Biology Meiosis and Mitosis

Somatic Cell

Any cell of an organism other than the reproductive cells

Turner’s Syndrome

Missing one X chromosome, only viable human monosomy, female and sterile

Down syndrome

trisomy 21, extra chromosome in 21

Klinefelters

XXY, male with feminine features

Gamete

sex cell; sperm or egg

Where are gametes found?

Ovaries or testes

Diploid number

The full number of chromosomes in a somatic cell

Haploid number

Half the normal number of chromosomes; found in sex cells

Homologous chromosomes

pair of chromosomes that are the same size, same appearance and same potential genes, one is from the mom and the other is from the dad

Sister chromatids

Replicated forms of a chromosome joined together by the centromere

When are sister chromatids shown?

During cell division

Zygote

The cell that is formed by the union of the sperm and egg. Half of the DNA is from the egg and the other half is from the sperm

Sperm

Carries DNA with only a nucleus, 23 chromosomes

Egg

Containing 23 chromosomes

Chromatin

Loosely packed DNA in your nuclei, exists before DNA is copied

Chromosome

Condensed DNA formed when the cell is preparing for cell division

Gene

Segment of DNA that codes for a protein, have a specific location on a given chromosome

Diploid number

2n

Haploid number

2

Karotype

A visual pairing of the chromosomes from largest to smallest, with the SEX chromosomes as the final pair

Centromere

Joins together replicates of individual chromosomes/sister chromatids

Mitosis

The process in which new SOMATIC cells divide after the DNA is replicated

Meiosis

The process in which new gametes are divided after the DNA is replicated

Order of interphase

G1, S, G2

G0 phase

exits from the cell cycle (non dividing cell)

G1 Phase

cell metabolically active, duplicates organelles and cytosolic components

G1 phase

centromere replication begins

S phase

DNA is replicated

G2 Phase

cell growth continues

G2 phase

centromere replication completed

Mitotic phase acronym

PMAT

Prophase

Replicated chromatin is beginning to condense into chromosomes, mitotic spindle is forming from centrosome

Mitotic spindle is made of…

Microtubules

Sister chromatids are attached to the mitotic spindle by a … in the centromere

Kinetochore

Metaphase

Sister chromatids are attached to a mitotic spindle (the phase not the name of the connector)

Metaphase

nuclear envelope is completely dissolved

Metaphase

mitotic spindle spans the entire cell

Metaphase

Chromosomes (sister chromatids) are lined up in the middle of the cell

Anaphase

Centromere dissolved allowing the sister chromatids to operate/seperate

anaphase

chromosomes begin to migrate the opposite sides of the cell

telophase

chromosomes are as far apart as possible

telophase

2 nuclear envelopes are forming

telophase

mitotic spindle is breaking down

telophase

cytokinesis is beginning

cytokinesis

follows mitosis

cytokinesis

division of the cell/ cytoplasm to create 2 new cells

cytokinesis in animal cells create a …

clevage furrow

cytokinesis in plant cells form a…

cell plate

centromere

made of centrioles

what are centrioles

the mitotic spindke grows from here

p53

The concentration of these signals that the cell is healthy, tumor supressor protein

p53 is found in…

G1

Cyclin D

Made by the cell and tells the cell to proceed to S phase

Cyclin D is made in

G1

CDK

makes sure that the DNA was replicated accurately without mistakes.

CDK is made in…

G2

Cyclin A

helps to move the cell through the G2 phase and makes sure DNA replication is complete

Cyclin A is made in…

G2

Apoptosis

The process by which the cell is deliberately killed, can occur due to infection, damage, improper function, or the cell not taking the proper cues through the cycle

Proginator cell

Somatic cell in lining of the testes or ovaries that creates sex cells

Prophase 1

Crossing over occurs, the nuclear envelope dissolving, chromatin condensing into chromosomes, meiotic spindle forming

Crossing over

Homologous chromosomes find each other and physically touch each other, swapping bits of genetic information.

Chasmal

Place where chromosomes cross over

Metaphase 1

Random assortment of chromosomes as they line up at the metaphase plate (middle of the cell)

Anaphase 1

homologous chromosomes begin to seperate (sister chromatids stay together)

Telophase 1

Chromosomes far apart as possible, nuclear envelopes forming, cytokinesis has begun

what is meiosis 1

The first stage of meiosis, meiosis I is where homologous chromosomes are separated into two daughter cells, reducing the chromosome number by half. This process includes prophase I, metaphase I, anaphase I, and telophase I.

what is meiosis 2

Meiosis II is the second division of the meiotic process in which sister chromatids are separated and ultimately result in four haploid cells from the original diploid cell.

what are the distinguishing features of meiosis 1 and meiosis 2

Meiosis 1 involves homologous chromosome separation and reduction of chromosome number by half, while Meiosis 2 resembles mitosis, focusing on the separation of sister chromatids.

what are two ways that genetic diversity is increased in meiosis 1

Genetic diversity in meiosis 1 is increased through crossing over and independent assortment. Crossing over occurs when homologous chromosomes exchange genetic material, while independent assortment allows different combinations of chromosomes to be inherited.

Understand that the incidence of down’s syndrome increases significantly with maternal age

as older mothers are more likely to have chromosomal abnormalities during meiosis, leading to an increased risk of having a child with Down syndrome.