General Biology Exam 2

Genome

A cell’s total genetic material

Prokaryote

usually 1 circular DNA molecule

Eukaryotes

usually > 1 linear DNA molecules

Chromosomes

Molecule of DNA in a cell

Chromatin

DNA / protein complex in dispersed state thread- or fiber-like, DNA in this state when cell not actively dividing

Chromosomes (different definition)

“colored body”, DNA wrapped around proteins, Highly organized- high density, Only present during cell division

Haploid

(n), Having one complete set of chromosomes, Haploid cells have 1 of each chromosomes

Diploid

(2n), Having 2 complete sets of chromosomes, 2 of same chromosomes: homologous chromosomes or a homologous pair, same length, centromere location, genes

What cells are presented in humans they are diploid

Somatic cells

Haploid Example

n=2, gametes (male or female germ cells)

Diploid Example

2n=4, blood cells, skin cells, and muscle cells, somatic cells

Prokaryotes (Cell Cycle), How do they divide?

Binary Fission

Interphase

Time between cell divisions, Not a resting stage- cell highly active, Growth, synthesis, metabolic activity, Long- at least 90% of cell cycle, DNA is chromatin

What are the 3 phases of Interphase?

G1 (Gap 1), S Phase, G2 (Gap 2)

G1 (Gap 1)

Growth and normal development and functions, Preparation for S phase, Many cells spend most of there lives in G1

S Phase

S = Synthesis, Chromosomes duplicated- DNA and chromosomal protein synthesis-Does not change ploidly

What part are both of the sister chromatids are connected to?

Centromere

What part of the 2 sisters chromatids are located?

Telomere

What do 2 sister chromatids have in common?

Identical Copies

Is DNA is still presented in the chromatin during the S phase?

Yes

G2 (Gap 2)

Usually shorter than G1 or S Phase, DNA still as chromatin, High metabolic activities, preparations for mitosis

M Phase

Mitosis and cytokinesis, Shortest part of the cell cycle (<10%)

Mitosis

Nuclear division of somatic cells, Continuous process, Divided in 4 stages: Prophase, Metaphase, Anaphase, Telophase

What are the 4 stages of Mitosis?

1. Prophase, 2.Metaphase, 3.Anaphase, 4.Telophase

Prophase

3 big things happen":

Chromosomes condense

Nucleus breaks down

Mitotic spindle forms

Mitonic Spindle

Fibers within cell oriented from pole to pole of cell, Guide chromosomes movement during mitosis

Metaphase

Chromosomes align at metaphase plated

Anaphase

Sister chromotids sperate, move to opposite poles, Pulled by Kinetochores, After seperation, each chromatid considered to be a chromosomes

Kinetochores

proteins attached to centromeres

Telophase

Opposite of prophase, chromosomes start to de-condense, Nuclear envelope reforms, New nuclei identical to parent nucleus-that’s the point!

What phase is this?

Prophase

What phase is this?

Metaphase

What phase is this?

Anaphase

What phase is this?

Telophase

What is the number of daughter cells being produced after mitosis? (2n=4)

two daughter cells with 2n=4 in each

What is the number of daughter cells being produced after meiosis? (2n=4)

four daughter cells with n=2 in each

Cytokinesis

Part of M phase, Cytoplasmic divison —> 2 cells, each with 1 nucleus, Distinct process from mitosis, but generally overlaps with telophase

Cleavage Furrow

Contacts until parent cell pitched into two, Part of cytokinesis for “animal” cells

Cell Plate

new membrane at location of metaphase plate, fuses with plasma membrane, divides daughter cells, part of cytokinesis for “plant” cells

How many sister chromatids are in G1? (2n=4)

0

How many chromosomes are in G1? (2n=4)

4

How many chromosomes are presented in S phase?

8

How many homologous pair are presented in S phase?

2

How many sister chromatids are in S phase?

8

What phase is this?

G1 (Gap 1)

What phase is this?

S Phase

What phase is this?

G2 (Gap 2)

Heredity

Transmission of traits from one generation to the next (inheritance)

Variation

Differences between individuals

Genetics

The study of heredity and hereditary variation

Gametes

Reproductive cells that transmit genes from one generation to the next.

What can reproduction be?

Asexual and Sexual

Asexual Reporduction

Single parent produces offspring, Unicellular-split, Multicellular-budding or fragmentation

Where does Asexual reproduce?

