GBIO Final (Eva Hillmann; Southeastern Louisiana University)

Binary Fission

A form of asexual reproduction in single-celled organisms (in this case, bacteria) by which one cell divides into two cells of the same size

Steps of bacteria replication

1) starts at the bacteria
2) splits in two directions (opposite, typically)
3) Septum (cell wall) is formed, causing a termination of replication

Eukaryotic organisms have how many chromosomes...

10-50 chromosomes (chromatid pairs)

How many chromosomes do humans have?

46 (23 pairs)

Diploids

(2N) Humans; 46 chromosomes

Haploid

(N) Sperm/egg; 23 chromosomes

Homologue

a chromosome pair; each chromosome pair is alike in size and trait (eye color, hair color, etc)

Chromatin

mixture of DNA and proteins

Chromatin mixture ratio

DNA -- 40%
Protein -- 60%

Chromosome replication (beginning)

each chromosome has 1 DNA molecule

Chromosome replication (ending)

each chromosome has 2 identical DNA molecules (sister chromatids)

G1 (gap 1)

growth and development

what phase does DNA replication happen

G2 (gap 2)

preparation for division

M-phase (mitotic)

5 subphrases (PMAT-C)

Cytokinesis

division of the cytoplasm into 2 cells
(end of m-phase)

Centromeres

point of constriction

Kinetochore

point of attachment for microtubules

Steps of Interphase

1) G1
2) S
3) G2

Prophase

Chromosomes become visable, nuclear envelop dissolves, spindle forms

Prometaphase

The second stage of mitosis, where MICROTUBULES attach to the KINETOCHORES

Metaphase

Chromosomes line up in the middle of the cell

Anaphase

sister chromatids (DNA copies) are pulled apart to opposite sides of the cell

Telophase

Nuclear envelope reforms; cell starts to pinch

Cytokinesis

Cell splits in half
(Animal cells: furrow)
(Plant cells: cell plate/wall)

Meiosis

sexual life cycles

Diploid cells

A cell containing two sets of chromosomes (2n), one set inherited from each parent.

Haploid cells

gametes, containing a single set of 23 chromosomes

Meiosis features

-- 2 rounds of division

-- synapsis (homogonous pairing)

-- chiasmata (crossing over)

-- NO DNA REPLICATION (unlike mitosis)

Interphase process

G1
S
G2

Meiosis 1

PMAT-1
(prophase 1)
(metaphase 1)
(anaphase 1)
(telophase 1)

Meiosis 2

PMAT-2
(prophase 2)
(metaphase 2)
(anaphase 2)
(telophase 2)

Josef Kolreuter (1760)

crossed tobacco strains to produce hybrids that differed from both parents

T.A. Knight (1823)

-crossed 2 varieties of garden pea, Pisum sativa
~ crossed 2 true-breeding strains
~ 1st generation resembled only 1 parent strain
~ 2nd generation resembled both

Gregor Mendel

applied science to his work with pea plants

Mendel steps

1) produce true breeding strains for each trait
2) cross fertilize treu breeding plants to create alt. forms of a trait

Monohybrid crosses

study 2 variations of a single trait

P

parent generation

F1

first filial generation

F2

second filial generation

F1 generation (ratio)

1:1 (100%)

F2 generation (ratio)

3:1 (75% -- 25%)

Mendel discovered

1 dominant trait
1 recessive trait
(for each genetic trait)

Mendel's model

1) Trait variation is due to alternative versions (alleles) of heritable factors (genes)
2) For each character an organism inherits two alleles, one from each parent
3) Dominant alleles mask recessive alleles
4) Two alleles for a heritable character segregate (separate) during gamete formation and end up in different gametes (= Law of Segregation)

List of expressions

Dominant allele
Recessive allele
Phenotype
Genotype

Allele

alternative forms of a gene

Homozygous

2 of the same allele

Heterozygous

1 of each allele

Homorozygous Dominant

two same genes that are dominant; AA

Factors affecting phenotypes

1) environment
2) continuous variation (gradients, such as skin color or hair color)
3) Pleiotropy (diseases or disfigures that are almost impossible to predict)
4) Multiple alleles (blood type most commonly)
5) Co-dominance (mixture of 2 traits of the same gene that show together, such as light brown skin when mixed with white and brown)
6) Incomplete dominance (one trait is dominant over the other dominant trait)