Bio Unit 9

Meiosis and other stuff

homologous chromosomes

Pair of chromosomes that are the same size, same appearance and same genes.

How homologous chromosomes are distributed differently in meiosis versus mitosis

Homologous chromosomes line up together, while in mitosis they line up on their own spindle fiber. Law of independent assortment happens in meiosis at this point

Tetrad

Each pair of homologous chromosomes.

Crossing over occurs

Prophase 1

prophase 1

Chromosomes become visible; nuclear envelope breaks down; crossing-over occurs.

Metaphase 1

Paired homologous chromosomes line up across the center of the cell

anaphase 1

Homologous chromosomes separate

telophase 1

Homologous chromosomes continue to be pulled toward the centrioles. redcution division, start to separate cell

Meiosis Cytokinesis

split

meiosis 1

2 haploid cells

difference between prophase 1 and 2

tetrads don't form in prophase 2

metaphase 2

Chromosomes line up in the middle

anaphase 2

sister chromatids separate and move to opposite poles

telophase 2

A nuclear membrane forms around the chromosomes in each of the 4 haploid gametes being formed. Also chromosomes uncoil to form chromatin

Meiosis vs. Mitosis

- meiosis has 2 cell divisions, mitosis only one

- in meiosis homologous chromosomes pair up on cell's equator, in mitosis homologous chromosomes never pair up

- in anaphase 1 of meiosis sister chromatids are still paired, in anaphase in mitosis, sister chromatids are separated

- meiosis results in a haploid cell, mitosis results in a diploid

what happens after telophase 2 and cytokinesis

4 haploid gametes

haploid gametes

sperm and egg

haploid

1/2 set of chromosomes

diploid

full set of chromosomes

somatic cells

body cells

gamete cells

reproductive cells

Goals of meiosis

Reduce chromosomes by ½ and to have genetic variation

What causes genetic variation?

mutations and sexual reproduction and crossing over

how are chromosomes reduced by half in meiosis

reduction division

More about reduce \# chromosomes by 1/2

meiosis 1, b/c [homologous pairs separate]-law of segregation during anaphase 1

law of independent assortment

the law that states that genes separate independently of one another in meiosis

Law of Segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

More about create genetic diversity

a. during synapsis--\> crossing over b/w homologous chrom. can occur

b. law of independent assortment

a and b is meiosis

c. random fertilization

Fragmentation

type of asexual reproduction when a parent organism breaks into fragments, or pieces, and each piece develops into a new organism.

Types of asexual reproduction

binary fission, budding, fragmentation

budding

type of asexual reproduction in which an offspring cell pinches off from the parent cell

binary fission

method of asexual reproduction that occurs in prokaryotic cells in which a parent cell divides into two identical daughter cells.

asexual reproduction

Process by which a single parent reproduces by itself, which is genetically identical

Fertilization

union of two gametes that produces a diploid zygote

zygote

diploid cell that forms when two haploid gametes unite during fertilization

Is a zygote haploid or diploid?

diploid

How many chromosomes do humans have?

46

Assuming the body cell has 6 chromosomes. Draw what metaphase should look like if the cells would have 6 chromosomes at the end of the division. (Hint: What division should occur, Mitosis or Meiosis)

Somatic cells. Starting diploid to diploid, mitosis, each chromosome gets own spindle fiber.

chromosomal segment

section of dna on the chromosome

What are chromosomal mutations?

deletion, duplication, inversion, translocation, nondisjunction

Deletion

removes a chromosomal segment

synapsis

the pairing (process) of homologous chromosomes during prophase I of meiosis

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Nondisjunction

An error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other.

n+1

extra chromosome

n-1

not extra chromosome

chromosome mutations

Duplication

Deletion

Inversion

Translocation

Nondisjunction

duplication

change to a chromosome in which part of the chromosome is repeated

inversion

inverted segment of chromosomes

Translocation

Change to a chromosome in which a fragment of one chromosome attaches to a nonhomologous chromosome.

when do they chromosomal mutation happen?

prophase 1

Monosomy

Chromosomal abnormality consisting of the absence of one chromosome from the normal diploid number

Trisomy

a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities.

another name for crossing over

recombination

reduction division

another name for meiosis I, the division where homologous pairs separate.

Gametogenesis

the process in which cells undergo meiosis to form gametes.

cloning

A process in which a cell, cell product, or organism is copied from an original source.

stem cell

unspecialized cell that can give rise to one or more types of specialized cells

embryo

the developing human organism from about 2 weeks after fertilization through the second month

potent

power

order of the potents

totipotent, pluripotent, multi-potent

abbreviation of potents

TPM

totipotent

Stem cells with the potential to differentiate into any type of cell.

Pluripotent

Cells that are capable of developing into most, but not all, of the body's cell types

multipotent

cell with limited potential to develop into many types of differentiated cells

stem cells are \____ potent

pluri

Adult stem cells are

multipotent

induced pluripotent stem cells (iPS)

adult differentiated cell coaxed back to pluripotent cell

goal for stem cell use

supply cells for repair of damaged or diseased organs

bone marrow transplant

infusion of healthy bone marrow cells to a recipient with matching cells from a donor

independent assortment

process in which homologous chromosomes are randomly distributed to daughter cells, and different chromosomes segregate independently of each other.

Recombination

Exchange of genetic material between homologous chromosomes; occurs during prophase I; also known as crossing-over.

independent orientation

Random arrangement of homologous chromosomes during metaphase I, leading to genetic variation

random fertilization

the combination of each unique sperm with each unique egg increases genetic variability

Down Syndrome

a condition of intellectual disability and associated physical disorders caused by an extra copy of chromosome 21.

Klienfelter syndrome

genetic disorder characterized by a male with an extra X chromosome (XXY)

Turner's syndrome

Born with a single X chromosome. (short, webbed neck, different physical sexual development.)

Transgenic Therapy

Insertion of functional genes into cells in order to treat a disease

Goal of sexual reproduction and asexual reproduction

S. produce genetically different offspring

A. produce genetically identical offspring

how many processes are involved in a/sexual reproduction

S. 2 in Euk, meiosis and fertilization

A. 1

Amount of parent cells for meiosis vs fertilization

m. 1 (sperm and egg)

f. 2

\# of offspring from meiosis

4

\# of offspring for fertilization

1 (could be twins though)

\# of chromosomes from meiosis

haploid (1n)

\# of chromosomes from fertilization

diploid (2n)

Type of cell for meiosis

gamate, sex cells (sperm and egg), germ cell

Type of cell for fertilization

zygote/ fertilized egg