Chromosomes- Mitosis & Meiosis

MCB 2410

Chromosome complement

the complete set of chromosomes of plants and animals

Somatic cells

body cells

Diploid

containing two similar sets of chromosomes

Germ cells

gametes

Germ cells contain…

one set of chromosomes, haploid

Mitosis

a precise process of nuclear division that ensures that each of two daughter cells receives a diploid complement of chromosomes identical with the diploid complement of the parent cell

Cytokinesis

the process in which the cell itself divides to yield two daughter cells

Interphase

stage where a cell is not undergoing mitosis

S phase

DNA synthesis (replicated)

What occurs before or after S?

G1 & G2

What are the three parts of interphase?

S, G1, G2

What phase is interphase followed by?

M phase

Prophase

condensation of chromosomes

Chromatids

two subunits in chromosomes

Centromere

the chromatids in a pair are held together at a specific
region of the chromosome

Metaphase

Mitotic spindle forms

What does the spindle consist of?

microtubules

Kinetochore

the spindle fibers attach to each chromosome in the
region of the centromere

Microtubules

A narrow, hollow, tube-like structure found in the cytoplasm

Metaphase plate

an imaginary plane equidistant from the spindle poles

Anaphase

centromeres divide longitudinally, and the two sister chromatids of each chromosome move toward opposite poles of the spindle

Telophase

a nuclear envelope forms around each compact group of chromosomes, nucleoli are formed, and the spindle disappears; chromosomes undergo decondensation

Meiosis

a mode of cell division in which cells are created that contain only one member of each pair of chromosomes

Meiosis consists of how many successive nuclear divisions?

two

What does Meiosis result in?

four daughter cells, each genetically different and each containing one haploid set of chromosomes

Meiocytes

the location of where meiosis takes place in animals

Oocytes

form egg cells

Spermatocytes

form sperm cells

Synapsis

Prior to the first nuclear division, the members of each pair of chromosomes become closely associated along their length

Homologous chromosomes

chromosomes that pair with each other

four-stranded structure

tetrad or bivalent

Crossing over

At the time of pairing, the homologs can exchange genes that results in chromosomes that consist of segments from one homolog intermixed with segments from the other

Meiosis I

the homologous chromosomes are separated from each other, one member of each pair going to opposite poles of the spindle

What does not occur in Meiosis II?

DNA replication

The first meiotic division (Meiosis I) is also called…

reductional division

What occurs in Prophase I?

Chromosomal condensation, Synapsis of duplicated homologous chromosomes, crossing over between non sister chromatids of homologous pairs

Sister chromatids

identical copies within a duplicated chromosome

Nonsister chromatids

paternal and maternal chromatids within a tetrad (not identical, but the same)

Chiasma

X-shaped structure during crossing over

How do genes on different chromosomes undergo independent assortment?

Nonhomologous chromosomes align at random in metaphase I

The physical separation of homologous chromosomes in anaphase I is the physical basis of?

Mendel’s principle of segregation

Meiosis II is also called the…

equational division

Chromatin

Eukaryotic chromosomes are highly coiled stable
complexes of DNA and protein

The nucleosome is the basic structural unit of…

Chromatin

Histones

small proteins that are highly conserved among different organisms

Heterochromatin

Compact and heavily stained regions of chromatin, which mainly consists of highly repeated noncoding DNA sequences (Satellite DNA)

Satellite DNA

highly repeated noncoding DNA sequences

euchromatin

becomes visible only after chromosome condensation in mitosis or meiosis

The centromere is essential for..

chromosome segregation

The telomere is essential for…

the stability of the chromosome tips

Due to the nature of DNA replication, chromosomes require special mechanism to restore DNA in telomeres in each cycle of replication. This mechanism relies on an enzyme called…

telomerase