BIOL 100 exam 2 - CH 19

DNA and specialized proteins, primarily histones

composed of chromatin

part of the DNA that directs synthesis of a specific protein

determines the trait (i.e. eye color)

all body cells except for gametes (egg and sperm).

a pair of chromosomes that bear genes for the same traits.

one member of each pair came from each parent

they are the same size, shape, and line up with one another during meiosis I

the condition of having two sets of chromosomes in each cell

i.e. somatic (body) cells

the pair of chromosomes involved in determining gender - x and y

the 22 pairs of chromosomes (excluding the sex chromosomes) that determine the expression of most of the inherited characteristics of a person

cell division of somatic cells

usually divided into prophase, metaphase, anaphase, and telophase

the entire sequence of events that a cell goes through from its origin in the division of a parent cell through is own division into 2 daughter cells

consists of 2 major phases: interphase and cell division

period of cell growth

3 stages:

• G1 (GAP 1)
• - - - metabolically active
• S (synthesis)
• - - - DNA is replicated
• G2 ( GAP 2)
• - - - organize & prep for cell division
• - - - make proteins to prep for mitosis

In mitosis:

- synthesis of water

- DNA is replicated

In mitosis:

- Growth of cell

- metabolically active

in Mitosis:

• - organize and prep for division
• - centrioles replicate
• - make proteins to prep for cell division

attachment point for spindle fibres

the region of a replicated chromosome at which sister chromatids are held together until they separate during cell division

one of the 2 identical replicates of a duplicated chromosome

• - unwound thread of DNA
• - Protein
• - - - histones used to package DNA

packaged into nucleosome

in mitosis, the phase when:

• - chromosomes condense
• - nuclear envelope disintigrates
• - centrioles migrate to opposite poles
• - spindle fibres attach to centrioles

phase of Meiosis

• - Chromosomes line up along the equator w/ homologue
• - - they line up in pairs (matched sets) 2x2

- microtubules attach to centromere of homologous chromosome

phase where chromosomes line up along equator

in mitosis, the shortest phase and when:

• - centromeres split
• - sister chromatids split
• - spindle fibers pull chromosomes to poles

in Meiosis

• - Homologous chromosomes separate
• - - (matched sets separate)

* phase that makes the # of chromosomes reduced to 23 (from 46)

in meiosis

- homologous chromosomes finish separating

- cytokinesis

- nucleus forms

in mitosis, the phase when:

• - Chromosomes finally get to separate poles
• - chromosomes decondense
• - nuclear envelope reforms
• - cytokenisis (division of cytoplasm) is complete

separation into 2 cells with 1/2 the original number of chromosomes.

occurs during telophase

the arrangement of chromosomes based on physical characteristics i.e. length and location of the centromere

can be checked for defects in number or structure of chromosomes

the condition of having one set of chromosomes, as in eggs and sperm

sex cell division: separatation of homologues

• - 2 step process (M₁ and M₂)
• - Results in 4 genetically different "daughter cells"
• - production of male and female gametes

coming together of homologous chromosomes that occurs during prophase 1 of meiosis.

occurs to form a tetrad

exchange of alleles between non-sister chromatids

- allows for genetic recombination/variability

occurs within chiasmata (overlaping)

- DOES NOT always happen

- positioning of homologous pairs is random

- resulting daughter cells have combination of mom and dad chromosomes

an important source of genetic variation

During Anaphase I or II . . .

• - pair of homologues Don't Separate
• - sister chromatids Don't Separate

results in sex cells with an abnormal number of chromosomes

a condition in which there are 3 representatives of a chromosome instead of only 2 representatives

a condition in which there is only 1 representative of a chromosome instead of 2 representatives

2 Purposes of meiosis

in meiosis: n+n=2n

- allows 2 cells to come together to form 1 diploid

- otherwise there will be polyploidy condition

in meiosis:

- crossing over

- independent assortment