”

Surgery (slash)
Radiation therapy (burn)
Chemotherapy (poison)

How to reduce the risks of developing cancer

Healthy diet
Regular physical activity
Tobacco avoidance
Sun protection
Limit alcohol consumption
Cancer screenings
Vaccinations
Healthy weight
Limit exposure to radiation
Breastfeeding

Sex chromosomes

Pair of chromosomes that determine an individual’s sex

2 sets in humans: X and Y (males: XY , females: XX)

Autosomes

All the chromosomes in an organism’s genome except for the sex chromosome

Somatic Cells

Non-reproductive cells that make up the tissues of the organs in the organism

Are diploid (2 sets of chromosomes, one from each parent)

Gametes

Reproductive cells involved in sexual reproduction Sperm and Egg Are haploid (1 set of chromosomes)

Diploid

2 sets of chromosomes, one from each parent Humans have a total of 46 chromosomes (23 pairs) Found in somatic cells

Haploid

One set of chromosomes 23 chromosomes (1/2 the ones in diploid) Sperm & Egg

Why the production of haploid gametes in sexually reproducing organisms is necessary

Combination of genetic material Genetic variation Recombination Purging harmful mutations Dilution of recessive traits Evolutionary advantage Species survival

Meiosis I (process)

Prophase I: chromosomes condense, homologous pair up, genetic recombination occurs through crossing over Metaphase I: homologous chromosomes line at the equator (1 chromosome from each parent) Anaphase I: homologous chromosomes are separated and pulled to opposite poles (ec gets 1 set of chromosomes) Telophase I: 2 haploid daughter cells are formed with a unique combination of chromosomes

Meiosis I (products)

2 genetically distinct (from crossing over) haploid daughter cells, each with 1/2 the number of chromosomes as original diploid

Meiosis II (process)

Prophase II: chromosomes condense again in the two haploid daughter cells from meiosis I Metaphase II: chromosomes align at the equator Anaphase II: sister chromatids are separated and pulled to opposite poles of the cell Telophase II: 4 genetically unique haploid daughter cells are produced

Meiosis II (product)

4 haploid daughter cells with 1/2 the number of chromosomes as original diploid cell. They are the final gametes in sexual reproduction

Genetic diversity in Meiosis

Maternal and paternal chromosomes can be distributed randomly into different gametes The number of possible combinations of chromosomes that can result from assortment is 2^n (n= haploid chromosomes) Offspring can inherit a wide variety of genetic combinations from their parents leading to genetic diversity

Genetic diversity in fertilization

In sexually reproducing organisms, there are many combinations of super and egg gametes due to meiosis The sperm when fertilizing the egg is by chance. Random fertilization combines genetic material from two parents in a unique way for each offspring, adding to genetic diversity

Genetic diversity in crossing over

Occurs during meiosis I and is the recombination of genes on the chromosomes the exchange of genetic material between chromatids of homologous chromosomes creates new combinations which contribute to genetic diversity

Nondisjunction

A chromosomal abnormality that occurs during meiosis when chromosomes fail to separate properly; can lead to incorrect number of chromosomes in gametes

Nondisjunction in autosomes

Trisomy: nondisjunction that results in the presence of an extra autosome in the zygote leads to trisomy (Down syndrome) which results from an extra copy of chromosome 21 Monosomy: loss of one autosome, leading to monosomy. Common example is Turner syndrome, caused from the loss of one X chromosome in females

Nondisjunction in sex chromosomes

Sex chromosome trisomy: can lead to conditions where there is an extra X and Y chromosome; Klinefelter syndrome occurs in males who have an extra X chromosome Sex chromosome monosomy: loss of a sex chromosome; can lead to turner syndrome