Eukaryotes

Is Asexual a mitotic divison?

Yes

Asexual: How many offspring can 1 diploid (2n) parent produced?

2 diploid offspring

Asexual: How many offspring can 1 haploid (n) parent produced?

2 haploid offspring

Clones

offspring genetically identical to parent

Advantages of Asexual Reproduction

Fast, Low E required, Safe, Lots of offspring, Well adapted?, Don’t change

Sexual Reproduction

Fusin of 2 gametes to form a zygote

What does gamete (n) + gamete (n) equal to?

Fertilization—> zygote (2n)

Sexual: Are offspring genetically identical to their parents?

No

Are gametes usually from different parents?

Yes (but not always)

Costs of Sexual Reproduction

Slow, High E requirement, Dangerous-predation, decease often fewer offspring, Well adapted? Offspring only get half of your genes-genome dilution

Advantages of Sexual Reproduction

Genetic variation, Offspring represent novel combinations of parents’ genes, More likely able to survive environmental change of stress

What’s the problem about sexual reproduction?

If gametes have the same number of chromosome as parents --> chromosome number doubles when they fuse

What is the solution to this problem about chromosomes number double?

Meiosis

Meiosis

Reduction division, Cell divides twice

How many cells are produced when 1 diploid (2n) cell is split in meiosis?

2 haploid (n) cells

What are the 4 stages involve in Meiosis (including 2 cell divisions)?

1. interphase

2. Meiosis I

3. Interkinesis

4. Meiosis II

Interphase

Like before mitosis, chromosomes duplicate, Each chromosomes now 2 sisters chromatids (still chromatin)

How many chromatids are in humans (2n=46) during the interphase?

92

Meiosis I

First meiotic division-homologous chromosome separate, ploidy reduced, First and second meiotic divisions are indicated in the name of each stage: 

Prophase I, Metaphase I, Anaphase I, Telophase I

Prophase II, Metaphase II, Anaphase II, Telophase II

Prophase I

The same 3 prophase things as mitosis, plus new thing, Synapus, Genes in chromosomes align,

Synapus

Homologous chromosomes pair up

What does Prophase I result in?

Tetrad

Tetrad

2 homologous chromosome (4 chromatids) held together by proteins

Chromosomes Term

sister chromatids, duplicated chromosome (2 sister chromatids), Homologous pair (as a tetrad)

What’s the point of synapsis?

Crossing over (Homologues Recombination)

Crossing over (Homologues Recombination)

Exchages between non-sister chromatids in tetrad, Results in new combinations of genes, Important source of genetic diversity

At the End of Prophase I in Humans? (2n=46)

46 chromosomes, 23 tetrads, 92 chromatids

Metaphase I

Tetrads align at metaphase plate, Homologous chromosomes orient towards opposite poles

Anaphase I

Disjunction: Homologous chromosomes separate, Sister chromatids still connected, Chromosomes acted independently, Direction depends on orientation of tetrad.

Telophase I and Cytokinesis

Chromosomes may decondense, Nuclear envelope may reform, Cytokinesis occurs, results in 2 haploid cells, with duplicated chromosomes (sister chromatids still together)

At the end of Telophase in Humans ? (2n=46)

23 chromosomes in each cell, 46 chromatids, 0 tetrad

Interkinesis

Time between 1st and 2nd meiotic divisions, Usually short, interphase-like stage, No S phase, no DNA replication occurs

Meiosis II

2nd meiotic division, Chromatids separate into daughter cells, Very similar to mitosis (it’s basically just mitosis)

Stages of Meiosis II (separate sister)

Prophase II, Metaphase II, Anaphase II, Telophase II

At End of Telophase II in Humans? (2n=46)

23 Chromosomes in each cell, 0 tetrad, 0 chromatids

Which cell division involves in 2n cells?

Mitosis and Meiosis

Which cell division involves in n cells?

Mitosis

Number of Divisions in Mitosis

1

Number of Divisions in Meiosis

2

Delta chromosomes number in Mitosis

none

Delta chromosomes number in Meiosis

reduced by 1/2

What separates in anaphase in Mitosis?

sister chromatids

What separates in anaphase in Meiosis?

Homologous, then sister chromatids

Are there identical daughter cells in Mitosis?

Yes

Are there identical daughter cells in Meiosis?

No

Homologous Pairing in Mitosis?

No