Cellular Reproduction: Mitosis and Meiosis Overview

Why do unicellular organisms cells divide?

In order to reproduce

Why do multicellular organisms cells divide?

To grow and develop and repair and replace damaged cells

Describe the process of binary fission

Prokaryotes divide through binary fission.

How many chromosomes are present in a prokaryote?

One chromosome

Are the daughter cells produced in binary fission identical to the parent cell or different?

Identical

Define: genome

The complete set of genetic code for an organism.

Define: chromatin

Relaxed DNA inside a non-dividing cell.

Define: chromosome

Supercoiled DNA inside a dividing cell.

Define: karyotype

To view the chromosomes of a cell.

Define: homologous chromosome

Pairs of chromosomes with the same genes in the same places.

Define: alleles

Different versions of the same genes.

What do DNA nucleosomes resemble?

Beads on a string.

What are the proteins that DNA molecules are coiled around?

Histones.

Does every cell in your body have the same DNA inside?

Yes.

How many chromosomes are in a human cell?

46 chromosomes.

What do karyotypes help you check for?

Missing chromosomes.

What do karyotypes let you check for?

Chromosomal abnormalities.

What are autosomes?

If chromosomes are in pairs numbered 1-22 they are autosomes.

What are sex chromosomes?

If chromosomes have a letter X or Y they are sex chromosomes.

How many pairs of autosomes are in a normal human cell?

22 pairs.

How many pairs of sex chromosomes are in a normal human cell?

1 pair.

If you have XX sex chromosomes, your gender is?

Female.

If you have XY sex chromosomes, your gender is?

Male.

What happens in G1 phase?

This is where you are duplicating all your organelles, the cell is growing larger.

What happens in S-phase?

Copying your DNA.

What happens in G2 phase?

Double check to make sure all the copying went well and making some proteins that you need to do for mitosis.

What does G stand for in G1, G2?

Growth.

What does S stand for in S-phase?

Synthesis.

When DNA copies, what are the two identical chromosomes called?

Sister chromatids.

What structure links sister chromatids?

Centromere.

Where do spindle fibers attach during mitosis?

Kinetochores.

Where do spindle fibers grow from?

Centrioles which are anchored at the centrosomes.

How many sister chromatids are present after the S-phase of mitosis if we start with 46 chromosomes?

92

If a non-human cell has 16 chromosomes after the S-phase of mitosis, how many were there originally?

16

What happens during prophase?

Nuclear membrane breaks down and spindle fibers form and attach to kinetochores.

What happens during metaphase?

Sister chromatids line up in the middle of the cell.

What happens during anaphase?

Sister chromatids are pulled to the opposite sides of the cell.

What happens during telophase?

Nuclear membrane begins to reform and chromosomes begin to uncoil.

What is cytokinesis?

In cytokinesis, the two daughter cells physically separate.

How does cytokinesis differ in plant and animal cells?

Cytokinesis in plant cells forms a cell plate, while in animal cells, the membrane pinches in.

Cytokinesis

The process where the two daughter cells physically separate.

Division furrow

A structure that forms in animal cells during cytokinesis.

Cell plate

A structure that forms in plant cells during cytokinesis.

G1 checkpoint

Checks the DNA before it is copied and nutrient availability.

G2 checkpoint

Checks if the DNA has finished replicating and if the DNA copy is correct.

M checkpoint

Checks if the chromosomes are properly attached to the spindle fibers.

G0 phase

A resting state where cells are not actively dividing.

Triggers for G0

A cell goes into G0 if it is starving or doesn't have enough nutrients.

Human cells in G0

Neurons, skeletal muscle cells, and cardiac muscle cells.

Telomeres

Protective caps on the end of chromosomes.

Telomere shortening

Telomeres shorten each time a cell divides.

Damaged DNA and cell cycle

Cells with damaged DNA will not be allowed to complete the cell cycle.

Cancer cells and division

Cancer cells can keep dividing indefinitely due to the enzyme telomerase.

Telomerase function

Repairs telomeres.

Tumor

Extra cells that form a ball.

Benign tumor

Extra cells that are harmless and don't spread.

Malignant tumor

Tumor cells that are dangerous and will spread to other organs and tissues.

Gamete

A reproductive cell.

Male gamete

Sperm.

Gamete production in males

Gametes are made in the testes.

Female gamete

Egg.

Gamete production in females

Gametes are made in the ovaries.

Meiosis

The process that forms gametes.

Fertilization

Where the egg meets the sperm and the genetic information fuses together.

Zygote

The first cell of the new organism.

Haploid

Having only one copy of each chromosome.

Diploid

Having two copies of each chromosome; homologous pair.

Meiosis results

The results of meiosis are 4 different haploid cells.

Mitosis usage

Used after fertilization for growth and repair.

Haploid and diploid cells in life cycle

Gametes are haploid and zygotes are diploid.

Chromosome numbers

If a haploid gamete has 8 chromosomes, the diploid cell has 16 chromosomes; if a 2n cell has 46 chromosomes, the haploid cell has 23 chromosomes.

Homologous chromosome

Chromosomes that contain genes for the same traits but aren't identical.

Allele

Alternative forms of a gene.

Sister chromatids

Copies of each other; they contain exactly the same genetic information.

DNA copying in meiosis

DNA is copied during the S phase.

Crossing over

Takes place during prophase 1.

Homologous chromosomes separation

Occurs during meiosis 1.

Sister chromatids separation

Occurs during meiosis 2.

Prophase 1

Homologous chromosomes line up in pairs; chromosomes may swap homologous pieces of DNA.

Metaphase 1

Chromosomes line up in the middle of the cell.

Anaphase 1

Homologous chromosomes are pulled to opposite poles.

Telophase 1

Homologous chromosomes are pulled to opposite poles.

Prophase 2

Centromere breaks.

Metaphase 2

Chromosomes line up along the equator of the cell.

Anaphase 2

The sister chromatids break apart and are pulled to opposite poles.

Telophase 2

Nuclear membrane is reformed and start to pinch in the plasma membrane.

Spermatogenesis

Produces 4 functional sperm.

Oogenesis

Produces 1 functional egg and 3 polar bodies.

Chiasma

The site of crossing over.

Independent assortment

The random alignment of chromosomes at metaphase 1 contributes to genetic variation.

Random fertilization

The process by which any sperm can fertilize any egg, contributing to genetic variation.

Monosomy

A condition where there is a missing chromosome.

Trisomy

A condition where there is an extra chromosome.

Non-disjunction in meiosis 1

Homologous chromosomes fail to separate.

Non-disjunction in meiosis 2

Sister chromatids fail to separate.

Down syndrome

A trisomy of chromosome 21.

Edward syndrome

A trisomy of chromosome 18.

Turner syndrome

A monosomy condition resulting in a female phenotype; the person is not fertile.

Klinefelter syndrome

A trisomy condition resulting in a male phenotype; the person is not fertile.

Jacob syndrome

A trisomy condition resulting in a male phenotype; the person is fertile.